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Choice Procedures in Pairwise Comparison Multiple-Attribute Decision Making Methods We consider extensions of some classical rational axioms introduced in conventional choice theory to valued preference relations. The concept of kernel is revisited using two ways : one proposes to determine kernels with a degree of qualification and the other presents a fuzzy kernel where every element of the support belongs to the rational choice set with a membership degree. Links between the two approaches is emphasized. We exploit these results in Multiple-attribute Decision Aid to determine the good and bad choices. All the results are valid if the valued preference relations are evaluated on a finite ordinal scale. Introduction We consider a pair wise comparison multiple-attribute decision making procedure that assigns to each ordered pair (x, y), x, y ∈ A (the set of alternatives) a global degree of preference R(x, y). R(x, y) represents the degree to which x is weakly preferred to y. We suppose that R(x, y) belongs to a finite set L : {c 0 , c 1 , . . . , c m , . . . , c 2m } that constitutes a (2m + 1)-element chain {c 0 , c 1 , . . . , c 2m }. R(x, y) may be understood as the level of credibility that "a is at least as good as b". The set L is built using the values of R taking into consideration an antitone unary contradiction operator ¬ such that ¬c i = c (2m−i) for i = 0, | 3,069,300 | 17933865 | 0 | 16 |
. . . , 2m. If R(x, y) is one of the elements of L, then automatically ¬R(x, y) belongs to L. We call such a relation an L-valued binary relation. We denote L m : {c m+1 , . . . , c 2m } and L ≺m : {c 0 , . . . , c m−1 }. If R(x, y) ∈ L m , we say that the proposition "(x, y) ∈ R" is L-true. If however R(x, y) ∈ L ≺m , we say that the proposition is L-false. If R(x, y) = c m , the median level (a fix point of the negation operator) then the proposition "(x, y) ∈ R" is L-undetermined. If R(a, b) = c r and R(c, d) = c s , c r < c s , it means that the proposition "a is at least as good as b" is less credible than "c is at least as good as d". In the classical case where R is a crisp binary relation (m = 2, and R(x, y) is never rated c 1 ; R(x, y) = c 2 = 1 is denoted xRy and R(x, y) = c 0 = 0 corresponds to ¬xRy, we define a digraph G(A, R) with vertex set A and arc family R. A choice in G(A, R) is a non empty set Y of A. R can be represented by a Boolean matrix and the choice Y can be defined with the use of a subset characteristic | 3,069,301 | 17933865 | 0 | 16 |
row vector The subset characteristic vector of the successors of the elements of the vertex set Y : {x ∈ A | ∃ y ∈ Y, yRx} is denoted Y •R and is obtained using the Boolean composition where ∨ and ∧ represent respectively "disjunction" and "conjunction" for the 2-element Boolean lattice B = {0, 1}. The choice Y should satisfy some of the following rationality axioms (Ȳ represents the complement of Y in A): • Inaccessibility of Y (or GOCHA rule, cf. [5], [10]) ∀y ∈ Y, ∀x ∈Ȳ , ¬xRȳ Y • R ⊆Ȳ , "the successors ofȲ are insideȲ ". • Stability of Y (see [9], [11]) ∀y ∈ Y, ∀x ∈ Y, ¬yRx Y • R ⊆Ȳ , "the successors of Y are insideȲ ". • Dominance of Y (or external stability, see [9], [11]) ∀x ∈Ȳ , ∃ y ∈ Y, yRx Y ⊆ Y • R, "the successors of Y containȲ ". • Strong dominance of Y (or GETCHA rule, cf. [5], [10]) ∀y ∈ Y, ∀x ∈Ȳ , yRx ≡ ¬yR d x (R d is the dual relation, i.e. the transpose of the complement of R) The maximal set of all non-dominated alternatives (inaccessibility and stability are satisfied) is called the core of Y and the internally and externally stable set corresponds to the kernel. The GETCHA set is such that the strong dominance rule applies. No specific property like acyclicity or antisymmetry will be assumed in the sequel. The core guarantees a rather small choice but is | 3,069,302 | 17933865 | 0 | 16 |
often empty. The GETCHA set corresponds to a rather large set and, in this general framework, the kernel (see [5], [8]) seems to be the best compromise. However its existence or uniqueness cannot be guaranteed. . It has been mentioned in [5] that for random graphs -with probability .5 -a kernel almost certainly exists and that in a Moon-Moser graph with n nodes the number of kernels is around 3 n/3 . In order to illustrate all these concepts, we consider a small example. Example 1 Consider the following example with 8 alternatives: A : {a, b, c, d, e, f, g, h}. The Boolean matrix R together with the outgoing and ingoing scores S(+) and S(−) are presented in Table 1. 3 7 7 7 6 2 5 6 We may define generalizations of the previous crisp concepts in the valued case in two different ways: (i) Starting from the definition of a rational choice in terms of logical predicates, one might consider that every subset of A is a rational choice with a given qualification and determine those sets with a sufficient degree of qualification. (ii) One might also extend the algebraic definition of a rational choice. In that case, there is a need to define proper extensions of composition law • and inclusion ⊆. Solutions that correspond to this approach give a fuzzy rational setỸ , each element of A belonging to A to a certain degree (membership function). It should be interesting to stress the correspondence between these two approaches. The choice | 3,069,303 | 17933865 | 0 | 16 |
of the operators is closely related to the type of scale that is used to quantify the valued binary relation R, i.e. an ordinal scale. Qualification of crisp kernels in the valued ordinal context We now denote G L = G L (A, R) a digraph with vertices set A and a valued arc family that corresponds to the L-valued binary relation R . This graph is often called outranking graph in the context of multi-attribute decision making. We define the level of stability qualification of subset Y of X as Y is considered to be an L-good choice, i.e L-stable and L-dominant , if ∆ sta (Y ) ∈ L m and ∆ dom (Y ) ∈ L m . Its qualification corresponds to We denote C good (G L ) the possibly empty set of L-good choices in G L . The determination of this set is an NP-complete problem even if, following a result of Kitainik [5], we do not have to enumerate the elements of the power set of A but only have to consider the kernels of the corresponding crisp strict median-level cut relation R m associated to R, i.e. (x, y) ∈ R m if R(x, y) ∈ L m . As the kernel in G(X, R m ) is by definition a stable and dominant crisp subset of A, we consider the possibly empty set of kernels of G m = G(A, R m ) which we denote C good (G m ). Kitainik proved that The determination of | 3,069,304 | 17933865 | 0 | 16 |
crisp kernels has been extensively described in the literature (see, for example [9]) and the definition of C good (G L ) is reduced to the enumeration of the elements of C good (G m ) and the calculation of their qualification. Example 2 We now consider the comparison of 8 cars (a, b, c, d, e, f, g) on the basis of maximum speed, volume, price and consumption. Data and aggregation procedure will not be presented here (for more details, see [2]). The related outranking relation is presented in Table 2. We will consider only the ordinal content of that outranking relation and we transpose the data on a L-scale with c 0 = 0, c 2m = 1, m = 27 and c m = .5. The strict median-cut relation R m corresponds to data of Table 1. The set C good (G m ) corresponds to ({b}, {a, f }, {a, g}) with the following qualifications: Fuzzy kernels A second approach to the problem of determining a good choice is to consider the valued extension of the Boolean system of equations (1). IfỸ (.) = (. . . , Y (x), Y (y), . . . ), whereỸ (x) belongs to L for every x ∈ A is the characteristic vector of a fuzzy choice and indicates the credibility level of the assertion that "x is part of the choiceỸ ", we have to solve the following system of equations: The set of solutions to the system of equations (2) is calledỸ dom | 3,069,305 | 17933865 | 0 | 16 |
(G L ). In order to compare these fuzzy solutions to the solutions obtained in C good (G L ), we define the crisp choice and we consider a partial order on the elements ofỸ dom (G L ) :Ỹ is sharper thañ The subset of the sharpest solutions inỸ dom (G L ) is called F dom (G L ). Bisdorff and Roubens have proved that the set of crisp choices constructed from F dom (G L ) using (3) and denoted K(F dom (G L )) coincides with C dom (G L ). Coming back to Example 2, we obtain 3 sharpest solutions to equation (2 In this particular case, we obtain only Q good and ¬Q good as components of theỸ 's but this is not true in general. Good and bad choices in Multi-attribute decision making In the framework of decision making procedures, it is often interesting to determine choice sets that correspond to bad choices. These bad choices should be ideally different from the good choices. To clarify this point, let us first consider the crisp Boolean case and define the rationality axiom of • Absorbance of Y (see [10]) ∀x ∈Ȳ , ∃ y ∈ Y, xRy = yR t x Y ⊆ Y • R t , "the predecessors of Y containȲ ". As the stability property can be rewritten as Y • R t ⊆Ȳ , we immediately obtain the Boolean equation that determines the absorbent kernel (stable and absorbent choice):Ȳ We notice that for some digraphs (dominant) | 3,069,306 | 17933865 | 0 | 16 |
kernels and absorbent kernels may coincide (consider a digraph G(A, R) with vertices A : {a, b, c, d} and four arcs (a, b), (b, c), (c, d), (d, a). {a, c} as well as {b, d} are dominant and absorbent kernels or good and bad choices). This last concept can be easily extended in the valued case. Consider the valued graph G L introduced in Section 2. We define the level of absorbance qualification of Y as The qualification of Y being a bad choice corresponds to The set of solutions of equations (4) denotedỸ abs (G L ) can be handled in the same way as done in Section 3 forỸ dom (G L ) and creates a link between these solutions (4) and subsets of Y being qualified as bad choices. Reconsidering We finally decide to keep car b as the best solution noticing however that it is a bad choice. Going back to digraph G(A, R m ), we see that b is at the same time dominating and dominated by all the other elements. Car b is indifferent to all the other cars which is not true for a, c, d, e, f, g, h, since indifference is not transitive in this example. | 3,069,307 | 17933865 | 0 | 16 |
EEG Resting Asymmetries and Frequency Oscillations in Approach / Avoidance Personality Traits: A Systematic Review : Background: Brain cortical activity in resting electroencephalogram (EEG) recordings can be considered as measures of latent individual disposition to approach / avoidance behavior. This systematic review aims to provide an updated overview of the relationship between resting EEG cortical activity and approach / avoidance motivation personality traits. Methods: The review process was conducted according to the PRISMA-Statement, using PsycArticles, MEDLINE, Scopus, Science Citation Index, and Research Gate database. Restrictions were made by selecting EEG studies conducted in resting idling conditions, which included approach / avoidance personality traits or parallel measures, and an index of EEG brain activity. In the review 50 studies were selected, wherein 7120 healthy adult individuals participated. Results: The study of the relationship between resting EEG cortical activity and approach / avoidance personality traits provides controversial and unclear results. Therefore, the validity of resting asymmetry or frequency oscillations as a potential marker for approach / avoidance personality traits is not supported. Conclusions: There are important contextual and interactional factors not taken into account by researchers that could mediate or moderate this relationship or prove it scarcely replicable. Further, it would be necessary to conduct more sessions of EEG recordings in di ff erent seasons of the year to test the validity and the reliability of the neurobiological of pre-cap statistically controlled. a shift toward a more negative mood Negative mood post-preparation, but not pre-preparation, predicted relative left frontal activation in Introduction Brain frequency oscillatory activity is defined | 3,069,308 | 225113911 | 0 | 16 |
as the real activity of the brain [1]. According to Klimesch [2], slow rhythms (delta and theta bands) have more ancient phylogenetic origin than fast rhythms (alpha, beta, gamma bands). Delta rhythm is dominant in reptiles, theta rhythm is dominant in the lower mammals, and alpha is defined as the dominant rhythm in adult humans. The EEG alpha power at the frontal scalp is the gold standard measure used to evaluate functional inter-hemispheric asymmetry. According to Davidson [3] and Harmon-Jones [4], higher relative left frontal cortex activity is related to behavioral approach and positive emotions, whereas higher relative right frontal cortex activity is related to behavioral avoidance and negative emotions. Furthermore, according to Harmon-Jones and Gable [5], baseline electroencephalogram (EEG) measures in idling condition can be treated as personality dispositions. In this conceptual framework, the test-retest reliability of the resting EEG is comparable to the test-retest of self-reported personality trait measures, recorded in idling standard experimental conditions [6]. Thus, brain alpha oscillations can be considered as the measure of latent individual disposition to a specific style of behavior. However, the replicability of these associations with approach/avoidance personality traits is still unclear [7]. The same can be Research Strategies The research of literature was conducted on the international electronic databases, PsycArticles, MEDLINE, Scopus, and Science Citation Index. The last research of international literature was completed in June 2020. In this work were included peer-reviewed full-text journal articles, written in English or Italian. The investigation was delimited to studies conducted on healthy adult human samples without restrictions to | 3,069,309 | 225113911 | 0 | 16 |
gender or ethnicity. These studies considered the relationship or association among EEG measure/s such as cortical asymmetry (e.g., frontal or posterior), frequency oscillations, synchronization or desynchronization of EEG rhythms, and personality traits such as approach/avoidance personality traits (behavioral inhibition system "BIS", behavioral approach system "BAS", fight-flight system "FFS" or fight-flight-freeze system "FFFS") and/or their parallel measures (e.g., positive affect, extraversion, sensation seeking, negative affect, neuroticism, fear or state anxiety), in a resting state idling experimental condition. The research on electronic database was conducted including the following terms or keywords: 1. Asymmetry and brain activity: "EEG asymmetry" OR left OR right OR lateral* OR front* OR posterior OR prefrontal OR parietal* OR electroenceph* OR oscill* OR rhythms OR coupling OR "frequency oscillations" OR synchronization OR desynchronization OR alpha OR delta OR theta OR beta OR gamma AND rest*; 2. Approach/avoidance motivation: "approach motivation" OR motivation* OR approach* OR BAS OR reward* OR "positive affect" OR "avoidance motivation" OR avoid* OR "negative affect" OR BIS OR withdraw* OR inhibit* OR threat* OR fear OR FFS OR FFFS. Eligibility Criteria The results of the systematic research were examined by two authors (A.V.-Ph.D. student; V.D.P.-Ph.D. Tutor). A first articles' exclusion was done by title and abstract reading, according to the following eligibility criteria: (i) EEG study conducted in resting state idling condition, only. This criterion led to the exclusion of the studies in which the participants were presented acoustic sounds [11], debated an oral presentation [12], and the resting-state EEG was recorded after physical exercise [13], after the induction of | 3,069,310 | 225113911 | 0 | 16 |
a negative mood [14], or stress condition by experimenter [15]. Measures of asymmetry and frequency oscillations recorded during hypnotic-state condition were excluded [16]. Furthermore, studies were excluded that (i) had considered resting-state EEG asymmetries or frequency oscillations as comparison measures to predict brain activity during a behavioral test [17][18][19]; (ii) report almost a self-report measure of approach/avoidance personality trait or parallel measures. This criterion excluded the studies that conceptualized EEG asymmetry as a latent state-latent trait in the absence of the self-report (e.g., [20]); (iii) involved healthy adult individuals. This criterion led to the exclusion of research conducted on a sample of preadolescents (e.g., [21]), and EEG studies conducted on clinically relevant mental disorders and other illnesses, such as Alzheimer's and Parkinson's disease, Down's syndrome, chronic pain, mild cognitive impairment, and Williams' syndrome. In the first phase of screening, in order to not omit important research, the inclusion of studies by title and abstract readings were carried out independently by the two authors. Later, after the authors had reached a joint agreement, the first author (A.V.) examined in more depth the content of all articles that met the eligibility requirements, then moved on to the data extraction. The second author (V.D.P) supervised the data extraction to ensure it was performed correctly and carefully, and according to the eligibility criteria selected. Data Collection and Quality Assessment According to the PICOS approach [9,10], data collections were assessed by including in the selected studies: sample characteristics (i.e., sample size, gender, age, and education of participants); experimental design and used | 3,069,311 | 225113911 | 0 | 16 |
methods across studies; instruments used to measure personality traits of approach/avoidance motivation and parallel measures; the self-report scores; statistical analyses; and obtained results. Two authors (A.V. and V.D.P.), independently, evaluated the risk of bias analysis. According to the criteria considered in the Cochrane Handbook for Systematic Reviews of Interventions [22,23], the second author (V.D.P.) blinded the articles selected by the first author (A.V). Therefore, the title of the study, the name of the journal, and the name of the authors were unknown to the first author (A.V.) who executed the evaluation of the articles. The quality assessment was conducted using the Joanna Briggs Institute (JBI) Critical Appraisal checklist for Analytical Cross-Sectional studies [24], modified ad hoc by considering the under-reported criteria and the aim of this review. According to Hagemann [25], different criteria adopted to EEG recording, such as referencing, analysis, and multiple sessions of measurement, represent some classical issues for resting-EEG measure validity and reliability. Thus, to evaluate the quality assessment for each selected study, the resting EEG recording method used and potential EEG fluctuations due to the state-condition changes were considered. In line with this conceptual background, the final form of checklist consists of the six domains: (1) Adequacy of the criteria adopted for the inclusion of participants in the sample (absence of clinical psychological disorders or other diseases, suspension of drug or psychotropic substances in case used); (2) Sample and setting characteristics (mean age and standard deviation, gender, education, and handedness); (3) Methodological criteria used for the electrophysiological measures (open or closed eyes | 3,069,312 | 225113911 | 0 | 16 |
recording, reference, length, counterbalance between open/closed eyes order and participants); (4) Occurrence of contextual or interactional variables not considered in the study that could constitute confounding factors (time of day and season of EEG recording, measures of mood state before and during EEG recording, menstrual cycle for women, and gender of experimenters); (5) Reliability of electrophysiological measures (test-retest sessions of EEG recording); (6) Adequacy of the statistical analysis used (including the strategies to deal with confounding factors considered in the study). For each research article, the methodological quality assessment was determined for each domain as low, partial, and high risk of bias (respectively, "0", "1", "2"), by calculating the mean score multiplied by 100. Then a cut-off level of 75% was established. The studies under or equal to 75% were considered as low risk of bias, while, the studies above 75% were considered as high risk of bias. Table 1 shows the data extracted and examined for each study included. [113]; xx Strelau Temperament Inventory [114]; xxx Rusalov Structure of Temperament Questionnaire [115]; y Interpersonal Adjective Scales (IAS-R, [116]); z Trait Emotional Intelligence Questionnaire [117]. Studies Selection The flow chart ( Figure 1) provides an accurate summary of the quality assessment of the articles identified through databases. The bibliographic research included all combinations of keywords and produced 5313 results. Furthermore, two additional articles were identified through other sources and included in this article. Later, duplicated studies were removed and after title and abstract readings, 2937 full-text articles were included. According to the eligibility criteria, 152 articles | 3,069,313 | 225113911 | 0 | 16 |
were reviewed by full-text screening and, consequently, 101 articles were excluded with reason. Finally, 47 articles, for a total of 50 studies, were passed to the quality assessment and were thus included in the systematic review. Studies Selection The flow chart ( Figure 1) provides an accurate summary of the quality assessment of the articles identified through databases. The bibliographic research included all combinations of keywords and produced 5313 results. Furthermore, two additional articles were identified through other sources and included in this article. Later, duplicated studies were removed and after title and abstract readings, 2937 full-text articles were included. According to the eligibility criteria, 152 articles were reviewed by full-text screening and, consequently, 101 articles were excluded with reason. Finally, 47 articles, for a total of 50 studies, were passed to the quality assessment and were thus included in the systematic review. Figure 2 shows the percentage of studies and articles included for the quality of the assessed criteria. Generally, 44 studies (88%) presented low scores on the risk of bias, while six studies (12%) showed high scores. A large percentage of the studies used valid methodological criteria for measuring EEG performance in idling condition and included an appropriate sample size. However, many researchers did not report controlled criteria for the inclusion of the participants in their studies (first domain), did not consider interactional or confounding variables that could influence the reliability of the evaluated relations (fourth domain) and, furthermore, they did not test-retest sessions of their EEG measures (fifth domain). These are the three | 3,069,314 | 225113911 | 0 | 16 |
domains in which risk of bias was subjectively evaluated as higher than the other domains. In contrast, statistical analysis was adequate to the outcome studied (see Figure 2). Figure 2 shows the percentage of studies and articles included for the quality of the assessed criteria. Generally, 44 studies (88%) presented low scores on the risk of bias, while six studies (12%) showed high scores. A large percentage of the studies used valid methodological criteria for measuring EEG performance in idling condition and included an appropriate sample size. However, many researchers did not report controlled criteria for the inclusion of the participants in their studies (first domain), did not consider interactional or confounding variables that could influence the reliability of the evaluated relations (fourth domain) and, furthermore, they did not test-retest sessions of their EEG measures (fifth domain). These are the three domains in which risk of bias was subjectively evaluated as higher than the other domains. In contrast, statistical analysis was adequate to the outcome studied (see Figure 2). Approach/Avoidance Personality Traits and Electrocortical Measures Approach/avoidance personality traits represent long-term stable behavioral state patterns [118]. The first version of the reinforcement sensitivity theory (RST), conceptualized from animal behavior by Gray, was an extension of the theory originally postulated by Eysenck. This theory posited three systems responsible for behavior: (1) the behavioral inhibition system (BIS); (2) the behavioral approach system (BAS); (3) a not well-defined fight-flight system (FFS) activated by fear [119]. Later, Gray inserted the response of block or freeze into the FFS, and reconceptualized this | 3,069,315 | 225113911 | 0 | 16 |
system into the fight-flight-freeze system (FFFS) as the main system responsible for fear responses. The FFFS is activated only in the case of active avoidance of a threatening stimulus (escape) while, if the situation requires an attack on the threat, both the BIS and the FFFS are activated (fight). According to the motivational model theory [119,120], a relatively greater left-frontal activity is associated with behavior that results in approaching or engaging a stimulus and is related to higher Approach/Avoidance Personality Traits and Electrocortical Measures Approach/avoidance personality traits represent long-term stable behavioral state patterns [118]. The first version of the reinforcement sensitivity theory (RST), conceptualized from animal behavior by Gray, was an extension of the theory originally postulated by Eysenck. This theory posited three systems responsible for behavior: (1) the behavioral inhibition system (BIS); (2) the behavioral approach system (BAS); (3) a not well-defined fight-flight system (FFS) activated by fear [119]. Later, Gray inserted the response of block or freeze into the FFS, and reconceptualized this system into the fight-flight-freeze system (FFFS) as the main system responsible for fear responses. The FFFS is activated only in the case of active avoidance of a threatening stimulus (escape) while, if the situation requires an attack on the threat, both the BIS and the FFFS are activated (fight). According to the motivational model theory [119,120], a relatively greater left-frontal activity is associated with behavior that results in approaching or engaging a stimulus and is related to higher levels of behavioral approach (BAS), while a relatively greater right-frontal activity leads to | 3,069,316 | 225113911 | 0 | 16 |
the disengagement from a stimulus and is related to higher levels of withdrawal behavior. The reinforcement sensitivity theory [121] and the motivational model [122] inspired many researchers to study the behavioral underpins in terms of neurobiological markers. Carver and White [82], using the systems conceptualized by Gray [123,124], structured the BIS/BAS scale [82] to assess the motivational model of frontal EEG asymmetry proposed by Davidson [122]. However, the problem with the BIS/BAS scales questionnaire was the lack of separation of the FFFS and the BIS, which may account for inconsistent findings obtained in past research when the BIS scale was related to resting frontal alpha activity. Recently, Neal and Gable [64] derived BIS and FFFS subscales from the original Carver and White's scale [82], demonstrating that the BIS subscale, but not the FFFS, related to greater relative right frontal activity, and that a measure of impulsivity related to the smaller right frontal activity. However, in this vein, the most important revision was done by Corr [125] in his revised RST (r-RST), which produced the development of the Reinforcement Sensitivity Theory Personality Questionnaire "RST-PQ" [89]. In the r-RST, the function of the BIS is primarily to detect and resolve conflicts between the BAS and FFFS. In addition, in the r-RST, the BAS is reconceptualized as a multidimensional system [126] composed of the subcomponents reward interest (RI), goal-driven persistence (GDP), reward reactivity (RR), and impulsivity (Imp). Another contribution to the definition of personality was conceptualized by Costa and McCrae who proposed the Big Five model [127]. This descriptive | 3,069,317 | 225113911 | 0 | 16 |
model defined the following five stable factors, considered as the basic vectors of the personality structure: conscientiousness; extraversion; emotional stability/instability; openness; agreeableness. Although r-RST is a neurobiological theory and the Big Five model is descriptive, there are meeting points between the two. According to Smits and De Boeck [128], extraversion can be explained by the BAS trait, while, emotional instability (or neuroticism), can be explained by the BIS trait. Therefore, in this framework, a lot of individual disposition and state variables can be considered as parallel measures of the BIS, BAS, and FFFS motivational personality traits. In line with this point of view, many studies have investigated the relationship between the hemispheric asymmetry of the EEG asymmetrical activation of the brain delta, theta, alpha, beta, and gamma rhythms and the approach/avoidance behavioral traits. All the studies included in this review assessed one or more measures of approach/avoidance personality traits and parallel, or related, measures. In particular, 16 articles considered the relation among resting-EEG activity and BIS/BAS personality traits [8,28,33,34,37,46], [48] (in study 2), [49,51,57,59,64,66,67,69,70]. The association between resting-EEG activity and FFFS, was considered in four articles [64,66,67,69], but, of these, only two studies found significative results [64,66]. Furthermore, one study considered the relation among EEG gamma activity and autistic traits [65], one article studied the role of resilience [68], and two articles found a positive association between EEG alpha activity and emotional intelligence [39,50]. Some studies have observed a significant relation between autistic traits and approach/avoidance personality traits [129], as well as emotional intelligence [130] and | 3,069,318 | 225113911 | 0 | 16 |
resilience [131]. In particular, results have shown a negative correlation between resilience and the brain network flexibility for the delta, alpha, and beta bands, suggesting a robust relationship among the flexibility of human brain and resilience traits [68]. Finally, one study included in this review considered the relation between EEG activity and transliminality [41]. Approach/Avoidance Personality Traits and EEG Gamma Rhythm Although there is still no univocal agreement among researchers regarding on the definition of EEG gamma band, in general it is referred to as the range of frequencies comprised between 30 and 70 Hz [132]. In particular, recent research classifies a slow gamma activity as being around 20-40 Hz, and a fast gamma activity as around 40-70 Hz, generated from excitatory-inhibitory interactions of pyramidal cell and interneuron networks [133] in posterior brain regions [134], visual cortex [135], temporal-parietal regions [136], and the hippocampus [137]. Furthermore, according to Fries [138], the synchronization of the gamma frequency would be involved in the synchronization of the alpha-beta feedback signal in the cortical networks. With regard to the study of brain oscillations and personality, Jaušovec and Jaušovec [39] investigated the relationship among Big Five personality traits [94], emotional intelligence, and EEG activity in right-handed participants during an eyes-closed resting period. In this study, these authors, taking into account the role of gender, analyzed the EEG rhythms using entropy measures, fast Fourier transform (FFT), and low-resolution electromagnetic tomography (LORETA) techniques. Results highlighted that brain activity was increased in the parieto-occipital areas rather in the frontal area only for compounds among | 3,069,319 | 225113911 | 0 | 16 |
extreme personality styles (neurotic type, low emotional intelligence and agreeableness; high neuroticism, or specific combinations of personality dimensions, e.g., introverts with high emotional IQ, versus extraverts with low to average IQ). These compounds were related to the spectrum of gamma-band activity and gender [39]. Openness to experience (O-Big Five trait) has been found to be associated with transiliminality [139]. This trait has been defined as "susceptibility to, and awareness of, large volumes of imagery, ideation, and affect. These phenomena can be generated by subliminal, supraliminal, or external input" [140] (p. 327). In a recent study, Fleck and colleagues [41] studied the association among transliminality and frequency oscillations, suggesting that higher levels of transliminality are related to lower slow alpha, beta, and gamma-band activity in the left posterior cortex and lower fast alpha, lower beta, and gamma activity in the right superior temporal areas. Moreover, lower levels of transliminality were related to increased gamma-band in the mid frontal areas, than higher levels of this trait [41]. In addition to studying the relationship among personality traits and gamma-band activity, many researchers have been interested in studying the relationship within brain traits and the development of cognitive processes between personality traits. Many studies found that gamma-band activity is related to cognitive functions [141], such as perceptual binding [142], attention [143], working memory [144], language [145], and social interaction [146]. According to Groot and Van Strien [65], these domains are altered in the autism spectrum disorder (ASD). Recent studies assess that individuals with ASD have increased spontaneous gamma oscillations [147]. | 3,069,320 | 225113911 | 0 | 16 |
Thus, according to these studies and the autism spectrum hypothesis [74], De Groot and Van Strien [65] hypothesized that enhanced gamma-band activity could be considered as a biomarker of ASD-an endophenotype present in people with higher levels of autistic traits. To confute this supposition, the authors administered the Autism-Spectrum Quotient (AQ) questionnaire [74] to right-handed male and female university students and recorded their EEG activity during a resting idling condition. In this sample, results suggested that gamma power was not related to the autistic quotient "AQ" score. This result may be due to the fact that autistic traits in the general population are not strong enough to be detected [65]. In sum, the number of reports referring to the relationship between resting EEG gamma-band activity and personality traits is so limited that they cannot be discussed in depth within a context of motivational theory [3,4,89]. Thus, among the articles included in this review, only three [39,41,65] analyzed the relation between personality traits and EEG gamma-band activity. However, we believe it is important to highlight and reflect on these poor results to inspire future research exploring this relationship further. In terms of the anxiety trait, Pavlenko and colleagues [47] studied the relation among resting EEG oscillations in healthy adult male/female participants, and personality measures of state and trait anxiety. Results highlighted, in only two studies, that state anxiety was positively correlated with the spectral power density (SPD) of central beta-band in the temporal and occipital regions of the right-hemisphere during the eyes-open recording. Moreover, the correlations of | 3,069,321 | 225113911 | 0 | 16 |
the estimates of trait anxiety with the SPDs of the beta rhythm were found in frontal and central areas of both hemispheres and parietal and occipital loci of the right hemisphere. Anxiety trait was positively correlated with the SPDs of the slow and central beta-band oscillations [47]. These results are partially in line with approach/avoidance motivational theory in which the behavioral inhibition, or its parallel anxiety measures, are associated with a greater relative right frontal cortical activation [28,64]. According to Threadgill and Gable [67], the beta activity during resting state can be assumed as a neurophysiological marker of motivated motor-action preparation. In their experiment, the authors first assessed, in a sample of university students, the behavioral approach/avoidance motivational traits (BIS/BAS Scale [82]) and the Impulsive Behavior Scale of the Regulatory Control Questionnaire (UPPS-P [90]), to evaluate the influence of behavioral disinhibition. They then recorded the EEG in a resting idling condition. In this sample, results emphasized that a greater trait approach was negatively associated with resting beta activity, while greater trait impulsivity was associated with a greater resting beta activity. Lower levels of resting beta activity in the motor cortex was found associated with traits related to motivated motor behaviors. Furthermore, according to Schutter and colleagues [8], frontal EEG asymmetry of beta activity (13-30 Hz) reflects the brain cortical excitability and approach-avoidance motivational predispositions. In this study, frontal asymmetry is a direct measure of cortical excitability and is seen in line with the approach/avoidance motivational model proposed by Davidson [3], wherein self-reported emotional tendencies for approach | 3,069,322 | 225113911 | 0 | 16 |
or avoidance are associated, respectively, with left-or right frontal asymmetry. In sum, resting EEG beta asymmetry findings from the above-mentioned three studies included in this review are in line with our initial hypotheses. These findings indicated that in resting idling conditions, the beta frontal asymmetry [8,47,67] and the scalp-distributed beta activity can be defined as potential markers of the approach/avoidance motivation personality traits. Approach/Avoidance Personality Trait, Interactional Variables, and EEG Alpha Rhythm Alpha rhythm, or Berger's rhythm, is a brain activity with a frequency ranging from 8 to 13 Hz, associated with a state of wakeful relaxation [162]. This rhythm is classified in slow alpha (8-10 Hz), generated in the anterior brain regions, and fast alpha (11)(12)(13), generated in the posterior regions [163]. The anterior and posterior systems constitute a single alpha network, distributed over the whole brain surface [164]. Moreover, the alpha rhythm is considered as a mechanism of surrounding inhibition [165], useful in increasing the signal-noise ratio and to inhibit ongoing conflicting processes [2]. According to the "idling condition hypothesis", alpha activity reflects both the ongoing cognitive processes and the proper inhibitory mechanisms of this condition. This characterizes alpha activity as a good biological index sensitive to personality and behavior differences among individuals [166]. The association between alpha rhythm and the approach/avoidance behavioral traits was studied in more depth than other EEG rhythms. In this review of the literature, 33 studies that found a relationship between resting-EEG alpha rhythm and approach/avoidance behavioral traits, or other parallel trait measures were included. Of these studies, 27 | 3,069,323 | 225113911 | 0 | 16 |
analyzed the relationship among EEG alpha activity and approach/avoidance personality traits [26][27][28][29][30]33,[35][36][37][38][39][40][42][43][44], [45] (studies 1 and 2), [46,50], [52] (studies 3 and 4), [57,59,[62][63][64]71], while, the remaining six studies analyzed the influence of the interactional or contextual variables, on the relationship between approach/avoidance personality traits and resting EEG alpha activity [31,32], [48] (studies 1 and 2), [60,66]. For this reason, we decided to discuss the results highlighted by this research line in two separate sections. In the first section, we review findings on the relationship between resting EEG alpha activity and approach/avoidance personality traits. In the second section of this paragraph, we review findings supporting the influence of interactional or contextual variables on this relationship. Approach/Avoidance Personality Traits and EEG Alpha Rhythm The measure of EEG alpha spectral power, in the frontal area, is used to calculate an index of inter-hemispheric frontal asymmetry in resting condition. This index is usually calculated by subtracting the resting EEG alpha power of the cortical area of interest in the left hemisphere from that of the homologous area in the right hemisphere [167]. In a pioneer research, Tomarken and colleagues [26] found that resting EEG anterior alpha asymmetry, recorded in a sample of adult women, was related to individual differences in positive and negative affect (PA, NA) traits. In particular, they found that the activation of the anterior left hemisphere was related to relatively frontal higher levels of PA scores, while lower levels of NA were associated with an increased right hemisphere anterior activation [26]. The relation among resting EEG | 3,069,324 | 225113911 | 0 | 16 |
alpha asymmetry and positive/negative emotional traits (PA, NA) was labelled as the "emotional model" of hemispheric asymmetry. However, in other studies, the validity of this model was partially supported. Hagemann and colleagues [29] examined the relation between resting EEG alpha asymmetry and personality traits of PA and NA, neuroticism (N), and extraversion (E). In this study a significant association was highlighted between the right hemisphere activation and NA trait, but no significant association was found between alpha rhythm and PA trait. However, these authors reported, in contrast with the emotional model, a left anterior temporal activation in subjects with higher NA scores, while they did not find any significant association between NA and N or PA and E. These results suggested that the biological bases of N and NA are different [29], disconfirming the hypotheses of Eysenck and Eysenck [168], according to which N trait should be positively associated with negative affect, whereas E trait is positively associated with positive affect. Minnix and Kline [36], in contrast with Hagemann and colleagues [29], observed that higher N or emotional lability levels were associated with greater variability of mid frontal asymmetry. These authors proposed the inconsistency of the outlined relationship between neuroticism and right frontal activation, and suggested the necessity to provide a novel neurobiological index sensitive to individual differences in N and able to predict psychopathologies linked to this trait. In general, a left hemisphere hypoactivation in anterior regions is a biological marker of affective style and related to the risk of psychopathology [27]. To assess whether | 3,069,325 | 225113911 | 0 | 16 |
resting anterior asymmetry discriminates individual differences in repressive coping styles, Tomarken and Davidson [27], in a sample of university students, studied the relationship between defensiveness copying style and EEG alpha asymmetry. In their experiment the authors administered the Marlowe-Crowne Social Desirability Scale [77] and the State-Trait Anxiety Inventory [78], before recording the EEG in resting condition. Defensiveness trait was associated with greater right frontal activation in the presence of an opposite-sex experimenter, but not with a same-sex one. In other EEG alpha asymmetry studies, in the presence of opposite-sex experimenters, but not same-sex experimenters, high-defensive participants had a relative frontal left hemisphere activation, while, low-defensive participants had a frontal right hemisphere activation [30,169]. Further, in another study, the defensiveness trait resulted in being related to the retrospective quality of parental caring [170], suggesting that repressed coping style, or defensiveness trait, and perceived maternal caring predicted left lateral frontal alpha activation [30]. According to other authors, frontal EEG asymmetry reflects not only emotion, but also individual differences in motivational personality traits [171,172]. In their pioneer experiment, Sutton and Davidson [28] showed that EEG alpha asymmetry explained more than 25% of the variance in the self-report measure of BAS and BIS traits, but prefrontal EEG asymmetry, however, was not significantly correlated with PA or NA. This research demonstrated that resting EEG alpha asymmetry can be predicted by BIS and BAS motivational traits. In this study, participants with greater prefrontal left hemisphere activation reported higher levels of BAS, whereas those with greater prefrontal right hemisphere activation reported higher levels | 3,069,326 | 225113911 | 0 | 16 |
of BIS. In this vein, the approach/withdrawal, or motivational model, of frontal EEG alpha asymmetry highlights that frontal brain activity corresponds to motivational propensities to approach versus withdraw behavioral tendencies [120,122]. Later, Coan and Allen [33], in an attempt to replicate Sutton and Davidson's findings [28], reported that approach motivation was a valid construct associated with EEG asymmetry findings in the temperament, emotion, and psychopathological domains, but, in contrast with the prediction of the model, the right hemisphere asymmetry in higher BIS scorers was partially confirmed. Although Sutton and Davidson [28] argued that higher BIS scores were related to a greater right frontal activity, Coan and Allen [33] found only a weakly significant relationship between BIS and right hemisphere activation in the mid frontal region rather the frontal region. Probably, in this study, the discrepancy was due to the different conceptualization of withdrawal and BIS constructs used in the two studies. Davidson [120] conceptualized a withdrawal construct as the system that motivates, or potentially motivates, organisms to withdraw from sources of aversive stimulation, whereas Gray [173] conceptualized the BIS as the system that, among other things, interrupts ongoing behavior, increases arousal, and increases attention, none of which inevitably leads to a withdrawal response. Hewig and colleagues [37] suggested that the problem of replicability could be due to the different conceptualization among the withdrawal and approach systems that could both be subsystems of the behavioral activation system. Authors proposed a new view of the approach/withdrawal model of anterior asymmetry, in which the behavioral activation system is related | 3,069,327 | 225113911 | 0 | 16 |
to bilateral frontal cortical activity, and right and left activations related, respectively, to withdrawal and approach behavior [174]. This model is in line with results of Harmon-Jones and Allen [175], who reported a positive relation among bilateral frontal cortical activity and BAS. In this vein, behavioral activation is the product of both approach and withdrawal motivational traits [37]. Research on personality correlates of right frontal alpha asymmetry has demonstrated that a higher dispositional tendency to experience withdrawal-related behaviors was related to increased proneness to nostalgia or sadness [62]. Adolph and Margraf [63] studied the relationship among symptoms of anxiety, depression, and frontal asymmetry in a sample of healthy individuals. Results indicate that higher symptom severity of depression and anxiety were correlated to a larger right frontal cortical activity. Furthermore, a larger right frontal cortical activity was influenced by anxiety symptoms [63]. In sum, frontal alpha asymmetry can be considered a biological marker for the risk of anxiety and depression [3]. From a genetic point of view, research affirmed that the relation between frontal alpha asymmetry and the risk for anxiety and depression is heritable only in young adults (males 32% and females 37%), but not in middle-aged adults [40]. In particular, the BDNF Val 66 Met polymorphism would be associated with the depression trait and mediated by EEG alpha power [42]. These findings highlight the utility of studying the relation among EEG measures and genotype to elucidate the pathway that elapses between the expression of an endophenotype and individual dispositions in personality traits [42]. According to | 3,069,328 | 225113911 | 0 | 16 |
Mathersul and colleagues [44], increased activity of alpha rhythm in the right parietal-temporal cortex is related to higher comorbidity of anxiety and depression, while increased right parietal-temporal alpha activity is related to anxious apprehension. These data support predictions for frontal, but not posterior regions and are in line with the motivational model of Davidson [120], in which depressed individuals differ from controls by an increase in withdrawal trait and negative affective valence, but in contrast to the valence-arousal model [176]. According to Heller [176], depressed mood is characterized by an asymmetrical profile associated with increased right frontal activity, due to a dissociation among lower and higher right parietal-temporal activity. Moreover, in this experiment, individuals that used a higher coping style oriented toward an emotional approach (through emotional expressions), had neural activities indicative of greater approach motivation [44]. Positive emotional expression traits are significantly related to greater left-sided frontal alpha asymmetry in the resting EEG condition [46]. According to Zhang and colleagues [71], participants who showed a higher relative left frontal activity during a resting state condition, exhibited fewer difficulties in everyday emotion regulation, especially in the dimension of impulsive control. Among personality traits related to impulsive control, the positive urgency (defined by Cyders and colleagues [108] as the tendency towards rash action in response to extreme positive emotional states) is related to left frontal alpha asymmetry. Gable and colleagues [59] found that higher levels of positive urgency trait were associated with a greater left frontal EEG activity, which originates from reduced right frontal activity in the | 3,069,329 | 225113911 | 0 | 16 |
inferior frontal gyrus [59]. According to these authors, a decreased right frontal activity could be considered as a potential neurobiological trait of impulsivity, related to the higher activity of the supervisory control system. This result was later confirmed by Neal and Gable [64], who suggested that impulsivity is related to reduced right frontal brain activity. Furthermore, higher BIS levels were related to greater right frontal activity, while BAS and FFFS traits (motivation to approach and motivation to withdrawal, respectively) were not associated with frontal alpha asymmetry. The authors state that regulatory control processes are associated with BIS and impulsivity and related to the right frontal activity rather than to withdrawal motivation expressed by the FFFS [64]. Another personality trait associated with impulsive control and the predisposition to approach is sensation seeking [177]. In two studies conducted in separated laboratories with different samples, Santesso and colleagues [45] examined whether the pattern of left frontal resting EEG activity related to approach-related behaviors and sensation seeking. Both studies highlighted that sensation seeking is associated with a greater left frontal alpha asymmetry in resting EEG, specifically in male participants. These authors suggested that this pattern could reflect the predisposition of sensation seekers to search out novelty stimulus or engage in risky behaviors to reach the reward. Concerning the parallel dispositional measures within the framework of the behavioral approach construct, De Pascalis, Cozzuto, Caprara, and Alessandri [57] observed that both dispositional optimism and BAS traits are related to EEG alpha asymmetry. In this study, findings on power spectral density in the | 3,069,330 | 225113911 | 0 | 16 |
alpha band have shown a robust relationship between higher cortical activity in the left middle frontal gyrus (BA11) and BAS. Optimism was related to both anterior left frontal cortical activation in the superior frontal gyrus (BA10), and a higher right-sided cortical activation in the posterior cingulate (BA31). In particular, alpha asymmetry in the posterior cingulate cortex, BA23 and BA31 regions, was uniquely associated with positivity trait, a basic disposition necessary to integrate self-referential thought and autobiographical memories [58]. In this vein, approach behavioral trait would be associated with greater left frontal activity, while behavioral avoidance trait would be associated with the greater right frontal alpha activity [59]. However, several findings do not support the relationship between motivational theory [120] and frontal alpha asymmetry. For example, another recent study conducted by Wacker and colleague [51], did not support the predicted left frontal asymmetry relation with the trait BAS/agentic extraversion (BAS/AE), but a positive relationship among consciousness (C) and frontal alpha asymmetry was observed [51]. Furthermore, within the frame of the Big Five theory [94], it was found that the personality traits of the NEO-Five-Factor Inventory (NEO-FFI) were related to alpha-beta coupling only in male participants [38]. Mainly, men with extreme trait levels differed in slow brain alpha activity compared to women [39]. However, according to Korjus and colleagues [61], the five dimensions of NEO-FFI personality traits, as well as their subordinate measures, could not be predicted from the resting state EEG data. At a neurobiological level, Pavlenko and colleagues [47] hypothesized that a well-developed alpha rhythm is | 3,069,331 | 225113911 | 0 | 16 |
characterized by an active and stable functioning of the cerebral dopaminergic system since they found that this pattern simultaneously serves as a prerequisite of high emotional stability and social adaptability. These findings are in line with the evolutionary assumption of Knyazev and Slobodskaya [34], suggesting that alpha rhythm reflects the adequacy of descending inhibitory control generated by the thalamocortical system, associated with cognitive performance [47]. Further, Razoumnikova's [35] findings indicate that, in male participants, higher levels of cognitive performance would be related to enhanced cortical connectivity of fast-frequency alpha rhythm [35]. Emotional intelligence is another trait related to cognitive abilities [178] and motivational neurobiology [130]. In terms of EEG frequency oscillations and individual differences, higher levels of emotional intelligence were associated with higher levels of positive affect and lower levels of negative affect [179], and positively related to a frontal left-sided alpha EEG asymmetry [50,180]. In conclusion, the present research review examined the relationship between interhemispheric EEG asymmetry and personality traits. In this context, alpha activity, in resting condition, has been the most used to derive an index of hemispheric asymmetry. Thus, this brain oscillatory activity was the most discussed in this review. However, this does not mean that alpha rhythm has produced the most stable and reliable results. Unfortunately, the study of this relationship provides controversial and unclear results. Several studies have supported the motivational model [28,[43][44][45]57,59,62,63,71], many others have supported it partially [59,64,67], and others have disconfirmed it [29,33,37,52,64,66,175]. Interactional and Contextual Variables in the Relationship between Personality Traits and EEG Alpha Asymmetry Recent | 3,069,332 | 225113911 | 0 | 16 |
research has studied the influence of interactional and contextual variables in the relationship between interhemispheric EEG asymmetry and personality traits. In particular, contextual variables, such as time of day and season [48], mood state and pre-and post-cap preparation [32], and experimenter sex [31,66], can influence the relation among EEG alpha asymmetry and personality traits. To demonstrate that a relationship is reliable, multiple recording sessions should be necessary, because only half of the variance in a resting session is due to the trait influences [25]. In this framework, Peterson and Harmon-Jones [48] studied, in two different samples, the role of different seasons and time of day in the relation of resting EEG alpha asymmetry and personality traits of approach-avoidance, nurturance, and dominance. In the first experiment, the EEG baseline of participants was recorded before noon and in the afternoon, both in the spring and summer months, and in the autumn and winter months. Results highlighted that frontal alpha asymmetry in resting EEG reflects circadian and seasonal influences. The right frontal activity increased during autumn mornings. These results could explain why the relation between resting alpha asymmetry and personality traits is not replicable across studies [181]. With regard to the influence of experimental context on EEG performance, Blackhart and colleagues [32] assessed that EEG cap preparation leads to a less positive mood. In this experiment, the measures of mood (evaluated with the self-assessment manikin) most proximate to the EEG recordings were associated with asymmetry when the results of pre-cap preparation mood ratings were statistically controlled. Men and women | 3,069,333 | 225113911 | 0 | 16 |
showed a shift toward a more negative mood state post-preparation. Negative mood post-preparation, but not pre-preparation, predicted relative left frontal activation in women. For women participants, another important intervening variable to consider before the EEG recording measures is the menstrual cycle. In particular, higher levels of neuroticism (a parallel measure of BIS) were related to lower left prefrontal activity than lower levels during the mid-late luteal phase of the woman. This relation was identified as indexed by slow alpha component, and alpha-total asymmetry scores in the prefrontal regions. Therefore, the relation among resting frontal alpha asymmetry and high/low neuroticism levels in females is moderated by the menstrual cycle [60]. Finally, in a recent study, conducted by De Pascalis, Sommer, and Scacchia [66], on a sample of right-handed female university students, the authors discussed the relevance of taking into account the gender of experimenter. In this experiment, the authors examined the association among Reinforcement Sensitivity Theory-Personality Questionnaire (RST-PQ) traits [89] and alpha asymmetry in resting EEG. Results indicate that in the total group, which included two subgroups with experimenters of different gender (male, female), FFFS was related to the greater left rather than right frontal activity, while BIS was related to the greater right frontocentral activity. These associations remained significant for the subgroup with a young same-sex experimenter, but not with an opposite-sex experimenter. In conclusion, it can be affirmed that besides the different conceptualization models, the interactional and contextual variables can also lead to a lack of replicability of the results in relation to EEG alpha | 3,069,334 | 225113911 | 0 | 16 |
rhythm and approach/avoidance personality traits. Approach/Avoidance Personality Traits and EEG Theta Rhythm The theta rhythm is a slow brain activity within a typical frequency range of 4-7 Hz [182]. According to Kramis, Vanderwolf, and Land [183], this rhythm is classified as type 1 theta (8 Hz), associated with locomotion and voluntary behavior, and type 2 theta (4-7 Hz), associated with motionlessness. The main brain dipoles that generate theta rhythm are sited in the midline prefrontal region of the cortex [184], the hippocampus, and the limbic system [185]. Theta oscillations are involved in various cognitive abilities, such as associative thinking [186], the encoding of information, active exploratory movements, spatial navigation of the environment, and memory [187]. In a study, Razoumnikova [35], in a sample of adult males, studied the relationships among EEG power and coherence measures of brain oscillations, and personality traits of extraversion, neuroticism, psychoticism, sensation-intuition, thinking-feeling, judging-perceiving, and emotional intelligence. Results showed that higher levels of emotional intelligence were characterized by an increase in theta power in the right hemisphere, while lower levels of this trait were related to increase in theta power in the left hemisphere. In the subgroup with high levels of emotional intelligence, as compared to the subgroups with low levels, there were lower levels of power of type 1 and 2 theta-bands, and slow alpha bands, while there were greater levels of power in the beta-band. Furthermore, the groups with high emotional ability, compared to low groups, were related to higher interhemispheric coherence. According to the author, the results highlighted that | 3,069,335 | 225113911 | 0 | 16 |
EEG spectral parameters, in resting EEG conditions, reflect the relationships between neuronal integration (memory) and personality/intelligence variables. With regard to the primary personality traits, several studies suggest that the posterior-anterior distribution of resting EEG activity [37,175,188], in the delta and theta frequency range rather than alpha range [51,52,54], is associated with the extraversion personality trait. In line with this evidence, Chavanon, Wacker, and Stemmler [53] observed an association among agentic extraversion (AE), and posterior versus anterior resting EEG theta activity in the rostral anterior cingulate cortex. According to Knyazev,Bocharov,and Pylkova [56], AE trait is related to higher theta activity in the posterior default mode network and lower theta activity in the orbitofrontal cortex. These results suggest higher tonic activity in the orbitofrontal cortex and lower activity in the default mode network in extraverts compared to introvert participants. In sum, from among the four articles included in this section [35,53,55,56], it emerges that emotional intelligence [35] and personality traits modulate the activity of theta EEG activity [55]. In particular, for AE it was highlighted that rostral anterior cingulate activity generates posterior versus anterior theta activity [53]. On this basis, it has been suggested that frontal-posterior EEG theta spectral power gradient can be considered as a marker of extraversion personality trait [56]. Approach/Avoidance Personality Traits and EEG Delta Rhythm Delta rhythm is a slow brain activity within a frequency range of around 0.5-3 Hz, associated with regenerative processes such as deep dreamless and sleep [189]. In particular, delta activity is supposed to reflect cortical reorganization of waking circuits | 3,069,336 | 225113911 | 0 | 16 |
and it is related to the activity of the parasympathetic nervous system, and the activation of ascending cholinergic projections from the thalamus [190]. According to Knyazev [164], although the origin of delta rhythm is uncertain, the dipole generators of these oscillations are located in the anterior medial frontal cortex [191], the subcortical regions linked to the brainstem [192], the nucleus accumbens [193], and the ventral tegmental area [194]. These brain regions are associated with dopaminergic activity and the approach/avoidance motivational traits [195]. Within an evolutionary framework of the brain oscillation systems, Knyazev and Slobodskaya [34] evaluated the relationship between resting-state EEG of adult right-handed male and female university students and BIS trait (Gray-Wilson Personality Questionnaire [88]). The strength of descending noradrenergic fibres of the locus coeruleus [196] was measured by the negative correlations among delta, theta, and alpha powers, separately estimated in each EEG band [2]. Their results confirm that higher BIS scores were associated with the enhanced negative coupling alpha to the delta frequency oscillations. These results were confirmed in other research in which increased levels of delta beta coupling were associated with state anxiety [49], indicating a predominantly cortical origin of the trait anxiety. Furthermore, higher levels of state anxiety increased the alpha-delta anticorrelation and were positively related to the power of alpha oscillations, and negatively related to the power of delta oscillations [34]. In terms of anxiety trait, Eysenck [197] explained neuroticism as the product of activation of the sympathetic nervous system, so that higher scores in neuroticism (N) are positively related with | 3,069,337 | 225113911 | 0 | 16 |
greater activation levels, i.e., lower activation thresholds, within this subcortical structure. Tran and colleagues [38] investigated the relationship among individual personality differences [94] and eyes-closed EEG resting brain activity. The authors suggested that there is a significative effect of gender on N trait-women exhibited higher levels of anxiety trait than men, while, extraversion (E) and consciousness (C) traits were associated with delta and theta rhythms in all cortical regions. Generally, NEO-FFI personality traits were associated with the amplitude of alpha and beta oscillations in men [38]. The approach/avoidance personality traits and EEG activity in the delta range were also found associated with reward and stimulus salience processing in the reward circuit [164]. In a recent research, De Pascalis, Vecchio and Cirillo [69] tested whether cortical-subcortical coupling would increase as a function of decreased delta (theta) or higher beta (gamma) activity in a sample of right-handed university students during a resting anxiogenic situation and a relaxation situation. To evaluate the influence of state anxiety and approach/avoidance personality traits on these neurobiological processes, participants completed the State Anxiety Inventory [198] and the Reinforcement Sensitivity Theory Personality Questionnaire [89]. During the resting anxiety condition, a significant positive between-subject delta-beta correlation was observed. This association was significantly higher than the association observed during the relaxation condition. In the anxiety, but not in the relaxation group, a delta-beta coupling for the low delta activity was observed. In addition, in the anxiety condition, BIS was significantly associated with a higher strength of within-subject delta-beta coupling, while, in the relaxation group, BIS was | 3,069,338 | 225113911 | 0 | 16 |
positively associated with delta-theta coupling. In both groups, BAS goal-driven persistence sub-trait (BAS-GDP) was positively associated with higher delta-gamma coupling [69]. These results suggested that the coupling between slow and fast EEG frequency oscillations reflects cortical-subcortical interaction [164,199]. However, these findings should be interpreted with caution, because data findings relied on two separate samples of the university students and not on the general population. In terms of approach motivation behavior, the AE trait can be defined as the major expression of behavior and is associated with dopamine neural activity [200]. Wacker and Gatt [51] stated that resting posterior versus frontal EEG delta-theta activity is both sensitive to pharmacological manipulations of neural dopamine and associated with the AE. Furthermore, posterior versus frontal resting EEG delta/theta activity represents the molecular genetic basis of agentic extraversion associated with Catechol-O-methyltransferase Val 158 Met (COMT VAL/MET) polymorphism [52], and is sensitive to dopamine D2 receptor antagonist-induced changes in dopaminergic activity [54]. Studying the relationship among the posterior-frontal distribution of slow oscillations, Koehler and colleagues [54] confirmed Depue's and Collins' statement that agentic extraversion is linked to individual differences in dopaminergic activity, although these authors did not emphasize a significant association among extraversion and DRD2. In sum, the eight studies reviewed and analyzed in this section have demonstrated that the psychological traits of personality modulate the activity of delta as well as theta EEG activity [55]. In terms of the BAS/E trait, some of these studies highlighted that this trait was related to delta-theta coupling at posterior versus frontal brain regions [51,54]. | 3,069,339 | 225113911 | 0 | 16 |
Interesting, BAS-GDP was positively related to higher delta-gamma coupling [69]. Using the NEO-FFI, Tran and colleagues [38] found that delta-theta activity was related to E and C, while the alpha-beta coupling was related to personality traits in males only. In terms of BIS/N, higher delta-alpha coupling has been related to increased behavioral inhibition [34], while the increased delta-beta coupling is associated with state anxiety [49]. Finally, the BIS trait was related to higher delta-beta coupling during a state of resting anxiety and with higher delta-theta coupling during a neutral resting condition [69]. These results disconfirmed the frontal alpha asymmetry hypotheses for the BAS trait [52]. Findings from the above-mentioned studies suggest that the evaluation of coupling among slow and fast rhythms is a good method for evaluating cortical-subcortical excitability in behavioral processes. Discussion This review mainly aimed at studying the relationship among resting EEG cortical activity in resting condition, and individual differences in approach/avoidance motivation personality traits. Another aim was to understand which EEG frequency oscillation and the associated scalp-distributed lateral asymmetries can be defined as an index of cortical excitability sensitive to the approach/avoidance motivational personality traits. Research on databases has shown that many studies have satisfied the inclusion criteria, confirming the high interest of the researchers on this topic. This interest was opened to many factors, such as the study of the neurobiological underpinning of behavioral individual differences [26][27][28][29], the validation of the motivational personality theory [8,33,46,52,56,57,59,64,67], and the investigation of the neurobiological cortical markers related to the risk of psychopathological disease such as | 3,069,340 | 225113911 | 0 | 16 |
anxiety and depression [30,31,37,41,43,44,62,63], or behavioral disinhibition [45,64,71]. In accordance with the motivational model theory [121], research showed that the EEG gamma frequency oscillation, or the associated scalp-distributed lateral asymmetries, is not a good index of approach/avoidance motivation personality traits. Interesting results were found from the study of resting-EEG beta-band activity and approach/avoidance personality traits, wherein the results highlighted that resting beta asymmetry is a neurophysiological marker of approach/avoidance personality traits [8,67]. With regard to the study of EEG alpha asymmetry and the affective/motivational dispositions, some research has supported the motivational model theory [28,44,45,57,59,62], others have partially supported it [5,33,43,64,66,71], or disconfirmed it [29,37,52,176]. A number of studies on the relationship between brain oscillations and personality have outlined that frontal-posterior EEG theta spectral power gradient is a good index of cortical excitability in the approach/avoidance motivational personality traits [51,53,54], and a stable individual measure related to extraversion personality trait [56]. Regarding to the BIS functions, higher delta-alpha coupling is related to increased behavioral inhibition [34], while an increased delta-beta coupling is associated with state anxiety [49]. In sum, all these findings indicate that the coupling among fast and slow rhythms can be considered as indexes of cortical-subcortical interactive influences on personality traits [69]. However, the current review suggests that these results should be interpreted with caution, because several methodological problems persist in this field of research. The qualitative assessment of the selected articles emphasized a medium risk of bias (see, the last column" Total" in Figure 2). This result could depend on several factors. Many researchers | 3,069,341 | 225113911 | 0 | 16 |
did not conduct any evaluation referring to the anamnesis of the participants enrolled in their research. They did not consider the possible influence of organic, psychological, psychopathological, neurological disorder, or brain trauma, and the eventual intake of drugs or psychostimulants before the resting-EEG recording was done [26,27,[29][30][31][32][33][34][35][36][37][38][39][40]45,[47][48][49][50]52,[54][55][56][59][60][61][62]64,65,67]. Further, although in some studies researchers have evaluated the history of diseases and the eventual use of drugs, they did not control for the limitation of the assumption of psychotropic substance intake, like caffeine or nicotine, two hours before the rest-EEG recording [18,28,39,68,70]. It is known that the taking of drugs or psychotropic substances by the participant may impair the brain activity during resting-EEG recording [201,202], and that also, the presence of an organic or neuropsychological disease [203] may alter the brain rhythms of the participants, confounding the validity of the results obtained. Moreover, many authors did not take into consideration the handedness of the participants in the relationship studied [33][34][35]38,39,41,42,[47][48][49][50][51][53][54][55]61,62,65,70,71]. Although some authors did not consider this factor as relevant [40], we think it is important to do so [72,73]. From a methodological point of view, the studies selected had not always adopted adequate criteria for EEG measurement, nor for counterbalancing the order of the opened-/closed-eye sequences of EEG recordings [31,36,41,42,[44][45][46][47][49][50][51]62], or these data were not clearly reported [28,30,32,39,[56][57][58]64,[69][70][71]. For example, in the study by Konareva, a counterbalancing between the eye conditions was not adopted [55], while Korjus and colleagues [61] generalized their results obtained from five resting-state experiments conducted using different samples and different recording times (i.e., | 3,069,342 | 225113911 | 0 | 16 |
1 min, 2 min, and three separate sessions of 1 min, respectively). In particular, in these studies, the method used produced several limitations regarding the validity and reliability of the significant relations obtained. Additionally, the use of counterbalance strategies is necessary to reduce the order effect and the sequence effect, which increases the validity of the EEG measures. In addition to the appropriate reference electrode placement and the length of EEG recording, there are other important factors to consider for reliable asymmetry or frequency oscillation measures. According to Hagemann [25], the good reliability of the asymmetry measure in a resting-state can only be achieved if the EEG is recorded for at least 4 min. However, in some reviewed studies, many researchers conducted EEG recordings for less than 4 min [30][31][32]36,40,43,49,56,65,69], others for 2 min [42,44,47,51,57,58,60] and, finally, some for 2 min or less [45,71]. Moreover, some other researchers used short recording segments, such as 15 [60] or 30 s [62,71]. Although some studies showed that alpha power at single sites shows good reliability estimates for EEG segments as short as 20 or 30 s [204,205], this observation may not be generalizable to other asymmetry measures obtained for other brain oscillations [25]. This could produce a lack of relation between brain rhythms and personality traits that would otherwise be significant in longer EEG recording segments. The method used for EEG recordings in eyes-open and eyes-closed conditions should be carefully reconsidered. Many researchers have recorded resting-EEG by asking the participants to refrain from blinking and/or moving their eyes | 3,069,343 | 225113911 | 0 | 16 |
by fixating on a cross to minimize ocular artefacts [51,57,58,61,66], or they did resting-EEG recordings in an eyes-closed condition [35,40,42,54,68]. In the first case, the method is confounding, because blinks and spontaneous eye movements are controlled by several autonomic brain systems [206], and the instruction to suppress these systems may act as a secondary task [207], while in the second case, to study the brain activity only in a closed-eyes state leads to a poor external validity of the EEG measures obtained. Further, the use of different reference schemes is also another important factor to consider in EEG asymmetry research. In the studies selected, different EEG reference schemes were used, such as the average to overall electrodes [43][44][45]54,67], the reference to average voltage [8], the link to an active electrode [47], or the link to the left earlobe [46,48,59,71], but among these, the average over two electrodes positioned on the earlobes or mastoids [28,[30][31][32][34][35][36][38][39][40][41][42][43][49][50][51]56,60,61,65,69], and the reference electrode positioned in the middle of the scalp between Fz and Cz sites [54], FCz site [70], or on the Cz site [26,27,29,37,45,52,57,58] were the most commonly used. These differences undermine the generalizability of the findings. However, despite the fact that many researchers were using the Cz electrode, positioned in the middle of the scalp as a reference, this could lead to numerous problems regarding the validity of the EEG measurement. According to Hagemann [208], the vertex reference at Cz has an unfavorable signal-to-noise ratio, because Cz is an active electrical site, and depending on the amplitude and phase | 3,069,344 | 225113911 | 0 | 16 |
relations between the two target sites and the reference site, the true amplitude asymmetry of the target sites may be enhanced, mitigated, or even reverted. Moreover, the same considerations are true to any other active electrode used as a reference scheme for the EEG measurement. For this reason, the linked earlobes/mastoids reference scheme would seem the better solution to this problem-the average of A1 and A2 is substantially less active than the cephalic target sites [25]. However, although this scheme has been repeatedly indicated and considered as the best solution in this EEG research field [25,208], today still no consensus has been reached among researchers. Another solution, as suggested by Coan and Allen [33], could be to use a general linear model of analysis, which allows the inclusion of a repeated measures factor by considering as factor the reference schemes used for EEG recordings. The relationship between brain activity and approach/avoidance behavioral traits could be moderated not only by the EEG reference schemes, but also by the interactional or contextual variables (e.g., participant's mood, sex of experimenter, or time of day and time of year in which the EEG is recorded). Two studies have reported that time of day and time of year are correlated with alpha asymmetric frontal cortical activity (studies 1 and 2 [48]), revealing that the right frontal activity is highest during autumn mornings. These results had important health implications and suggested the EEG as an endophenotype of the risk of depression. Research has argued that the time of year is associated with | 3,069,345 | 225113911 | 0 | 16 |
an increased depression state [209], the time of day is associated with higher cortisol levels [210], and the cortisol level has been linked with withdrawal motivation. Thus, a greater relative right frontal activity at rest in the autumn mornings could be due to the combination of variables associated with a decreased approach motivation and increased withdrawal motivation [5]. Several studies have suggested that controlling the mood before EEG recordings might increase the predictive value of the studied relationship, because the procedure of fitting an EEG cap, such as the abrasion of the scalp, and the application of gel during the EEG preparation, is aversive and, thus, may induce a negative affective state or avoidance. Therefore, differences in transient mood may contribute to the state variance of resting asymmetry [32]. Perhaps another factor that contributes to the state variance of resting asymmetry is a transient state of approach and withdrawal motivation. Higher motivation to approach may respond to the novel lab situation with greater relative left frontal activity, whereas individuals with higher withdrawal and motivation to inhibition may respond to the novel lab situation with greater right frontal activation [5,66]. Therefore, it is very important to consider the influence of interactional and contextual variables that can confound the relationship between EEG activity and motivational personality traits. This influence can be reduced by conducting multiple EEG recordings [3]. However, among the studies reviewed, only a few have evaluated the construct validity of EEG measurements in multiple recording sessions with a total of three EEG measurements 3 weeks apart | 3,069,346 | 225113911 | 0 | 16 |
[26][27][28]37,43,60], and only one study analyzed the stability of the relation, over a long time of retest, for a total of three EEG measurements 1 year apart (study 3 [52]). Thus, it is to be assumed that the construct validity of the studies included in this review is poor. The measures conducted in multiple EEG sessions across time can constitute better reliability and construct validity of the measured relation [25,27]. Finally, in terms of the quality assessment of the studies included in this review (Figure 1), we think that the statistical analysis was adequate to the studied outcome. The studies used valid and reliable methods to evaluate the influence of the brain cortical activity on the individual disposition of approach/avoidance personality domains, including appropriate analysis for the used sample size and adequate control for the confounding variables considered by the authors. However, some studies used statistical models without considering the role of education [44,52], gender [18,28,30,33,36,37,41,47,48,50,51,55,59,62,68], and age [38,42,54,68], in the relation studied. Gender and age can modulate the relationship between brain activity and motivational traits of personality. In the studies by Santesso and colleagues [45], for example, the authors highlighted that higher sensation-seeking levels were related to a greater left frontal activity at rest in male participants only, while other studies have observed higher neuroticism levels in women than in men. In particular, Huang and colleagues [60] demonstrated that the menstrual cycle is an interactional variable that can alter the resting frontal alpha asymmetry. Unfortunately, only five articles selected in this review considered the influence | 3,069,347 | 225113911 | 0 | 16 |
of the menstrual cycle in personality traits as an interactional variable [57,58,60,66,69]. In terms of age influence, results appear to be more consistent. However, some studies evaluating the role of age on the frontal asymmetry heritability, found that frontal-alpha asymmetry is heritable only in young adults, but not in middle-aged adults [40]. Although we checked for the method used in the reviewed studies, this work presents some limitations that could undermine the generalizability of the findings. The first limitation is related to the heterogeneity of samples and methods used for the EEG measurements. The second is due to the heterogeneity of the EEG phenomena studied (asymmetry, and/or brain rhythms), which have determined a lack of a quantitative analysis in the meta-analysis. This would have given a greater strength to the inferences by examining the size of the effects studied. Another limitation is related to the choice to include only academic articles published in peer-review journals. This aspect could have limited the selection of only those studies that have obtained results in line with the literature, and consequently have influenced the publication bias. Therefore, the presented results could have an overestimation of the relationship observed. In addition, the choice to select only the studies published in English and in Italian could have led to the deletion of studies conducted in other populations. In conclusion, it can be assumed that research on the relationship of resting EEG cortical activity in idling condition and the approach/withdrawal motivational model has provided controversial and unclear results. Findings have shown that gamma, | 3,069,348 | 225113911 | 0 | 16 |
delta, and alpha frequencies are not good indicators of cortical excitability that can be associated with approach/avoidance motivation personality traits, and although in some studies beta and theta frequencies have resulted as good markers of approach/avoidance motivational behavior, the number of studies is scarce. Finally, to confirm these promising but "preliminary" results, and to give greater validity, future research should consider the role of gender contextual interactional variables, discussed above, in these relations, and conducting multiple sessions of resting-EEG recording. Conclusions Observations derived from this review are in accordance with Harmon-Jones and Gable's [5] considerations that the manifestation of trait frontal asymmetry is until today an unknown phenomenon, as well as the association of scalp-distributed lateral asymmetries with approach/avoidance motivation personality traits. Although the reliability of resting EEG measures in idling condition is hypothetically comparable with the reliability of self-reported personality traits and can be used as a valid signature of a person, the trait frontal asymmetry could simply reflect individual differences of frontal asymmetry in an idling rest condition [6]. This endophenotype can be, in fact, influenced by situational and interactional variables related to the experimental contest, such as the psychological state of the individual, and the unconsciously cognitive processes performed by the participant during the resting EEG recording, which are impossible to control [211]. Besides, it is necessary to remember that the study of electrocortical correlates should be interpreted with the utmost caution, because genetic factors [51,54], hereditary [33,40,42], and situational factors [212] can all interact to modify behavior and brain dynamics, and expressions | 3,069,349 | 225113911 | 0 | 16 |
of personality traits [213]. Conflicts of Interest: The authors declare no conflict of interest. | 3,069,350 | 225113911 | 0 | 16 |
Research on heat transfer enhancement of variable cross sectional conformal cooling of injection mold based on fluent The purpose of this paper is to present a technique of variable cross section conformal cooling channels (VCCC) to compare the cooling effect of moulds with equal section channel experimentally. The influence of the size structure parameters of the variable cross section conformal cooling channel on heat transfer is studied. It is found that the ratio of D/d=1.4 has the best effect of enhanced heat transfer. To determine the better heat transfer effect of variable cross section channel,this paper studies the influence of variable cross section channel and traditional equal section channel on heat transfer and takes temperature distribution, pressure drop and water velocity as evaluation indexes. In addition, in order to further discuss the effect of the conformal cooling channel structure, the influence of the opposite direction channel arrangement and the same direction arrangement on the heat transfer is studied. It is found that the adjacent channel of the opposite direction arrangement has better heat transfer effect and cooling uniformity. INTRODUCTION During the injection molding process, the melt plastic injected into the mold cavity is rapidly cooled from 200 ~ 300 to 60 ~ 80°C in mould opening stage, and about 95% of the heat released by the cooling is taken away by the fluid medium (Ilyas et al., 2010).The cooling system controls the temperature change of the mold and the distribution of the temperature field.The temperature of the mold directly affects the smoothness of the molding process.The | 3,069,351 | 139117299 | 0 | 16 |
temperature field distribution at different times is related to the surface quality and dimensional accuracy of the final product.This is the main thing that affects the physical and mechanical properties of the product.In addition, the speed of temperature changes also affects the molding process of energy consumption and product molding cycle.Therefore, the cooling system research has been one of the key areas of injection molding. In order to solve the problem of uniform cooling, the researchers proposed the conformal cooling water channel.Conformal cooling water channel refers to the *Corresponding author.E-mail: [email protected]: 15002771087. Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License cooling water channel in which the injection cavity shape changes, and its mold cavity surface distance is always consistent.Wang et al. (2011) present an automatic method for designing conformal cooling circuits, which is an essential component that directly affects the quality and timing for products fabricated by rapid tooling.Nogueira et al. (2010) report in a case study involving the use of conformal cooling channels obtained in wax by 3D-impression.Mohamed et al. (2013) present a simulation study of different types of cooling channels in an injection molded plastic part and compare the performance in terms of time to ejection temperature, shrinkage, temperature profile, and part warpage to determine which configuration is more appropriate to provide uniform cooling with minimum cycle time.Ilyas et al. (2010) present new results on the impact of conformal cooling on the productivity and energy efficiency of injection moulding, and on | 3,069,352 | 139117299 | 0 | 16 |
the durability of the indirect SLS material in injection moulding applications.A novel "cut-out volume" technique for powder clearing is also presented, along with a set of design rules to support further application of the work.Marques et al. (2015) proposed two conformal cooling designs: i) parallel circuit; ii) serial circuit. In order to understand the cooling effect of different cascading cooling solutions using the geometry of the plastic part as a workpiece, Wang et al. (2014) developed a new rapid die heating and cooling method and established a model to evaluate the effectiveness of the new rapid die heating and cooling method. This paper combines the characteristics of conformal cooling and enhanced heat transfer (Wang et al., 2011;Chen et al., 2014;Li and Liu, 2011;Xiao, 2006;Xue et al., 2011;Huang et al., 2005Huang et al., , 2006;;Zhang et al., 2008Zhang et al., , 2010)).The method of variable cross section reinforced heat transfer is proposed, and the water pressure drop, velocity and temperature field distribution of constantsection curve channel and variable cross-section curve channel are compared and analyzed by simulation software. Design of heat transfer enhancement of conformal channel An electronic plastic product is studied in this paper, as shown in Figure 1.The product shape is a surface structure with a thickness of 2.9 mm and the material is ABS.Its physical properties are shown in Table 1.The forming die in this paper adopts a mold and cavity. Equal section conformal cooling channel The traditional conformal cooling channel is equal section.And its layout is shown in Figure 2, according to the | 3,069,353 | 139117299 | 0 | 16 |
structural characteristics of the product and mold.The size parameters of the channel are shown in Table 2. Variable cross section conformal cooling channel The design of conformal cooling channel with the variable cross section can alleviate the problem of rising temperatures, uneven temperature distribution and residual thermal stress in the mold to a certain extent.The ratio of the best value range of the variable crosssection of the large diameter D and small diameter d is 1.1 to 1.7 (Lei and Yunxia, 2011).This paper selects three D/d ratio.In this paper, three kinds of D / d ratios are selected.The structural parameters of the variable cross-section channel are shown in Table 3, and the cross-sectional size of the cooling channel changes linearly along the flow direction.When D/d=1.2, its geometry is as shown in Figure 3; when D/d=1.4, its geometry is as shown in Figure 4; when D/d=1.6, its geometry is as shown in Figure 5. Grid independency In this paper, grid testing and final meshing are all conducted in Gambit, using Tet/Hybrid meshing.Taking one of the models as the grid test object, the inlet velocity u = 0.8 m/s, the inlet water temperature Ti = 298 K, and the outlet relative pressure P2 = 0 Pa are the test conditions.In this paper, we choose the average Nu reference and find out the suitable meshing method based on grid quality and unit number.The test results are as follows: Table 4 shows the grid quality and unit quantity statistics.Figure 6 shows the test grid chart.Figure 7 shows the line chart | 3,069,354 | 139117299 | 0 | 16 |
of the change of average Nu number with spacing. Outcomes analysis (1) In Table 4, as the cell size decreases, the number of cells and number of nodes increase sharply, while the The distance between the cooling channel The distance between the cooling channel and the cavity wall The diameter of the cooling channel 25 mm 25 mm 10 mm Structure of channel Parameter Value Diameter ratio D/d 1.2 1.4 1.6 Small diameter d(mm) 10 Large diameter D(mm) 12 14 16 average grid quality improves. (2) In Figure 6, as the unit spacing increases, the average number of Nu gradually decreases.After spacing = 1, the trend of change tends to gradually decrease and gradually balances. (3) From comprehensive consideration, the final cooling channel grid spacing is 1 mm, product grid spacing is 1.6 mm, and the mold grid spacing is 4 mm. Residual convergence A residual in numerical simulation is shown in Figure 8.The residuals of the variables involved in the iterative calculation are used as the basis for the numerical simulation to determine the convergence.It is plotted for continuity, x-velocity, y-velocity, z-velocity, Rayleigh kinetic energy (k) and Rayleigh dissipation factor (epsilon).The residual is in the order of 10-3; when the residual value is less than 10-3, the above reference is considered to converge and the residual energy control is in the order of 10-6. METHODS OF HEAT TRANSFER ENHANCEMENT SOLUTION The steps of solution In this paper, the simulated fluid is incompressible steady-state flow, and the separation solver is selected.The three-dimensional steady-state calculation is used.The | 3,069,355 | 139117299 | 0 | 16 |
operating environment is based on a standard environmental pressure, and the standard k-ε model is chosen without considering gravity.At the same time, the wall processing method for enhancing the wall function is adopted. The steps for fluent (Tan, 2002) to solve the problem are shown in Figure 9.The boundary conditions for solving the model are shown as follows: The inlet velocity of the inlet boundary condition is 0.5 to 1 m/s, and the water temperature is 25°C (2) The export boundary condition is set to the pressure outlet; (3) The wall surface of the channel and the mold wall are set to couple the wall condition, and the wall of the product and cavity are also arranged in a coupled wall condition. Heat transfer model The heat transfer model is shown in Equation 1. ) ( Where: The size of the surface heat transfer coefficient is related to many factors in the heat transfer process, including the physical properties of the fluid and the heat transfer surface size and layout, while the flow rate is closely related.In order to ensure uniform heat transfer from the cavity surface to the cooling channel, the Fourier heat transfer law was used to find the relationship between the inlet radius r and the exit radius R. According to the Fourier equation, the heat conduction rate of the radius r can be expressed as: Where, x is the length of the cooling channel, T0 (T0> T2> Ti) is the temperature of the cavity surface, and T1 is the temperature of the | 3,069,356 | 139117299 | 0 | 16 |
cooling channel near the inlet.The outlet heat transfer rate of radius R can be expressed as: Where, T2 is the temperature of the cooling water channel near the outlet.The thermal conductivity of the inlet and outlet of the variable cross-section cooling water is shown in Figure 10. In order to achieve a uniform heat transfer rate through the cooling waterway at any location on the cavity surface, the heat transfer rate q1 near the inlet must be the same as the outlet q2.The heat transfer and outlet heat conduction along the entrance of the cooling channel are constant: In Figure 11, the mathematical formula between the inlet radius and the exit radius of the variable cross-section channel can be found in Equations 5 to 7. Where d is the distance between the cooling waterway center and the cavity surface, To is the temperature of the mold surface, T1 is the temperature of the cooling water channel near the cooling water inlet, and T2 is the temperature of the cooling water channel near the cooling water outlet. Therefore, the size of the cooling channel radius R near the coolant outlet can be derived in Equation 8: Variable cross-section channel provides better cooling uniformity than conventional channel.By increasing the surface contact area near the outlet and increasing the volume of cooling water flow, it can take more heat from the plastic melt. In theory, the variable cross-section of the channel can compensate for the inlet-outlet coolant temperature difference by using a large radius of the cooling | 3,069,357 | 139117299 | 0 | 16 |
channel near the outlet and at the exit.In practice, variable cross-section channel can be designed and analyzed with CAD/CAM systems, and injection molds can be manufactured using fast tools or injection molds. Temperature field distribution of variable crosssection cooling products The temperature field distribution of the variable crosssection conformal cooling product is shown in Figure 12. From Figures 12 and 13, it can be seen that the temperature field distribution is basically uniform and the distribution is basically the same.In Figure 12a, the maximum local product temperature is 325 K, the average temperature is 313.5 K, the minimum temperature of plastic products is 302 K, the temperature difference is relatively small.In Figure 12b, it can be seen from the temperature cloud diagram that the maximum temperature of Figure b is lower than that of Figure a; the maximum temperature of the product is 321 K, the lowest temperature is 302 K, the higher temperature is distributed at the edge and the middle of the product.The temperature is 312.4K.The temperature in Figure 12c is significantly higher than that in Figure 12a and 12b.And the local maximum temperature of this product is 325 K; the lowest temperature is 304 K.The temperature difference between maximum temperature and the minimum temperature is relatively large, and the temperature difference is 11 K.In the product section shown in Figure 13, red parts represent the highest temperature in the temperature distribution profile.It can be seen that the temperatures shown in Figure 14a and c are significantly higher than that in Figure 14b.Therefore, we | 3,069,358 | 139117299 | 0 | 16 |
find that when D/d = 1.4, the hot cooling effect is the best. From the heat transfer formula, the heat transfer Q is positively correlated with the heat transfer area A and the surface heat transfer coefficient h.In the three structures mentioned above, the heat transfer area A increases as the diameter of the outlet increases.Therefore, in case where other conditions remain constant, the heat transfer Q also increases.The surface heat transfer coefficient h is positively correlated with the velocity of the water (Huang et al., 2005;Wang et al., 2014).When D/d = 1.2, a small heat transfer area and a higher flow rate lead to poor heat transfer.When D / d = 1.6, although the heat transfer area increases, the water flow rate decreases a lot, resulting in poor heat transfer effect.Considering these two reasons, we found that better heat transfer effects can be obtained when D/d= 1.4. Pressure drop distribution of variable cross-section conformal cooling products The pressure drop distribution of the product with variable cross-section conformal cooling is shown in Figure 15.It shown in Figure 14 that the maximum pressure drop of these three structures is reduced from 760 to 560 Pa.The flow of water from the inlet to the outlet end of the pressure is continuously reduced.The cooling water flows in the pipeline and the flow of water in the channel is affected by the channel structure.The speed of the fluid in the channel will also have a relatively large change.When the fluid flows in the tube, the pressure is reduced due to | 3,069,359 | 139117299 | 0 | 16 |
energy loss which is caused by the flow of fluid to overcome the internal friction and turbulence when the fluid particles collide with each other.The exchange of momentum is manifested in the fluid flow before and after the pressure difference, that is, pressure drop.The pressure difference is generated before and after the fluid flow.When the fluid flows through the channel, the boundary layer is constantly destroyed.So the heat transfer effect is enhanced.But at the same time, the pressure drop increases very quickly.Injection mold cooling channels of variable cross-section can significantly improve heat transfer enhancement effect. Variable cross section conformal cooling channel velocity vector cloud The velocity distribution of the variable cross-section conformal cooling channel is shown in Figure 15. The three velocity profiles with different diameter ratios difference is greater. In summary, the reasons for the formation of the velocity distribution and the pressure drop distribution are consistent, and the pressure drop in the channel is closely related to the velocity distribution.According to the temperature field distribution, pressure drop distribution and velocity distribution, it is shown that the heat transfer effect at D/d=1.4 is superior to that of other structures. Analysis of the results of equal cross section and variable cross section For the above three structures, the different diameter ratios are shown above, including the distribution of the overall and partial channel velocity.The flow rate of the water flow through the bent portion is relatively high.But in the bend of the channel, there will also be a swirl of water in some parts.There are also | 3,069,360 | 139117299 | 0 | 16 |
parts of the water that are almost stationary. It can be seen from the above velocity vector cloud diagram that when D/d=1.2, the variable flow rate is 1.25 m/s with the flow velocity in the channel, but the velocity is basically kept at 0.65 m/s.When D/d =1.4,reflected from the cloud, the flow of water through the curved part of the flow rate is relatively high, about 1.13 to 1.22 m/s. The cloud shows that the outlet speed of 0.515m/s, the speed difference between inlet and outlet is about 0.3 m/s; when D/d =1.6, compared with the velocity diagram of the previous two structural parameters, the velocity of the water flow decreases obviously.The velocity of the inlet is 0.8 m/s, and the maximum water velocity in the water flow is about 1.0 m/s; but the minimum outlet speed is 0.25 m/s; the speed difference between inlet and outlet is about 0.55 m/s.Compared to the previous two cases, the speed difference is greater. In summary, the reasons for the formation of the velocity distribution and the pressure drop distribution are consistent, and the pressure drop in the channel is closely related to the velocity distribution.According to the temperature field distribution, pressure drop distribution and velocity distribution, it is shown that the heat transfer effect at D/d=1.4 is superior to that of other structures. According to the structural diagram, the coolant enters from the left end and flows from the right end.The diameter of the left pipe is small and the diameter of the right pipe is larger.In order | 3,069,361 | 139117299 | 0 | 16 |
to reduce the non-uniformity cooling caused by the asymmetry of the structure, the enhanced heat transfer structure of the opposite arrangement of two adjacent channels is adopted, and its structure is shown in Figure 16.By comparing the variable cross-section channels in different arrangement directions under the same size conditions, it is possible to determine which type of watercourse in the same size has a better heat transfer effect. The temperature cloud of equal cross section and variable cross section with comformal channel Through the analysis of the product temperature of the variable cross-section channel injection mold with different parameters, the heat transfer and cooling effect of the injection mold of the variable cross section water channel is the best when the structural parameter is D/d = 1.4; but to find out which has a better cooling effect between the same direction and the opposite arrangement of the variable cross section watercourse, the cross-section channel and the optimized crosssection are simulated and the temperature field cloud image is obtained, as shown in Figure 17. As shown in Figures 17 and 18, from the temperature distribution, we can see that the overall temperature distribution is roughly the same and more uniform in these three enhanced heat transfer structures.As the channel is far from the tail of the product, there is insufficient cooling at the end of the product.So, it can be seen that the three enhancement heat transfer structures have a residual heat concentration.In Figure a, the maximum temperature of the enhanced channel water transfer is 336k, and | 3,069,362 | 139117299 | 0 | 16 |
the average temperature is 318.2K; the lowest temperature is 305 K.In Figure 19b and c, the maximum temperature of the two variable cross-section channel mold products is 321 and 319 K respectively, and the average temperature is 309.7 and 312.3 K, respectively; the lowest temperatures are 304 and 306 K, respectively.After comparing the three temperature distributions, we found that the heat transfer effect of the diagonal channel in Figure b was the best, and the heat transfer effect was much higher than that of the cross section.Based on the results of the temperature field distribution, these three enhanced heat transfer structures are derived from the change of the internal structure of the channel due to the basic structure of the channel.Through the simulation analysis on fluent, and comparison with the actual theoretical analysis, it is concluded that the cross section of the channel is different, and different arrangement is important to strengthen the heat transfer. Pressure drop of equal cross section and variable cross section The pressure drop in the cooling channel is shown in Figure 19.The pressure of the water inlet is higher than the pressure of the water outlet.In Figure 19a, the pressure at the inlet is at most 1140 Pa and the outlet pressure is 217 Pa, so the pressure drop across the channel reaches 923 Pa.In Figure 19b, the inlet pressure is 748 Pa, the outlet pressure is 120 Pa, pressure drop of about 648 Pa can be obtained.In Figure 19c, the inlet pressure is 735 Pa, the outlet pressure is 212 | 3,069,363 | 139117299 | 0 | 16 |
Pa, and the pressure drop is about 523 Pa.From the pressure drop graph, we can see that the pressure drop in graph a is the largest, and the energy loss of the flow in the cooling stage is very large.However, the energy loss is different from that in Figure a.So, from the pressure drop, we can conclude that the heat transfer effect of the opposite arrangement and the opposite direction are close. Flow velocity vector cloud of equal cross section and variable cross section The simulated fluid flow velocity of the three channel structures is shown in Figure 20.As shown in Figure 20, the maximum flow rate in the equal cross section conformal channel is 1.29 m/s, and the lowest flow rate is 0.58 m/s; then the average flow speed of 0.64 m/s.The maximum water velocity in the two channels with variable crossings is 1.74 and 1.46 m/s, and the minimum flow rate is 0.52 and 0.44 m/s, respectively; the average water velocity is 0.68 and 0.66 m/s.The velocity of the water flow through the curved part of the three graphs is relatively high: 1.03, 1.13 and 0.94 m/s; but at the bend of the channel, the water velocity is almost zero, and in some places there will be a swirl of water.It can be seen that the variable cross section with different arrangement has better heat transfer effect, by comparing the water flow velocity and pressure drop in the channel. Heat transfer and resistance performance test and analysis In this paper, the experimental study of | 3,069,364 | 139117299 | 0 | 16 |
heat transfer with variable cross-section channel and equal section channel is carried out.The experimental results are shown in Figure 21.Under the condition of the same water velocity, the enhanced heat transfer coefficient of the variable cross-section channel is obviously greater than that of the equivalent section channel.When the curve is flat, the heat transfer coefficient h of the variable section waterway with structural parameters (D/d=1.2,D/d=1.4,D/d=1.6,D/d=1.4) is increased by about 1.12, 1.29, 1.21 and 1.32 times than that of the equal cross-section channel, respectively.The relationship between pressure drop and flow rate is shown in Figure 22.It can be seen that the relationship between pressure drop and flow rate is approximately parabola, which is consistent with the theory.With the increase of flow velocity, it means the erosion of the wall surface and the increase of the resistance loss when the fluid flows through the water channel, so the pressure drop increases.With the increase of the channel Figure 3 . Figure 3.When D/d=1.2, the structure of the variable cross-section. Figure 4 . Figure 4.When D/d=1.4, the structure of the variable cross-section. Figure 5 . Figure 5.When D/d=1.6, the structure of the variable cross-section. Figure 7 . Figure 7.The relationship between average Nu number and spacing. Figure 10 .Figure 11 . Figure 10.Thermal conductivity of variable cross-section coolant inlet and outlet Figure 12 . Figure 12.Temperature profile of variable cross-section cooling products. Figure 13 . Figure 13.Temperature field distribution of longitudinal cross section (y = 0) for variable cross-section cooling products. Figure 14 . Figure 14.Pressure drop distribution of variable | 3,069,365 | 139117299 | 0 | 16 |
cross-section cooling products. Figure 15 . Figure 15.Velocity distribution of water flow in variable cross-section conformal cooling channel. Figure 17 . Figure 17.Temperature field distribution of the product. Figure 19 . Figure 19.The pressure drop of conformal cooling channel. Figure 20 . Figure 20.The flow velocity vector of the conformal cooling channel.A) Velocity of water flow in the equal cross section of the channel; b) velocity of water flow in the variable cross section of the channel with opposite direction; c) velocity of water flow in the variable cross section of the channel with the same direction. Figure 21 . Figure 21.Curve of the relationship between h and the velocity of water flow. Figure 22 . Figure 22.Comparison of pressure drops at different velocity of water flow. Table 3 . Structural parameters of variable cross-section channel. Table 4 . Grid quality and the number of units statistics. | 3,069,366 | 139117299 | 0 | 16 |
Flora richness of a military area: discovery of a remarkable station of Serapiasneglecta in Corsica Abstract One of the central issues in conservation today is identifying areas rich in biodiversity for priority conservation. On a global scale, the Mediterranean area is a biodiversity hotspot and, locally, Corsica contains high biodiversity with interesting sites for conservation. An inventory of flora was undertaken on the Solenzara military airbase. Five hundred and fifty-two plant species were inventoried, which represent an important species richness. Amongst these species, certain are rare or endemic. A large population of Serapiasneglectasubsp.neglecta was found and the size of this population was estimated. This species is localised at a global scale and has a protection status. This is the largest population known, with more than 155,000 individuals on the 550 ha of the airbase. Nineteen plant species have national protection status and 15 are classified as invasive alien species. The Solenzara airbase has a role in conserving many species; a management plan would be appropriate. Introduction In situ conservation can take different forms: at the species level, it is possible to select the most vulnerable species and develop conservation programmes to improve the conservation status of these target species (Guyot and Muracciole 1995, Fenu et al. 2020, Fišer et al. 2021. However, it is impossible to conserve all plant species through specific programmes, especially for funding and logistical reasons. Another approach is to focus conservation efforts on priority areas and preserve the whole community present in these areas (Coates and Atkins 2001, Bonn and Gaston 2005, | 3,069,367 | 247120191 | 0 | 16 |
Fenu et al. 2010, Zhang et al. 2017). This can be done by creating protected areas with varying degrees of constraints to conserve the present biodiversity. These two approaches are perfectly compatible and complementary in practice: conservation plans targeting certain species can be implemented in protected areas (Heywood et al. 2018). On a global scale, biodiversity hotspots have been defined as areas where biodiversity is significant, generally with a high level of species richness and endemism (Myers et al. 2000). One of the priority areas defined by Myers is the Mediterranean Basin. The many islands in the Mediterranean Basin have allowed high endemism due to their geographical isolation (Thompson et al. 2005). It is, therefore, relevant to look for priority areas for conservation within these hotspots, which could be defined as hotspots within hotspots (Cañadas et al. 2014). Corsica is an island of 8748 km² situated in the Mediterranean Basin. This Island is a flora refugia and a biodiversity hotspot, due to its location and history (Medail and Quezel 1997, Médail and Diadema 2009, Lestienne et al. 2019. The Corsican landscapes vary with massifs exceeding 2300 m of altitude (Jeanmonod and Gamisans 2007) with certain hotspots (Vogt-Schilb et al. 2016, Schatz 2017. The Corsican flora is well-known notably thanks to Jeanmonod and Gamisans (2007) and the various analyses carried out from this flora (Jeanmonod et al. 2009, Schlüssel et al. 2014, Jeanmonod et al. 2015. Corsican flora is composed of 2238 indigenous taxa, with 302 sub-endemic taxa. It faces certain threats, like land planning, pastoral abandonment | 3,069,368 | 247120191 | 0 | 16 |
or the introduction of invasive species. It is, thus, necessary to protect this rich flora (Jeanmonod and Gamisans 2007). We are interested in a military base in Corsica. Indeed, military bases are important areas for biodiversity because they are closed to the public, are not heavily impacted and these areas have soils that are often poorly fertilised and untreated due to old installations, so they often have high biodiversity (Warren et al. 2007, Seitre 2017, Massó et al. 2019. Military bases represent a significant part of the surface of the Earth (1-6%) (Zentelis and Lindenmayer 2015). However, they are military training areas with regular disturbances, which finally create a mosaic of habitats and the large surface areas allow for spacing of disturbances. Pioneer species and later species in the plant formations can settle and persist in these conditions (Warren et al. 2007). Therefore, they are often areas of high plant biodiversity and can play an essential role in the conservation of flora. To this end, it is necessary to know what is at stake in these areas, which are not accessible to the public. Knowledge of the issues at stake makes it possible to suggest favourable management and enhance the populations of rare or threatened species. Furthermore, it is necessary to allow military activities to co-exist with conservation activities, leading to conflicts (Lee Jenni et al. 2012). Our main goals are: 1) to elaborate a checklist of vascular flora in the airbase of Solenzara to better assess the floristic richness and the conservation priorities of this | 3,069,369 | 247120191 | 0 | 16 |
area; and 2) to quantify the considerable population of Serapias neglecta De Not., which is a protected sub-endemic species of orchid, highly remarkable on the airbase. Rich plant biodiversity is expected due to the geographical location and use of the area. The list of species in the Solenzara military zone contributes to the knowledge of the flora in this sector, to which access is restricted and regulated, making it possible to understand better and locate the challenges of this zone and best conserve the remarkable species. Study site and local context Our study area is localised in the Mediterranean Basin, one of the 25 biodiversity hotspots (Myers et al. 2000), where the flora is diversified, with a high level of endemism (Médail and Verlaque 1997). Moreover, the Mediterranean Basin is composed of several islands. Due to their insular nature, these islands contain much of the species richness of the Mediterranean area (Kier et al. 2009, Médail and Diadema 2009, Schatz 2017. Flora richness in Corsica, where our study area occurs, is higher than in metropolitan France (0.29 taxon per km² in Corsica and 0.09 taxon per km² in France) and endemism is important, with 5.9% strictly endemic plants and 13.5% sub-endemics (Gamisans and Jeanmonod 1995). Our study site is the airbase called n°126 Solenzara, a French Air Force base, located at Ventiseri (Fig. 1) and was created in 1952 by the North Atlantic Treaty Organisation (NATO) (Giannini 2019). NATO chose this area because it is airspace with little traffic and marshy areas are suitable for test | 3,069,370 | 247120191 | 0 | 16 |
firing. Major military development work was undertaken after 1956, including the drying out of wetlands. For the airbase, the draining of these wetlands appears to have benefited from a significant input of topsoil from major road infrastructure works carried out before 1973 (Bonfond 2018, Giannini 2019. This airbase is about 2 km wide (east-west axis) and about 3.3 km long (north-south axis) and it is located approximately 40 km north of Porto-Vecchio, on the east coast of Corsica. The Palo Pond (Ramsar site) surrounds the airbase in the north, the Travo River in the south, a dune site and the Mediterranean Sea in the east and a national road and an urbanised area to the west. The inventory takes place in the entire airbase, including the wetland area east of the beach (this second part corresponding to a site protected by the Conservatoire du Littoral). The total area surveyed is about 550 ha. This study area is a military site, which implies that it is closed to the public. It is also an airport area. Airports are interesting for biodiversity; lawns around strips are particularly favourable to orchids (Seitre 2017). Indeed, most runways are bordered by open grasslands, managed by regular mowing for aeronautical safety reasons. There are three main parts to the airbase. The westernmost part consists of buildings and low grasslands, with some woodland. In the central area, the landing strips are surrounded by low vegetation, regularly maintained by mowing. Finally, the easternmost part consists of wetlands and scrub. A de-sodding exercise was carried | 3,069,371 | 247120191 | 0 | 16 |
out in 2019 in this third part. The airbase is located in the coastal and thermomediterranean belts. These belts are rich in plant species, particularly the thermomediterranean belt (Schlüssel et al. 2014). Sampling method Several floristic inventories have been carried out and are compiled here to give an almost exhaustive list of the flora present on the airbase. Since 2017, the Ecotonia Consultancy has regularly intervened on the airbase to carry out floristic inventories. From 2017 to 2019, the inventories focused on the central area, around the runways and the northeast wetland (These inventories took place in March, April, May and October). In 2020, a complete inventory of the wetland was conducted (March to June). In 2021, an inventory took place in the northwest and another in the southwest of the airbase (March to June). This completed the data acquired since 2017. Then, we added floristic data acquired by the Corsican National Botanical Conservatory (CBNC), following inventories conducted in 2018 and 2019 (May to July) (Delage and The objective of the inventories was to conduct a systematic sampling to determine all species present in the study area. This allowed us to determine a precise list of taxa present. We then compared this list to the protected and threatened species list (decree of 20 January 1982, modified by the decree of 31 August 1995; decree of 24 June 1986 in French law) Hugot 2015, UICN France et al. 2018). We noted the degrees of endemism and rarity for each species given by the Flora Corsica determination key | 3,069,372 | 247120191 | 0 | 16 |
Gamisans 2007, Jeanmonod et al. 2009). For several species, the subspecies is not specified in the list we have established. We have chosen to take the lowest degrees of rarity in the Flora Corsica determination key: we likely contacted the most common subspecies. We have taken the corresponding degree of endemism. To find out the proportion of endemic species, we removed non-native species. Finally, we compared the list with the invasive alien species list of Corsica (Petit and Hugot 2019). Estimation of the density of Serapias neglecta Amongst inventoried species, we found a large population of Serapias neglecta, a nationally protected species of orchid (Fig. 2). Its range is limited to the extreme south-east of mainland France, Corsica (mainly around the south coast) and Sardinia, Sicily, the extreme south-east of Italy and along the east coast of the Adriatic (Croatia, Albania and Greece) (Delforge 2016). We estimated the size of the population. Firstly, we defined by cartography using the software QGIS the favourable areas for S. neglecta. We defined five large homogeneous zones: • The edges of runways: the vegetation is regularly mowed; the environment is very favourable to Serapias. • Wetlands: Serapias grow in smaller quantities, but are present. • Lawns near buildings: these lawns are regularly maintained. There is little competition and Serapias are numerous. • The south-western zone: vegetation is high. Serapias are present in a few places, but in reduced quantity. • The north-western zone: Serapias are present, but scattered. The vegetation is closing in. We chose a representative area of at | 3,069,373 | 247120191 | 0 | 16 |
least 600 m² in each homogeneous zone, where we made an exhaustive count. We then extrapolated the number of S. neglecta per area. Flora composition The 552 taxa found in the study area belong to 279 genera and 74 plant families (Suppl. material 1). Amongst these taxa, there are 45 sub-species, 503 species, four varieties and one hybrid. The families with the most species are Fabaceae (90 species), Poaceae (69 species) and Asteraceae (52 species) (Fig. 3). The genera with the most species are Trifolium (28 species), Carex (13 species), Juncus (13 species) and Vicia (13 species). Only 2.5% of species are sub-endemic and none is strictly endemic. Many protected species are present on the base and 19 species benefit from national protection, representing 3.4% of the plant taxa on the airbase. There are also 15 invasive alien species, representing 2.7% of the taxa present. More than 70% of the species in the database are common (C) or very common (CC) (Fig. 4). Only 8.6% are rare (R) or very rare (RR). Presence of a remarkable population of Serapias neglecta A large part of the base is favourable to S. neglecta: the population extends on both sides of the runways and the lawns near the buildings and wetlands. There are also several other orchid species: S. cordigera L., S. parviflora Parl., S. lingua L., Anacamptis morio (L.) The estimated area favourable to S. neglecta is 160 ha on the entire airbase. We assessed the density on different locations: 0.12 S. neglecta/m² on the edge of the | 3,069,374 | 247120191 | 0 | 16 |
runways, 0.009 S. Flora richness of a military area: discovery of a remarkable station of ... neglecta/m² in the wetlands, 0.2 S. neglecta/m² on the lawns near the buildings, 0.007 S. neglecta/m² in the south-western zone and 0.05 S. neglecta/m² in the north-western zone. Extrapolating, we estimate that the population of S. neglecta is at least 155,000 individuals on the entire airbase. This estimate is probably underestimated due to the nature of the species. Indeed, the individuals do not flower every year. We, therefore, see only a fraction of the population present. Depending on the year, densities of Serapias have been very variable. In 2019, the winter was arid (especially during the previous winter and spring), which was not favourable to orchids; during this year, we only observed hundreds of Serapias. Almost no individuals were visible in the spring on the airbase. Between 2020 and 2021, we compared the density of an area particularly rich in Serapias of about 900 m². The number of individuals was 2.5 times higher in 2021 than in 2020 (0.28 S. neglecta/m² in 2020 versus 0.81 in 2021). Other remarkable species Some species are remarkable for their status: for example, Gratiola officinalis L. is classified as vulnerable (VU). There are 13 species classified as near threatened (NT). Red List. This species is also sub-endemic and rare in Corsica. Four nationally-protected species and very rare in Corsica are found: Trifolium cernuum Brot., Gratiola officinalis L., Ranunculus lingua L. and Anemone coronaria L. Finally, Salix apennina A.K.Skvortsov is very rare and Serapias olbia | 3,069,375 | 247120191 | 0 | 16 |
Verg., Sagina subulata var. gracilis Foucaud & Simon and Ranunculus revelierei are rare. These three species are also sub-endemic. Ranunculus revelierei Boreau have national protection and is NT on theCorsican IUCN One subspecies is to be considered as potential on the airbase; Bromus hordeaceus subsp. thominei (Hardouin) Braun-Blanq. This subspecies is present in Corsica, but challenging to determine. We consider it as potential, but it has not been taken into account during the analyses. Sagina subulata (Sw.) C.Presl belongs to the huge family of Caryophyllaceae. Two subspecies exists: S. subulata subsp. revelierei (Jord. & Fourr.) Rouy & Foucaud, an endemic Corso-Sardinian orophyte and S. subulata subsp. subulata (Sw.) C.Presl, a southern and western European species. The latter is currently divided into two varieties, one of which is present throughout its range (var. subulata (Sw.) C.Presl), but the other is not known: var. gracilis Foucaud & Simon. It is only reported in France (Provence and Corsica), although it is potentially present elsewhere (Sardinia, Tuscany, Liguria, Spain). It is found in a singular environment: shallow temporary ponds with siliceous substrates in the Mediterranean climate. This environment, which is highly stressful for a plant, has led this taxon to adopt a therophyte biological type -its life is limited to a few weeks or months, whereas var. subulata is hemicryptophytic. This adaptation is typical of Mediterranean environments and seems to be an important evolutionary event that may justify this variety being treated at a higher taxonomic rank soon. If specific research is carried out, it could one day lead to | 3,069,376 | 247120191 | 0 | 16 |
the description of a new high-ranking taxon (species or subspecies), whose worldwide distribution area would at best be restricted, or even endemic, to the French Mediterranean region. In Solenzara, this tiny plant has found unusual secondary habitats: the ruts made by vehicles driving on the base. Other annual species accompany it with similar ecologies, some of which are rare: Ranunculus revelierei, Lotus conimbricensis Brot., Solenopsis laurentia (L.) C.Presl, Lysimachia minima (L.) U.Manns & Anderb. and Lythrum portula (L.) D.A.Webb. Discussion The Solenzara airbase is rich in plant species. Its location explains this richness since Mediterranean islands have high biodiversity (Medail and Quezel 1997, Kier et al. 2009, Médail and Diadema 2009. It is also explained by the nature of the area since military areas often have a high level of species richness (Warren et al. 2007, Zentelis and Lindenmayer 2015, Massó et al. 2019), but also because this is an airbase: airports generally harbour a high level of biodiversity, particularly of orchids (Seitre 2017). Airports are usually mown regularly for safety reasons related to aircraft traffic; this mowing, especially near runways, favours species with little competition, such as orchids. It is, therefore, not surprising to find protected and remarkable species amongst this richness. We have shown that 23.2% of the indigenous taxa present in Corsica are present on the military base of Solenzara, on only 550 ha. In comparison, 688 species were inventoried on the 16,175 ha of the Hohenfels training area in Germany, which represents 27% of the species richness of Bavaria (Warren et al. | 3,069,377 | 247120191 | 0 | 16 |
2007). This military area is almost 30 times larger than the Solenzara airbase. There are 302 sub-endemic taxa, 688 rare and very rare taxa, 191 taxa with a protection status and 64 invasive species in Corsica (Jeanmonod and Gamisans 2007, Jeanmonod et al. 2009, Petit and Hugot 2019. This represents a significant proportion of these categories, given the small surface area of the airbase. Thus, 6.5% of the rare taxa, 4.3% of the sub-endemic taxa (9.8% if we consider only the 133 taxa of the littoral and thermo-Mediterranean belts) and 10.0% of the protected taxa of Corsica are present on the airbase. On the other hand, 23.4% of the invasive species of Corsica are present on the airbase. To a large extent, this sector represents a control zone for the flora of the eastern coast of Corsica before urbanisation, which is locally very close. However, this base was created on the former delta area of the Travo River, which explains the shallow soil on a pebble bed. This particular situation probably limits the presence of several other species and makes the diversity of this site even more exceptional. Proportions of endemic and rare species are not negligible; moreover, we have noted the presence of species to be conserved as a priority. We presented the exceptionally abundant population of Serapias neglecta, which is the largest known to date. More generally, orchids are present in all areas maintained by mowing in the airbase (12 different species of orchids). Other species as Ranunculus revelierei are also remarkable and deserve | 3,069,378 | 247120191 | 0 | 16 |
better consideration. Military activities (napalm use, nuclear weapons, conflicts) are often considered as threats to biodiversity (Lawrence et al. 2015, Massó et al. 2019. However, despite these negative impacts, military areas can be an opportunity for biodiversity conservation. It is not always easy because, for the military, it is not acceptable to restrict the training of soldiers because of environmental constraints (Lee Jenni et al. 2012). The airbase has a role to play in the conservation of these species. On this military base, training areas are small and localised and there are still many natural areas. It is, therefore, entirely possible to set up conservation actions for remarkable species. Currently, the management of the base allows orchid populations to extend. However, improvements are possible and there are areas where management can be targeted to benefit these species. A management plan that promotes plant biodiversity on the airbase, considering the issues, could further increase the richness and perhaps promote rare or endemic species present near the airbase. There is also a need for a management plan to control invasive species. The Solenzara airbase can be considered as a biodiversity reserve; there is little human activity, some areas being very infrequently visited (Médail and Verlaque 1997). This is a real opportunity for plant conservation. This richness gives the military base a responsibility for conserving this natural heritage; this situation should be recognised by a protection status for this site used in France (such as APHN: Decree of natural habitat protection or APPB: Decree prefectoral of biotope protection). | 3,069,379 | 247120191 | 0 | 16 |
Temporal patterns of lipoperoxidation and antioxidant enzymes are modified in the hippocampus of vitamin A-deficient rats. Animals can adapt their behavior to predictable temporal fluctuations in the environment through both, memory-and-learning processes and an endogenous time-keeping mechanism. Hippocampus plays a key role in memory and learning and is especially susceptible to oxidative stress. In compensation, antioxidant enzymes activity, such as Catalase (CAT) and Glutathione peroxidase (GPx), has been detected in this brain region. Daily rhythms of antioxidant enzymes activity, as well as of glutathione and lipid peroxides levels, have been described in brain. Here, we investigate day/night variations in lipoperoxidation, CAT, and GPx expression and activity, as well as the temporal fluctuations of two key components of the endogenous clock, BMAL1 and PER1, in the rat hippocampus and evaluate to which extent vitamin A deficiency may affect their amplitude or phase. Holtzman male rats from control, vitamin A-deficient, and vitamin A-refed groups were sacrificed throughout a 24-h period. Daily levels of clock proteins, lipoperoxidation, CAT and GPx mRNA, protein, and activity, were determined in the rat hippocampus obtained every 4 or 5 h. Gene expression of RARalpha and RXRbeta was also quantified in the hippocampus of the three groups of rats. Our results show significant daily variations of BMAL1 and PER1 protein expression. Rhythmic lipoperoxidation, CAT, and GPx, expression and activity, were also observed in the rat hippocampus. Vitamin A deficiency reduced RXRbeta mRNA level, as well as the amplitude of BMAL1 and PER1 daily oscillation, phase-shifted the daily peak of lipoperoxidation, and had a differential | 3,069,380 | 21239645 | 0 | 16 |
effect on the oscillating CAT and GPx mRNA, protein, and activity. Learning how vitamin A deficiency affects the circadian gene expression in the hippocampus may have an impact on the neurobiology, nutritional and chronobiology fields, emphasizing for the first time the importance of nutritional factors, such as dietary micronutrients, in the regulation of circadian parameters in this brain memory-and-learning-related region. INTRODUCTION Animals can adapt their behavior to predictable temporal fluctuations in the environment such as day/night period, temperature, food and water availability, risk of predation, through both, memory-and-learning processes and an endogenous time-keeping mechanism (Pravosudov and Clayton, 2002;Panda et al., 2003;Wiskott et al., 2006;Maiti et al., 2008). Time-of-day effects on learning and memory have been observed in human and rats (Winocur and Hasher, 2004). Hippocampus plays a key role in memory and learning and is especially susceptible to oxidative stress (Onodera et al., 2003;Cheng et al., 2004). In compensation, there is wide evidence of antioxidant enzymes, Catalase (CAT), Glutathione peroxidase 1 (GPx1) and Superoxide dismutase (SOD), activity in this brain region (Baydas et al., 2002;Manikandan et al., 2005). Interestingly, daily rhythms of SOD, GPx, and Glutathione reductase (GR) activities, as well as of glutathione (GSH) and malondialdehyde (MDA) levels, have been demonstrated in brain (Pablos et al., 1998;Baydas et al., 2002). Lipid peroxides, a damaging product of reactive oxygen species (ROS) reaction on cellular lipids, are particularly elevated in brain (Noda et al., 1983;Triggs and Willmore, 1984). It has been reported that oxidative damage and increase in lipoperoxidation may induce a decline of cognitive function in | 3,069,381 | 21239645 | 0 | 16 |
cerebral cortex and hippocampus (Onodera et al., 2003) and that some prooxidant agents such as propionic acid, aluminum, ozone and aging, provoke oxidative stress and modify the antioxidant defense system causing an imbalance in the cellular redox state and impairment of learning and memory in hippocampus (Pettenuzzo et al., 2002;Gómez et al., 2005; Barhwal et al., 2007). In the seventies, it was demonstrated that memory performances for associative learning oscillate in a circadian fashion across time, with high memory retention at multiples of 24 hours post-learning (Holloway and Wansley, 1973). This fluctuation was absent in suprachiasmatic nucleus (SCN)-lesioned rats, implicating the underlying role of the endogenous biological clock (Stephan and Kovacevic, 1978). Even though the mammalian central clock is located in the SCN, most of the tissues and cells, if not all of them, have the molecular components of the circadian clock. The molecular clock machinery works through two interacting transcription/translation-based feedback loops, a positive and a negative one. The positive loop is constituted by the heterodimeric basic helix-loop-helix-Per Arnt Sim (bHLH-PAS) transcription factor: BMAL1:CLOCK (from Brain and Muscle ARNT Like protein 1: Circadian Locomoter Output Cycles Kaput protein) which binds to Ebox enhancers (CANNTG) to activate the transcription of other clock and clock-controlled genes (Reppert and Weaver, 2002). Thus, in mammalian cells, the BMAL1:CLOCK heterodimer drives the rhythmic transcription of three clock Period genes (Per1, Per2, and Per3), two clock Cryptochrome genes (Cry1 and Cry2) as well as other clock and clock-controlled genes . As Per and Cry mRNAs are translated and proteins accumulate in | 3,069,382 | 21239645 | 0 | 16 |
the cytoplasm, they form PER-CRY complexes which, once phosphorylated, translocate into the nucleus, interact with BMAL1:CLOCK and inhibit BMAL1:CLOCK-mediated transcription of clock and clockcontrolled genes, a general mechanism conserved in many organisms (Reppert and Weaver, 2002;Panda and Hogenesch, 2004;Lee et al., 2004). Additionally, Rutter et al. (2001) have shown that a high NAD(P)H/NAD(P) + ratio, which can be the product of a well balanced cellular redox state, favors BMAL1:CLOCK heterodimerization as well as its DNA binding in an in vitro system. Vitamin A is a micronutrient involved in a wide spectrum of biological functions. More recently, a role for a vitamin A oxidized derivative, the retinoic acid (RA), has been established in phenomena related to higher cognitive function in the adult mouse brain (Etchamendy et al., 2003, Husson et al., 2004. Besides their role as antioxidants and radical scavengers (Palacios et al., 1996;Anzulovich et al., 2000), Vitamin A and its derivatives, the retinoids, regulate most of the developmental, physiological and cellular processes by activating retinoid nuclear receptors. Thus, retinoids act through RA receptors (RARs, α, β and γ) and Retinoid X receptors (RXRs, α, β, and γ), and while RARs bind both all-trans-RA (ATRA) and 9cis-RA, RXRs only bind 9cis-RA (Heyman et al., 1992). It is now known that, in the case of RARs and RXRs, transcription regulation is mediated either by RAR:RXR heterodimers or by RXR:RXR homodimers, which bind to RAREs and RXREs, respectively, on their target gene promoters (Soprano et al., 2004). Noteworthily, ATRA has been detected at relatively high levels in the central | 3,069,383 | 21239645 | 0 | 16 |
nervous system of adult rats, and the hippocampus/cortex area contains the highest proportion of RA in the brain (Werner and Deluca, 2002). Additionally, high expression of the retinoid receptors, RARα, RARγ and RXRβ, has been observed in the adult mouse hippocampus (Krezel et al., 1999, Zetterstrom et al. 1999) and it has been demonstrated that vitamin A deficiency deteriorates LTP, leading to learning and memory impairment, by reducing the expression of RARβ and RXRβ in the mouse and rat hippocampus (Etchamendy et al., 2003, Mao et al., 2006. Day-night cycles are known as the main zeitgeber for a wide number of living beings, but it has been shown that also feeding cycles can entrain peripheral clocks, independent of light entrainment (Brewer et al., 2005). While the mechanism could remain unknown, examples of hormonal phase-shifting of circadian gene expression in peripheral organs begun to emerge with Balsalobre et al. (2000). Indeed, there is some evidence that in a liganddependent manner retinoid receptors can interact with the cellular clock machinery partners, CLOCK, or its homolog MOP4, and inhibit BMAL1:CLOCK and/or BMAL1:MOP4 heterodimer-mediated expression of circadian responsive genes (McNamara et al., 2002). Above observations raise the possibility that nutritional factors might have an effect on the clock activity and circadian expression of target genes, for example, by modulating cellular redox state and/or BMAL1:CLOCK DNA-binding activity. Considering, vitamin A deficiency: a) produces oxidative stress, increasing lipid peroxidation levels and affecting antioxidant enzymes activities , b) reduces the availability of retinoid nuclear receptors (Husson et al., 2003 and thus affecting the | 3,069,384 | 21239645 | 0 | 16 |
activity of cellular clock machinery partners such as CLOCK and BMAL1 (McNamara et al., 2002), and c) produces learning and memory impairments (Etchamendy et al., 2003, Mao et al., 2006, our objective was to evaluate the effect of vitamin A deficiency on the daily variation of clock gene expression, lipoperoxidation, and antioxidant defense systems, in the rat hippocampus, a peripheral oscillator with a crucial role in cognitive function. Here, we show daily rhythmic expression of BMAL1 and PER1 clock components, and describe, for the first time at our knowledge, daily fluctuations in CAT and GPx expression as well as in their enzymatic activities in the rat hippocampus. Vitamin A nutritional deprivation not only modified BMAL1 and PER1 circadian expression, but also altered the day-night cycles of lipoperoxidation and antioxidant enzymes expression and activities, in this brain memory-and-learning-related region. Animal Model and Diet Male Holtzman rats were bred in our animal facilities (National University of San Luis, Argentina), and maintained in a 21-23°C controlled environment with a 12h-light:12h-dark cycle. They were weaned at 21 days of age and immediately assigned randomly to either the experimental diet, devoided of vitamin A (vitamin A-deficient group) or the same diet with 4000 IU of vitamin A (8 mg retinol as retinyl palmitate) per Kg of diet (control group). Feeding the animals with a vitamin A-free diet during three months, guarantees subclinical plasma retinol concentration and depleted retinol stores in liver Oliveros et al, 2000). At the end of the third month of treatment, half of the vitamin Adeficient rats were | 3,069,385 | 21239645 | 0 | 16 |
subsequently fed on the complete diet during 15 days to induce repletion of vitamin A (vitamin A-refed group). This group was used to study the reversibility of the possible changes caused by the vitamin deficiency. Rats were given free access to food and water throughout the entire experimental period. All experiments were conducted in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals (NIH Publications No. 80-23) and the National University of San Luis Committee's Guidelines for the Care and Use of Experimental Animals. Diets were prepared according to the AIN-93 for laboratory rodents (Reeves et al, 1993). Both, vitamin A-deficient and control diets had the following composition (g/kg): 397.5 cornstarch, 100 sucrose, 132 dextrinized cornstarch, 200 lactalbumin, 70 soybean oil, 50 cellulose fiber, 35 AIN-93 mineral mix, 10 AIN-93 vitamin mix (devoided of vitamin A for the vitamin A-deficient diet), 3 L-cystine, 2.5 choline bitartrate, and 0,014 tert-butylhydroquinone. After the treatment period, six rats from each group were sacrificed at different time points throughout a 24-h period. Those time points are referred to as zeigeber times (ZT) with ZT=0 when animal room light is on. Hippocampi were removed on an ice-chilled plate, weighed and immediately placed in liquid nitrogen. All the experiments were repeated at least twice. Tissue homogenates and antioxidant enzymes activity Two pools of three left hippocampi each, extracted from control, vitamin A-deficient and vitamin A-refed rats at every time point (ZT2, ZT7, ZT12, ZT17 and ZT22), were homogenized in 1/5 (w/v) dilution in 120 mM | 3,069,386 | 21239645 | 0 | 16 |
KCl and 30 mM phosphate buffer, pH 7.2 at 4°C. Suspensions were centrifuged at 800 × g for 10 min at 4°C to remove nuclei and cell debris. The pellets were discarded and supernatants were used to determine antioxidant enzyme activities. CAT, GPx, and SOD activities were determined by the methods of Aebi (1984), Flohe and Gunzler (1984), and McCord and Fridovich (1969), respectively. Briefly, CAT activity was determined by measuring the decrease in the absorption at 240 nm when 100 μl of 3 mM H 2 O 2 were added to a reaction medium containing 50 mM phosphate buffer pH 7.3 and 1/500 dilution of enzymatic preparation. The pseudo-first-order reaction constant k′ (k′= k[CAT]) of the decrease in the H 2 O 2 absorption was determined and catalase activity was calculated using k= 4.6 × 10 7 M −1 s −1 (Chance et al, 1979) and expressed in IU/mg prot. One CAT unit is defined as the amount of enzyme required to decompose 1 μM of H 2 O 2 /min. GPx activity was determined following NADPH oxidation at 340 nm in a reaction medium containing 0.2 mM GSH, 0.25 U/ml yeast glutathione reductase, 0.5 mM tert-butyl hydroperoxide and 50mM phosphate buffer (pH 7.2). SOD activity was determined on the basis of its inhibitory effect on the rate of superoxide-dependent reduction of cytochrome c by xanthine-xanthine oxidase at 560 nm. The reaction medium contained 50 mM phosphate buffer (pH 7.8), 50 μM xanthine, 20 μM cytochrome c and xanthine oxidase to detect 0.025 absorbance units/min. | 3,069,387 | 21239645 | 0 | 16 |
One unit of SOD was defined as the amount of enzyme that inhibits cytochrome c reduction by 50%. Protein was measured by the method of Lowry et al. (1951) using bovine serum albumin (1mg/ml) as standard. All reagents were from Sigma-Aldrich Co. Lipoperoxidation levels Two pools of three left hippocampi each, extracted from control, vitamin A-deficient and vitamin A-refed rats at ZT2, ZT6, ZT10, ZT14, ZT18 and ZT22, were homogenized in 1/5 (w/v) dilution in 120 mM KCl and 30 mM phosphate buffer, pH 7.2 at 4°C. Suspensions were centrifuged at 800 x g for 10 min at 4°C to remove nuclei and cell debris. The pellets were discarded and supernatants were used to determine TBARs. Lipid peroxidation was quantified spectrophotometrically by determining MDA levels as thiobarbituric acid reactive substances (TBARS) according to Draper and Hadley (1990). mRNA isolation and RT-PCR Total RNA was extracted from three pools of two right hippocampi each. Hippocampus samples were isolated at ZT2, ZT6, ZT10, ZT14, ZT18 and ZT22 from control, vitamin Adeficient and vitamin A-refed rats. All RNA isolations were performed using the Trizol reagent (Invitrogen Co) as directed by the manufacturers. Gel electrophoresis and ethidium bromide staining confirmed the integrity of the samples. Quantification of RNA was based on spectrophotometric analysis at 260 nm. 3 μg of total RNA were reverse-transcribed with 200 units of MMLV Reverse Transcriptase (Promega Inc.) using random hexamers in a 25 μl reaction mixture and following manufacturer's instructions. Transcript levels of CAT, SOD and GPx were determined by RT-PCR and normalized to beta-actin | 3,069,388 | 21239645 | 0 | 16 |
as endogenous control. Fragments coding for μ-actin, CAT, SOD and GPx were amplified by PCR in 50 μl of reaction solution containing 0.2 mM dNTPs, 1.5 mM MgCl2, 1.25 U of Taq polymerase, 50 pmol of each rat specific oligonucleotide primer and RT-generated cDNA (1/5 of RT reaction). The sequences of the specific primers are shown on Table 1. Samples were heated in a thermalcycler (My Cycler, BioRad) to 94°C for 2 min, followed by 40 cycles of: (1) denaturation, 94° C for 1 min; (2) annealing, 59° C during 1 min; (3) extension, 72°C for 1 min. After 40 reaction cycles, the extension reaction was continued for another 5 minutes. PCR products were then electrophoresed on 2% (w/v) agarose gel with 0.01% (w/v) ethidium bromide. The amplified fragments were visualized under ultraviolet (UV) transillumination and photographed using a Cannon PowerShot A75 3.2MP digital camera. The mean of gray value for each band was measured using the NIH ImageJ software (Image Processing and Analysis in Java from http://rsb.info.nih.gov/ij/) and the relative abundance of each band was normalized according to the housekeeping β-actin gene, calculated as the ratio of the mean of gray value of each product to that of β-actin. Real Time PCR Relative quantification of RARα and RXRβ mRNA levels was performed by Real-Time PCR using the ABI Prism® 7500 thermocycler (Applied Biosystems, USA). Before the realtime PCR was performed, cDNA obtained by RT-PCR was diluted to 20ng/μl with nucleasefree water. The diluted cDNA (5μl) was amplified in a 25μl final volume reaction mix containing | 3,069,389 | 21239645 | 0 | 16 |
1X SYBR Green I fluorescent dye (Applied Biosystems, USA) and 500 nM gene-specific primers (Table 1). Reactions were subjected to one step of 95ºC for 5 min followed by 40 cycles of 95ºC for 15 sec and 60ºC for 1 min. Relative expression of the realtime PCR products was determined by the ΔΔCt method. This method calculates relative expression using the equation: Immunobloting Protein extracts were prepared from two pools of three left hippocampi each, obtained from each group of rats at ZT2, ZT6, ZT10, ZT14, ZT18 and ZT22, in buffer C (20 mM HEPES, pH 7.9, 0.42 M NaCl, 1.5 mM MgCl2, 0.2 mM EDTA, 0.5 mM dithiothreitol, 0.5 mM phenylmethylsulfonyl fluoride, 1 μg/ml leupeptin, 1 μg/ml of pepstatin, 1 mM sodium fluoride, 5 sM sodium orthovanadate, and 25% glycerol). Aliquots containing 40 μg of total protein were subjected to electrophoresis in 4-12% NuPageTM Bis-Tris gels (Invitrogen Life Technologies, Carlsbad, CA), and then transferred to Immobilon-PTM transfer membranes (Millipore, Bedford, MA). Immunoblot analyses were performed as described in the manufacturers' protocols for the detecting antibodies. Briefly, membranes were blocked in Blotto (5% nonfat dry milk, 10 mM Tris-HCl, pH 8.0, and 150 mM NaCl) followed by 3h incubation at RT with either goat anti-CAT, goat anti-GPx1, goat anti-BMAL1 or rabbit anti-PER1 antibodies (Santa Cruz Biotechnology, Santa Cruz, CA) in Blotto containing 0.05% thimerosal. After incubation with primary antibody, the membranes were washed in TBS (10 mM Tris-HCl, pH 8.0, and 150 mM NaCl) containing 0.05% Tween-20, before incubation with horseradish-peroxide-conjugated donkey anti-goat, or goat anti-rabbit, | 3,069,390 | 21239645 | 0 | 16 |
IgG (Santa Cruz Biotechnology, Santa Cruz, CA) diluted 1:10,000 in Blotto for 1 hour at room temperature. After washing, antibody/protein complexes on membranes were detected using Vectastain DAB Peroxidase Substrate kit from Vector Laboratories (Burlingame, CA) and following the manufacturers indications. The mean of intensity of each band was measured using the NIH ImageJ software (Image Processing and Analysis in Java from http://rsb.info.nih.gov/ij/). Scanning of antioxidant genes upstream regions for putative E-box, RARE and RXRE sites To identify putative E-box, RAR (RARE), and/or RXR (RXRE) DNA consensus regulatory sites, CAT, GPx and SOD gene regulatory regions, up to 2000 bp upstream of the translation start codon, were scanned for significant matches using the MatInspector software (Quandt et al., 1995) from Genomatix (http://www.genomatix.de). Statistical Analysis Time point data were expressed as means ± standard error of the mean (SE) and pertinent curves were drawn. Time series were computed by one-way ANOVA followed by Tukey's post-hoc test for specific comparisons. A P value of less than 0.05 between time points was considered to be significant. Effect of vitamin A deficiency on antioxidant enzymes mRNA expression in the rat hippocampus First of all, to test whether vitamin A deficiency could have any effect on the antioxidant enzymes transcript levels in the rat hippocampus, CAT, GPx and SOD mRNA expression was analyzed by RT-PCR ( Figure 1). We found vitamin A deficiency significantly decreased CAT and GPx mRNA levels in the hippocampus of rat (P<0.05 and P<0.01, respectively) and had no effect on SOD expression (data not shown), in comparison | 3,069,391 | 21239645 | 0 | 16 |
to controls. Moreover, 15 days of vitamin A refeeding restored transcript levels of CAT and GPx to control values. Daily patterns of lipoperoxidation and antioxidant enzymes in the rat hippocampus Once we confirmed vitamin A deficiency had an effect on CAT and GPx mRNA expression levels, we continued to test whether lipoperoxidation and antioxidant enzymes expression and activities followed a daily pattern in the hippocampus of rat. For that, samples were obtained throughout a 24h-period from control, vitamin A-sufficient, rats. Tissue extracts were prepared as described in the Materials and Methods section, and subjected to TBARS, RT-PCR, immunobloting and activity assays. The results revealed that lipoperoxidation (Figure 2, left panel) as well as mRNA expression, protein levels and activity of CAT ( Figure 3A, B and C, left panels) and GPx ( Figure 4A, B and C, left panels), follow a robust diurnal rhythm in the hippocampus of control rats. We found MDA levels peak at ZT22 (P<0.01), the end of the activity (and catabolic) phase in rodents. This peak of lipoperoxidation overlaps with the highest level of CAT activity, at ZT22 (P<0.005; Figure 3C, left panel), and concurs with the GPx activity peak at the end-ofthe-night/beginning-of-the-day, ZT22-ZT2, phase (P<0.001; Figure 4C, left panel). Diurnal rhythms were also observed in CAT and GPx mRNA expression and protein levels. Thus, the highest level of CAT mRNA expression is at ZT22 (P<0.001), preceding the maximal protein level observed at ZT10 (P<0.005; Figure 3A and B, left panels). In the case of GPx, transcript expression reaches its maximum at | 3,069,392 | 21239645 | 0 | 16 |
ZT2 (P<0.005) while protein level does it at ZT10 (P<0.001; Figure 4A ad B, left panels). Temporal pattern of lipoperoxidation in the hippocampus of vitamin A-deficient rats Interestingly, we observed a 12-hour phase-shift in the daily pattern of lipoperoxidation in the hippocampus of vitamin A-deficient rats, with MDA levels peaking at ZT10 (P<0.0001; Figure 2, central panel). Refeeding vitamin A-deficient rats with the control diet, shortened in 4 hours, but didn't completely reverted, the phase-shift observed in vitamin A-deficient animals in comparison to controls (Figure 2, right panel). Temporal expression and daily activity of CAT in the hippocampus of vitamin A deficient rats Daily rhythms of CAT gene and protein expression as well as enzymatic activity were essentially abolished, with no significant differences between values at different time points, in the hippocampus of vitamin A-deficient rats ( Figure 3A, B and C, central panels). Fifteen days of vitamin A refeeding reverted the effects of vitamin A deficiency and recovered daily rhythmicity of mRNA (P<0.001), protein levels (P<0.0001) and enzymatic CAT activity (P<0.001), although we observed some phase shifts of maximums in comparison to controls ( Figure 3A, B and C, right panels). Temporal expression and daily activity of GPx in the hippocampus of vitamin A deficient rats In this case, vitamin A deficiency phase-shifted the daily patterns of mRNA expression and enzymatic activity of GPx (P<0.01 and P<0.001, respectively; Figure 4A and C, central panels). Thus, GPx transcript level peak was phase shifted from ZT2 to ZT10 and GPx activity from ZT22 to ZT12. Fifteen days | 3,069,393 | 21239645 | 0 | 16 |
of vitamin A refeeding, start reversing the vitamin A deficiency effects on GPx expression and activity ( Figure 4A and C, right panels). Putative RARE, RXRE and E-box sites on CAT and GPx genes upstream region Scanning of 2000 bp upstream of the translation start codon of CAT, GPx and SOD in the Genomatix database (http://www.genomatix.de) revealed one RARE, two RXREs and five putative clock-responsive E-box elements on the CAT gene upstream region, while five RXREs and one E-box sites were found on the GPx gene upstream region ( Figure 5). None of these responsive sites was present on SOD promoter (data not shown). Interestingly, we also found a retinoic acid-related orphan receptor a (RORa) responsive site (RORE) on the GPx promoter. RARα and RXRβ expression levels in the hippocampus of vitamin A deficient rats Once we had knowledge about the presence of putative RARE, RXRE and E-box regulatory sites on the promoter of the CAT and GPx genes, continued to study the mRNA expression of retinoid nuclear receptors in the hippocampus of control, vitamin A-deficient and vitamin A-refed rats. Interestingly, vitamin A deficiency decreased the RXRβ transcript level (P<0.001), but had no effect on the RARα mRNA expression. Refeeding vitamin Adeficient animals with control diet during 15 days, increased RARa mRNA level (P<0.05) but was not enough to restore the RXRβ mRNA expression to control level (P<0.001) ( Figure 6). Daily rhythms of BMAL1 and PER1 expression in the hippocampus of vitamin A-deficient rats To test to which extent vitamin A deficiency could affect the | 3,069,394 | 21239645 | 0 | 16 |
circadian expression of key clock factors, we analyzed the protein levels of BMAL1 and PER1 during a 24-h period, in the hippocampus of control, vitamin A-deficient and vitamin A-refed rats. We observed BMAL1 and PER1 protein expression varies throughout a day in the rat hippocampus, with maximal protein levels at ZT22 and ZT2, respectively (Figure 7). Three months of vitamin A deficiency, reduced in 20% and 37% the amplitude of BMAL1 and PER1 oscillation, respectively (Figure 7). These effects were completely reverted after fifteen days of vitamin A refeeding. DISCUSSION Vitamin A is indispensable for CAT and GPx transcript expression in the rat hippocampus Vitamin A is linked to a variety of factors determining the susceptibility to oxidative stress. Previous results from our lab indicate that three months of feeding the vitamin A-free diet causes a well established vitamin A deficiency, with a significant reduction of the vitamin levels in the rat liver and heart, associated to alterations in non enzymatic and enzymatic antioxidant defense system Oliveros et al., 2000). Aerobic organisms developed a complex and efficient network of antioxidant defenses to protect themselves against deleterious effects of reactive oxygen species and maintenance of tissue and cellular homeostasis. It has been demonstrated that vitamin A modulates the upregulation of several major scavenger enzyme genes, such as glutathione transferase (Xia et al., 1996). Similarly, in the current study, we found mRNA levels of CAT and GPx1 were significantly lower in the hippocampus of vitamin A-deficient rats, compared to controls (Figure 1). Since alterations in the antioxidant defense | 3,069,395 | 21239645 | 0 | 16 |
system in the hippocampus have been seen to cause imbalance in the cellular redox state and impairment of learning and memory (Pettenuzzo et al., 2002;Gómez et al., 2005), our observations made us wonder about the participation of vitamin A in the circadian regulation of the antioxidant/pro-oxidant balance in the hippocampus and its putative relevance in the daily cognitive function. Relevance of daily rhythms of lipoperoxidation, antioxidant enzymes and clock proteins in the hippocampus Lipid peroxidation is a unique mode of oxidative injury which is triggered and promoted by different radical and non-radical members of the ROS family, or by the catalytic decomposition of preformed lipid hydroperoxides by several agents in different tissues (Niki et al, 2005). Here, we observed lipoperoxidation follows a daily rhythm in the hippocampus of control rats with a peak time of TBARS at the end of the catabolic-, thereafter ROS producing, activity-phase in rats. Thus, such increase in the level of lipid peroxides at the end-of-the-night/beginning-of-the-day could be explained as a consequence of oxidative metabolism during the dark phase, as seen by Baydas et al. (2002) in rat cerebral tissue. These observations are also consistent with temporal patterns of lipoperoxidation observed by Subramanian et al. (2008) and Pandi-Perumal et al. (2008) in the brain. Diurnal rhythms of antioxidant GPx, SOD and GR activity have been observed in the rat brain, particularly, in the cerebral cortex (Baydas et al., 2002). Moreover, Pablos et al. (1998) found rhythms of GPx and GR in the hippocampus of chick. Here, we report, for the first time | 3,069,396 | 21239645 | 0 | 16 |
at our knowledge, daily variation of CAT and GPx activity as well as rhythmic CAT and GPx expression, at transcript and protein levels, in the rat hippocampus (Figures 3 and 4, A, B, and C, left panels). It is well known that CAT eliminates H 2 O 2 , by reducing it to water and oxygen, and that GPx helps to prevent the formation of hydrogen and organic hydroperoxides, thus protecting the cell from damaging effects of those oxidizing species. As expected, temporal patterns of CAT and GPx activities observed in the rat hippocampus were consistent with the rhythm of lipoperoxidation. While the lowest CAT activity occurs during the light period and, at least in part, brings lipid peroxidation into the maximal level, highest CAT and GPx activities, practically concur with the nocturnal peak of lipoperoxidation. Thus, antioxidant enzymes would have a complementary and proper timing for protecting hippocampus against peroxides, maintaining lipoperoxidation at controlled fluctuating levels, with the lowest MDA concentration occurring during the diurnal, anabolic, period in rats (Figure 2, left panel). Studies made by Sani et al. (2006) and Baydas et al. (2002), have reported similar observations for rhythmic CAT and GPx activity, with maximal levels occurring during the dark phase in the mouse and rat brain. On the other hand, the location of enzymes activity peaks during the night-feeding-period, may suggest the influence of feeding cycle, and macro or micronutrients, such as proteins, carbohydrates, aspartate, glutamate or some vitamins, on those rhythms, as seen by Selmaoui and Thibault (2002), Manivasagam and Subramanian | 3,069,397 | 21239645 | 0 | 16 |
(2004) and Sivaperumal et al. (2007). Interestingly, the nocturnal peaks of CAT and GPx antioxidant activity seen in the hippocampus of our control rats would be in phase with the best time for performing learning and memory tests seen by Winocur and Hasher (2004) in young rats. On the other hand, daily variation in the expression and activity of the antioxidant systems, as well as the presence of E-box BMAL1:CLOCK responding sites found on the CAT and GPx promoters ( Figure 5), suggest those antioxidant enzymes would be under the endogenous clock control. Indeed, we found maximal CAT and GPx mRNA expression follow BMAL1 protein peak at the end-of-the-night/beginning-of-the-day in the control rats ( Figures 3A, 4A and 7, left panels) while the lowest levels of CAT and GPx expression occur after the negative regulator, PER1, protein peak ( Figures 3A and 4A, left panels, and 7, right panel). Recently, Hirayama et al. (2007) provided an attractive link between the regulation of the cellular reduction/oxidation (redox) state and the circadian control in the Z3 zebrafish embryonic cell line, which contains an independent, light-entrainable circadian oscillator. They showed that H 2 O 2 acts as the second messenger coupling photoreception to the zebrafish circadian clock, and that CAT shows oscillating expression and activity patterns, antiphasic to Per1, Per2 and Cry1, expression. As shown in Figures 3 and 7 for control animals, our findings are in agreement with their observations. Additionally, Hirayama et al. (2007) observed that overexpression of CAT results in a reduced lightdependent Cry1a and Per2 | 3,069,398 | 21239645 | 0 | 16 |
gene induction while inhibition of CAT function enhances lightmediated inducibility of these clock genes. These and our findings would implicate the existence of a mutual negative regulation between antioxidant enzymes and clock gene and protein expression. Differential effects of Vitamin A deficiency on daily oscillating patterns in the rat hippocampus Interestingly, we observed vitamin A deficiency exerts differential effects on the circadian expression and activity of CAT and GPx. On one hand, daily oscillations of CAT transcript, protein and activity are shallower in the vitamin A-deficient rats in comparison to control and vitamin A-refed groups (Figure 3, central panels). On the other hand, Vitamin A deficiency did not abolish or attenuate rhythmicity, but clearly phase-shifted day-night fluctuations of GPx mRNA expression and activity. Thus, a significant 8-h phase-shift of the GPx mRNA maximum and a 14-h phase-shift of GPx activity were observed in the hippocampus of vitamin A-deficient rats ( Figure 4A and C, central panels). In both cases, temporal changes in enzymatic activity follow changes in mRNA levels suggesting vitamin A-deficiency affects the circadian expression of CAT and GPx at the transcriptional level. Although others have tested and demonstrated the effects of nutritional factors, such as aspartate, glutamate or changes in feeding schedule (Selmaoui and Thibault, 2002;Manivasagam and Subramanian, 2004;Sivaperumal et al., 2007) on the circadian expression of antioxidant enzymes, this would be, at least at our knowledge, the first published report on the effects of vitamin A deficiency on the daily rhythmicity of CAT and GPx expression and activity and its putative impact on | 3,069,399 | 21239645 | 0 | 16 |
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