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Acquisition of internal models of motor tasks in children with autism
Gidley Larson, Jennifer C.
Bastian, Amy J.
Donchin, Opher
Shadmehr, Reza
Mostofsky, Stewart H.
Brain : a journal of neurology
2008;131(Pt 11):2894-2903.
Children with autism exhibit a host of motor disorders including poor coordination, poor tool use, and delayed learning of complex motor skills like riding a tricycle. Theory suggests that one of the crucial steps in motor learning is the ability to form internal models: to predict the sensory consequences of motor commands and learn from errors to improve performance on the next attempt. The cerebellum appears to be an important site for acquisition of internal models, and indeed the development of the cerebellum is abnormal in autism. Here, we examined autistic children on a range of tasks that required a change in the motor output in response to a change in the environment. We first considered a prism adaptation task in which the visual map of the environment was shifted. The children were asked to throw balls to visual targets with and without the prism goggles. We next considered a reaching task that required moving the handle of a novel tool (a robotic arm). The tool either imposed forces on the hand or displaced the cursor associated with the handle position. In all tasks, the children with autism adapted their motor output by forming a predictive internal model, as exhibited through after-effects. Surprisingly, the rates of acquisition and washout were indistinguishable from normally developing children. Therefore, the mechanisms of acquisition and adaptation of internal models in self-generated movements appeared normal in autism. Sparing of adaptation suggests that alternative mechanisms contribute to impaired motor skill development in autism. Furthermore, the findings may have therapeutic implications, highlighting a reliable mechanism by which children with autism can most effectively alter their behavior.
reach adaptation; prism adaptation; motor control; autism
Related Articles
Motor Learning Relies on Integrated Sensory Inputs in ADHD, but Over-Selectively on Proprioception in Autism Spectrum Conditions
Izawa, Jun
Pekny, Sarah E
Marko, Mollie K
Haswell, Courtney C
Shadmehr, Reza
Mostofsky, Stewart H
Autism Research
Lay Abstract
Children with autism spectrum disorder (ASD) show deficits in development of motor skills, in addition to core deficits in social skill development. In a previous study (Haswell et al., 2009) we found that children with autism show a key difference in how they learn motor actions, with a bias for relying on joint position rather than visual feedback; further, this pattern of motor learning predicted impaired motor, imitation and social abilities. We were interested in finding out whether this altered motor learning pattern was specific to autism. To do so, we examined children with Attention Deficit Hyperactivity Disorder (ADHD), who also show deficits in motor control. Children learned a novel movement and we measured rates of motor learning, generalization patterns of motor learning, and variability of motor speed during learning. We found children with ASD show a slower rate of learning and, consistent with previous findings, an altered pattern of generalization that was predictive of impaired motor, imitation, and social impairment. In contrast, children with ADHD showed a normal rate of learning and a normal pattern of generalization; instead, they (and they alone), showed excessive variability in movement speed. The findings suggest that there is a specific pattern of altered motor learning associated with autism.
Scientific Abstract
The brain builds an association between action and sensory feedback to predict the sensory consequence of self-generated motor commands. This internal model of action is central to our ability to adapt movements, and may also play a role in our ability to learn from observing others. Recently we reported that the spatial generalization patterns that accompany adaptation of reaching movements were distinct in children with Autism Spectrum Disorder (ASD) as compared to typically developing (TD) children. To test whether the generalization patterns are specific to ASD, here we compared the patterns of adaptation to those in children with Attention Deficit Hyperactivity Disorder (ADHD). Consistent with our previous observations, we found that in ASD the motor memory showed greater than normal generalization in proprioceptive coordinates compared with both TD children and children with ADHD; children with ASD also showed slower rates of adaptation compared with both control groups. Children with ADHD did not show this excessive generalization to the proprioceptive target, but did show excessive variability in the speed of movements with an increase in the exponential distribution of responses (τ) as compared with both TD children and children with ASD. The results suggest that slower rate of adaptation and anomalous bias towards proprioceptive feedback during motor learning is characteristic of autism; whereas increased variability in execution is characteristic of ADHD.
Related Articles
Evidence That the Pattern of Visuomotor Sequence Learning is Altered in Children With Autism
Gidley Larson, Jennifer C.
Mostofsky, Stewart H.
Autism research : official journal of the International Society for Autism Research
Motor deficits are commonly reported in autism, with one of the most consistent findings being impaired execution of skilled movements and gestures. Given the developmental nature of autism, it is possible that deficits in motor/procedural learning contribute to impaired acquisition of motor skills. Thus, careful examination of mechanisms underlying learning and memory may be critical to understanding the neural basis of autism. A previous study reported impaired motor learning in children with high-functioning autism (HFA); however, it is unclear whether the observed deficits in motor learning are due, in part, to impaired motor execution and whether these deficits are specific to autism. In order to examine these questions, 153 children (52 with HFA, 39 with attention-deficit/hyperactivity disorder (ADHD) and 62 typically developing (TD) children) participated in two independent experiments using a Rotary Pursuit task, with change in performance across blocks as a measure of learning. For both tasks, children with HFA demonstrated significantly less change in performance than did TD children, even when differences in motor execution were minimized. Differences in learning were not seen between ADHD and TD groups on either experiment. Analyses of the pattern of findings revealed that compared with both ADHD and TD children, children with HFA showed a similar degree of improvement in performance; however, they showed significantly less decrement in performance when presented with an alternate ("interference") pattern. The findings suggest that mechanisms underlying acquisition of novel movement patterns may differ in children with autism. These findings may help explain impaired skill development in children with autism and help to guide approaches for helping children learn novel motor, social and communicative skills.
procedural memory; declarative memory; cerebellum; visuomotor learning
Related Articles
Dynamics of Dual Prism Adaptation: Relating Novel Experimental Results to a Minimalistic Neural Model
Arévalo, Orlando
Bornschlegl, Mona A.
Eberhardt, Sven
Ernst, Udo
Pawelzik, Klaus
Fahle, Manfred
PLoS ONE
In everyday life, humans interact with a dynamic environment often requiring rapid adaptation of visual perception and motor control. In particular, new visuo–motor mappings must be learned while old skills have to be kept, such that after adaptation, subjects may be able to quickly change between two different modes of generating movements ('dual–adaptation'). A fundamental question is how the adaptation schedule determines the acquisition speed of new skills. Given a fixed number of movements in two different environments, will dual–adaptation be faster if switches ('phase changes') between the environments occur more frequently? We investigated the dynamics of dual–adaptation under different training schedules in a virtual pointing experiment. Surprisingly, we found that acquisition speed of dual visuo–motor mappings in a pointing task is largely independent of the number of phase changes. Next, we studied the neuronal mechanisms underlying this result and other key phenomena of dual–adaptation by relating model simulations to experimental data. We propose a simple and yet biologically plausible neural model consisting of a spatial mapping from an input layer to a pointing angle which is subjected to a global gain modulation. Adaptation is performed by reinforcement learning on the model parameters. Despite its simplicity, the model provides a unifying account for a broad range of experimental data: It quantitatively reproduced the learning rates in dual–adaptation experiments for both direct effect, i.e. adaptation to prisms, and aftereffect, i.e. behavior after removal of prisms, and their independence on the number of phase changes. Several other phenomena, e.g. initial pointing errors that are far smaller than the induced optical shift, were also captured. Moreover, the underlying mechanisms, a local adaptation of a spatial mapping and a global adaptation of a gain factor, explained asymmetric spatial transfer and generalization of prism adaptation, as observed in other experiments.
Related Articles
Coordination of precision grip in 2–6 years-old children with autism spectrum disorders compared to children developing typically and children with developmental disabilities
David, Fabian J.
Baranek, Grace T.
Wiesen, Chris
Miao, Adrienne F.
Thorpe, Deborah E.
Frontiers in Integrative Neuroscience
Impaired motor coordination is prevalent in children with Autism Spectrum Disorders (ASD) and affects adaptive skills. Little is known about the development of motor patterns in young children with ASD between 2 and 6 years of age. The purpose of the current study was threefold: (1) to describe developmental correlates of motor coordination in children with ASD, (2) to identify the extent to which motor coordination deficits are unique to ASD by using a control group of children with other developmental disabilities (DD), and (3) to determine the association between motor coordination variables and functional fine motor skills. Twenty-four children with ASD were compared to 30 children with typical development (TD) and 11 children with DD. A precision grip task was used to quantify and analyze motor coordination. The motor coordination variables were two temporal variables (grip to load force onset latency and time to peak grip force) and two force variables (grip force at onset of load force and peak grip force). Functional motor skills were assessed using the Fine Motor Age Equivalents of the Vineland Adaptive Behavior Scale and the Mullen Scales of Early Learning. Mixed regression models were used for all analyses. Children with ASD presented with significant motor coordination deficits only on the two temporal variables, and these variables differentiated children with ASD from the children with TD, but not from children with DD. Fine motor functional skills had no statistically significant associations with any of the motor coordination variables. These findings suggest that subtle problems in the timing of motor actions, possibly related to maturational delays in anticipatory feed-forward mechanisms, may underlie some motor deficits reported in children with ASD, but that these issues are not unique to this population. Further research is needed to investigate how children with ASD or DD compensate for motor control deficits to establish functional skills.
autism spectrum disorders; developmental delay; motor deficits; motor coordination; temporal motor coordination; precision grip; grip force; load force
Related Articles
Non-Specialist Psychosocial Interventions for Children and Adolescents with Intellectual Disability or Lower-Functioning Autism Spectrum Disorders: A Systematic Review
Reichow, Brian
Servili, Chiara
Yasamy, M. Taghi
Barbui, Corrado
Saxena, Shekhar
PLoS Medicine
In a systematic review, Brian Reichow and colleagues assess the evidence that non-specialist care providers in community settings can provide effective interventions for children and adolescents with intellectual disabilities or lower-functioning autism spectrum disorders.
Please see later in the article for the Editors' Summary
The development of effective treatments for use by non-specialists is listed among the top research priorities for improving the lives of people with mental illness worldwide. The purpose of this review is to appraise which interventions for children with intellectual disabilities or lower-functioning autism spectrum disorders delivered by non-specialist care providers in community settings produce benefits when compared to either a no-treatment control group or treatment-as-usual comparator.
Methods and Findings
We systematically searched electronic databases through 24 June 2013 to locate prospective controlled studies of psychosocial interventions delivered by non-specialist providers to children with intellectual disabilities or lower-functioning autism spectrum disorders. We screened 234 full papers, of which 34 articles describing 29 studies involving 1,305 participants were included. A majority of the studies included children exclusively with a diagnosis of lower-functioning autism spectrum disorders (15 of 29, 52%). Fifteen of twenty-nine studies (52%) were randomized controlled trials and just under half of all effect sizes (29 of 59, 49%) were greater than 0.50, of which 18 (62%) were statistically significant. For behavior analytic interventions, the best outcomes were shown for development and daily skills; cognitive rehabilitation, training, and support interventions were found to be most effective for improving developmental outcomes, and parent training interventions to be most effective for improving developmental, behavioral, and family outcomes. We also conducted additional subgroup analyses using harvest plots. Limitations include the studies' potential for performance bias and that few were conducted in lower- and middle-income countries.
The findings of this review support the delivery of psychosocial interventions by non-specialist providers to children who have intellectual disabilities or lower-functioning autism spectrum disorders. Given the scarcity of specialists in many low-resource settings, including many lower- and middle-income countries, these findings may provide guidance for scale-up efforts for improving outcomes for children with developmental disorders or lower-functioning autism spectrum disorders.
Protocol Registration
Please see later in the article for the Editors' Summary
Editors' Summary
Newborn babies are helpless, but over the first few years of life, they acquire motor (movement) skills, language (communication) skills, cognitive (thinking) skills, and social (interpersonal interaction) skills. Individual aspects of these skills are usually acquired at specific ages, but children with a development disorder such as an autism spectrum disorder (ASD) or intellectual disability (mental retardation) fail to reach these "milestones" because of impaired or delayed brain maturation. Autism, Asperger syndrome, and other ASDs (also called pervasive developmental disorders) affect about 1% of the UK and US populations and are characterized by abnormalities in interactions and communication with other people (reciprocal socio-communicative interactions; for example, some children with autism reject physical affection and fail to develop useful speech) and a restricted, stereotyped, repetitive repertoire of interests (for example, obsessive accumulation of facts about unusual topics). About half of individuals with an ASD also have an intellectual disability—a reduced overall level of intelligence characterized by impairment of the skills that are normally acquired during early life. Such individuals have what is called lower-functioning ASD.
Why Was This Study Done?
Most of the children affected by developmental disorders live in low- and middle-income countries where there are few services available to help them achieve their full potential and where little research has been done to identify the most effective treatments. The development of effective treatments for use by non-specialists (for example, teachers and parents) is necessary to improve the lives of people with mental illnesses worldwide, but particularly in resource-limited settings where psychiatrists, psychologists, and other specialists are scarce. In this systematic review, the researchers investigated which psychosocial interventions for children and adolescents with intellectual disabilities or lower-functioning ASDs delivered by non-specialist providers in community settings produce improvements in development, daily skills, school performance, behavior, or family outcomes when compared to usual care (the control condition). A systematic review identifies all the research on a given topic using predefined criteria; psychosocial interventions are defined as therapy, education, training, or support aimed at improving behavior, overall development, or specific life skills without the use of drugs.
What Did the Researchers Do and Find?
The researchers identified 29 controlled studies (investigations with an intervention group and a control group) that examined the effects of various psychosocial interventions delivered by non-specialist providers to children (under 18 years old) who had a lower-functioning ASD or intellectual disability. The researchers retrieved information on the participants, design and methods, findings, and intervention characteristics for each study, and calculated effect sizes—a measure of the effectiveness of a test intervention relative to a control intervention—for several outcomes for each intervention. Across the studies, three-quarters of the effect size estimates were positive, and nearly half were greater than 0.50; effect sizes of less than 0.2, 0.2–0.5, and greater than 0.5 indicate that an intervention has no, a small, or a medium-to-large effect, respectively. For behavior analytic interventions (which aim to improve socially significant behavior by systematically analyzing behavior), the largest effect sizes were seen for development and daily skills. Cognitive rehabilitation, training, and support (interventions that facilitates the relearning of lost or altered cognitive skills) produced good improvements in developmental outcomes such as standardized IQ tests in children aged 6–11 years old. Finally, parental training interventions (which teach parents how to provide therapy services for their child) had strong effects on developmental, behavioral, and family outcomes.
What Do These Findings Mean?
Because few of the studies included in this systematic review were undertaken in low- and middle-income countries, the review's findings may not be generalizable to children living in resource-limited settings. Moreover, other characteristics of the included studies may limit the accuracy of these findings. Nevertheless, these findings support the delivery of psychosocial interventions by non-specialist providers to children who have intellectual disabilities or a lower-functioning ASD, and indicate which interventions are likely to produce the largest improvements in developmental, behavioral, and family outcomes. Further studies are needed, particularly in low- and middle-income countries, to confirm these findings, but given that specialists are scarce in many resource-limited settings, these findings may help to inform the implementation of programs to improve outcomes for children with intellectual disabilities or lower-functioning ASDs in low- and middle-income countries.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001572.
This study is further discussed in a PLOS Medicine Perspective by Bello-Mojeed and Bakare
The US Centers for Disease Control and Prevention provides information (in English and Spanish) on developmental disabilities, including autism spectrum disorders and intellectual disability
The US National Institute of Mental Health also provides detailed information about autism spectrum disorders, including the publication "A Parent's Guide to Autism Spectrum Disorder"
Autism Speaks, a US non-profit organization, provides information about all aspects of autism spectrum disorders and includes information on the Autism Speaks Global Autism Public Health Initiative
The National Autistic Society, a UK charity, provides information about all aspects of autism spectrum disorders and includes personal stories about living with these conditions
The UK National Health Service Choices website has an interactive guide to child development and information about autism and Asperger syndrome, including personal stories, and about learning disabilities
The UK National Institute for Health and Care Excellence provides clinical guidelines for the management and support of children with autism spectrum disorders
The World Health Organization provides information on its Mental Health Gap Action Programme (mhGAP), which includes recommendations on the management of developmental disorders by non-specialist providers; the mhGAP Evidence Resource Center provides evidence reviews for parent skills training for management of children with intellectual disabilities and pervasive developmental disorders and interventions for management of children with intellectual disabilities
PROSPERO, an international prospective register of systematic reviews, provides more information about this systematic review
Related Articles
Individual Differences in the Real-Time Comprehension of Children with ASD
Venker, Courtney E.
Eernisse, Elizabeth R.
Saffran, Jenny R.
Weismer, Susan Ellis
Autism research : official journal of the International Society for Autism Research
Lay Abstract
Spoken language processing is related to language and cognitive skills in typically developing children, but very little is known about how children with autism spectrum disorders (ASD) comprehend words in real time. Studying this area is important because it may help us understand why many children with autism have delayed language comprehension. Thirty-four children with ASD (3–6 years old) participated in this study. They took part in a language comprehension task that involved looking at pictures on a screen and listening to questions about familiar nouns (e.g., Where's the shoe?). Children as a group understood the familiar words, but accuracy and processing speed varied considerably across children. The children who were more accurate were also faster to process the familiar words. Children's language processing accuracy was related to processing speed and language comprehension on a standardized test; nonverbal cognition did not explain additional information after accounting for these factors. Additionally, lexical processing accuracy at age 5½ was related to children's vocabulary comprehension three years earlier, at age 2½. Autism severity and years of maternal education were unrelated to language processing. Words typically acquired earlier in life were processed more quickly than words acquired later. These findings point to similarities in patterns of language development in typically developing children and children with ASD. Studying real-time comprehension in children with ASD may help us better understand mechanisms of language comprehension in this population. Future work may help explain why some children with ASD develop age-appropriate language skills, whereas others experience lasting deficits.
Scientific Abstract
Many children with autism spectrum disorders (ASD) demonstrate deficits in language comprehension, but little is known about how they process spoken language as it unfolds. Real-time lexical comprehension is associated with language and cognition in children without ASD, suggesting that this may also be the case for children with ASD. This study adopted an individual differences approach to characterizing real-time comprehension of familiar words in a group of 34 three- to six-year-olds with ASD. The looking-while-listening paradigm was employed; it measures online accuracy and latency through language-mediated eye movements and has limited task demands. On average, children demonstrated comprehension of the familiar words, but considerable variability emerged. Children with better accuracy were faster to process the familiar words. In combination, processing speed and comprehension on a standardized language assessment explained 63% of the variance in online accuracy. Online accuracy was not correlated with autism severity or maternal education, and nonverbal cognition did not explain unique variance. Notably, online accuracy at age 5½ was related to vocabulary comprehension three years earlier. The words typically learned earliest in life were processed most quickly. Consistent with a dimensional view of language abilities, these findings point to similarities in patterns of language acquisition in typically developing children and those with ASD. Overall, our results emphasize the value of examining individual differences in real-time language comprehension in this population. We propose that the looking-while-listening paradigm is a sensitive and valuable methodological tool that can be applied across many areas of autism research.
autism; comprehension; language processing; receptive vocabulary; eye-gaze methodology; individual differences
Related Articles
Advanced Paternal Age Is Associated with Impaired Neurocognitive Outcomes during Infancy and Childhood
Saha, Sukanta
Barnett, Adrian G
Foldi, Claire
Burne, Thomas H
Eyles, Darryl W
Buka, Stephen L
McGrath, John J
PLoS Medicine
Advanced paternal age (APA) is associated with an increased risk of neurodevelopmental disorders such as autism and schizophrenia, as well as with dyslexia and reduced intelligence. The aim of this study was to examine the relationship between paternal age and performance on neurocognitive measures during infancy and childhood.
Methods and Findings
A sample of singleton children (n = 33,437) was drawn from the US Collaborative Perinatal Project. The outcome measures were assessed at 8 mo, 4 y, and 7 y (Bayley scales, Stanford Binet Intelligence Scale, Graham-Ernhart Block Sort Test, Wechsler Intelligence Scale for Children, Wide Range Achievement Test). The main analyses examined the relationship between neurocognitive measures and paternal or maternal age when adjusted for potential confounding factors. Advanced paternal age showed significant associations with poorer scores on all of the neurocognitive measures apart from the Bayley Motor score. The findings were broadly consistent in direction and effect size at all three ages. In contrast, advanced maternal age was generally associated with better scores on these same measures.
The offspring of older fathers show subtle impairments on tests of neurocognitive ability during infancy and childhood. In light of secular trends related to delayed fatherhood, the clinical implications and the mechanisms underlying these findings warrant closer scrutiny.
Using a sample of children from the US Collaborative Perinatal Project, John McGrath and colleagues show that the offspring of older fathers exhibit subtle impairments on tests of neurocognitive ability during infancy and childhood.
Editors' Summary
Over the last few decades, changes in society in the developed world have made it increasingly common for couples to wait until their late thirties to have children. In 1993, 25% of live births within marriage in England and Wales were to fathers aged 35–54 years, but by 2003 it was 40%. It is well known that women's fertility declines with age and that older mothers are more likely to have children with disabilities such as Down's syndrome. In contrast, many men can father children throughout their lives, and little attention has been paid to the effects of older fatherhood.
More recent evidence shows that a man's age does affect both fertility and the child's health. "Advanced paternal age" has been linked to miscarriages, birth deformities, cancer, and specific behavioral problems such as autism or schizophrenia.
Rates of autism have increased in recent decades, but the cause is unknown. Studies of twins and families have suggested there may be a complex genetic basis, and it is suspected that damage to sperm, which can accumulate over a man's lifetime, may be responsible. A woman's eggs are formed largely while she is herself in the womb, but sperm-making cells divide throughout a man's lifetime, increasing the chance of mutations in sperm.
Why Was This Study Done?
There is good evidence linking specific disorders with older fathers, but the link between a father's age and a child's more general intelligence is not as clear. A recent study suggested a link between reduced intelligence and both very young and older fathers. The authors wanted to use this large dataset to test the idea that older fathers have children who do worse on tests of intelligence. They also wanted to re-examine others' findings using this same dataset that older mothers have more intelligent children.
What Did the Researchers Do and Find?
The researchers gathered no new data but reanalyzed data on children from the US Collaborative Perinatal Project (CPP), which had used a variety of tests given to children at ages 8 months, 4 years, and 7 years, to measure cognitive ability—the ability to think and reason, including concentration, memory, learning, understanding, speaking, and reading. Some tests included assessments of "motor skills"—physical co-ordination.
The CPP dataset holds information on children of 55,908 expectant mothers who attended 12 university-affiliated hospital clinics in the United States from 1959 to 1965. The researchers excluded premature babies and multiple births and chose one pregnancy at random for each eligible woman, to keep their analysis simpler. This approach reduced the number of children in their analysis to 33,437.
The researchers analyzed the data using two models. In one, they took into account physical factors such as the parents' ages. In the other, they also took into account social factors such as the parents' level of education and income, which are linked to intelligence. In addition, the authors grouped the children by their mother's age and, within each group, looked for a link between the lowest-scoring children and the age of their father.
The researchers found that children with older fathers had lower scores on all of the measures except one measure of motor skills. In contrast, children with older mothers had higher scores. They found that the older the father, the more likely was this result found.
What Do These Findings Mean?
This study is the first to show that children of older fathers perform less well in a range of tests when young, but cannot say whether those children catch up with their peers after the age of 7 years. Results may also be biased because information was more likely to be missing for children whose father's age was not recorded.
Previous researchers had proposed that children of older mothers may perform better in tests because they experience a more nurturing home environment. If this is the case, children of older fathers do not experience the same benefit.
However, further work needs to be done to confirm these findings. Especially in newer datasets, current trends to delay parenthood mean these findings have implications for individuals, couples, and policymakers. Individuals and couples need to be aware that the ages of both partners can affect their ability to have healthy children, though the risks for individual children are small. Policymakers should consider promoting awareness of the risks of delaying parenthood or introducing policies to encourage childbearing at an optimal age.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000040.
Mothers 35+ is a UK Web site with resources and information for older mothers, mothers-to-be, and would-be mothers, including information on the health implications of fathering a child late in life
The American Society for Reproductive Medicine published a Patient Information Booklet on Age and Fertility in 2003, which is available online; it contains a small section called "Fertility in the Aging Male," but otherwise focuses on women
The online encyclopedia Wikipedia has a short article on the "Paternal age effect" (note that Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
In 2005, the UK Office of National Statistics published a booklet entitled "Perpetual postponers? Women's, men's and couple's fertility intentions and subsequent fertility behaviour" looking at data from the British Household Panel Survey
Related Articles
Flexible Cognitive Strategies during Motor Learning
Taylor, Jordan A.
Ivry, Richard B.
PLoS Computational Biology
Visuomotor rotation tasks have proven to be a powerful tool to study adaptation of the motor system. While adaptation in such tasks is seemingly automatic and incremental, participants may gain knowledge of the perturbation and invoke a compensatory strategy. When provided with an explicit strategy to counteract a rotation, participants are initially very accurate, even without on-line feedback. Surprisingly, with further testing, the angle of their reaching movements drifts in the direction of the strategy, producing an increase in endpoint errors. This drift is attributed to the gradual adaptation of an internal model that operates independently from the strategy, even at the cost of task accuracy. Here we identify constraints that influence this process, allowing us to explore models of the interaction between strategic and implicit changes during visuomotor adaptation. When the adaptation phase was extended, participants eventually modified their strategy to offset the rise in endpoint errors. Moreover, when we removed visual markers that provided external landmarks to support a strategy, the degree of drift was sharply attenuated. These effects are accounted for by a setpoint state-space model in which a strategy is flexibly adjusted to offset performance errors arising from the implicit adaptation of an internal model. More generally, these results suggest that strategic processes may operate in many studies of visuomotor adaptation, with participants arriving at a synergy between a strategic plan and the effects of sensorimotor adaptation.
Author Summary
Motor learning has been modeled as an implicit process in which an error, signaling the difference between the predicted and actual outcome is used to modify a model of the actor-environment interaction. This process is assumed to operate automatically and implicitly. However, people can employ cognitive strategies to improve performance. It has recently been shown that when implicit and explicit processes are put in opposition, the operation of motor learning mechanisms will offset the advantages conferred by a strategy and eventually, performance deteriorates. We present a computational model of the interplay of these processes. A key insight of the model is that implicit and explicit learning mechanisms operate on different error signals. Consistent with previous models of sensorimotor adaptation, implicit learning is driven by an error reflecting the difference between the predicted and actual feedback for that movement. In contrast, explicit learning is driven by an error based on the difference between the feedback and target location of the movement, a signal that directly reflects task performance. Empirically, we demonstrate constraints on these two error signals. Taken together, the modeling and empirical results suggest that the benefits of a cognitive strategy may lie hidden in many motor learning tasks.
Related Articles
Altered Connectivity and Action Model Formation in Autism Is Autism
Mostofsky, Stewart H.
Ewen, Joshua B.
The Neuroscientist : a review journal bringing neurobiology, neurology and psychiatry
Internal action models refer to sensory-motor programs that form the brain basis for a wide range of skilled behavior and for understanding others' actions. Development of these action models, particularly those reliant on visual cues from the external world, depends on connectivity between distant brain regions. Studies of children with autism reveal anomalous patterns of motor learning and impaired execution of skilled motor gestures. These findings robustly correlate with measures of social and communicative function, suggesting that anomalous action model formation may contribute to impaired development of social and communicative (as well as motor) capacity in autism. Examination of the pattern of behavioral findings, as well as convergent data from neuroimaging techniques, further suggests that autism-associated action model formation may be related to abnormalities in neural connectivity, particularly decreased function of long-range connections. This line of study can lead to important advances in understanding the neural basis of autism and, more critically, can be used to guide effective therapies targeted at improving social, communicative, and motor function.
action models; autism; cerebral connectivity; EEG; motor function
Related Articles
Children with autism show specific handwriting impairments
Fuentes, Christina T.
Mostofsky, Stewart H.
Bastian, Amy J.
Handwriting skills, which are crucial for success in school, communication, and building children's self-esteem, have been observed to be poor in individuals with autism. Little information exists on the handwriting of children with autism, without delineation of specific features that can contribute to impairments. As a result, the specific aspects of handwriting in which individuals with autism demonstrate difficulty remain unknown.
A case-control study of handwriting samples from children with and without autism spectrum disorders (ASD) was performed using the Minnesota Handwriting Assessment. Samples were scored on an individual letter basis in 5 categories: legibility, form, alignment, size, and spacing. Subjects were also tested on the Wechsler Intelligence Scale for Children–IV and the Physical and Neurological Examination for Subtle (Motor) Signs.
We found that children with ASD do indeed show overall worse performance on a handwriting task than do age- and intelligence-matched controls. More specifically, children with ASD show worse quality of forming letters but do not show differences in their ability to correctly size, align, and space their letters. Within the ASD group, motor skills were significantly predictive of handwriting performance, whereas age, gender, IQ, and visuospatial abilities were not.
We addressed how different elements of handwriting contribute to impairments observed in children with autism. Our results suggest that training targeting letter formation, in combination with general training of fine motor control, may be the best direction for improving handwriting performance in children with autism.
= Autism Diagnostic Interview–Revised;
= Autism Diagnostic Observation Schedule–Generic;
= autism spectrum disorders;
= Diagnostic Interview for Children and Adolescents, 4th edition;
= Diagnostic and Statistical Manual of Mental Disorders, 4th edition;
= full-scale IQ;
= Physical and Neurological Examination for Subtle (Motor) Signs;
= Perceptual Reasoning Indices;
= Wechsler Intelligence Scale for Children–IV.
Related Articles
Decreased connectivity and cerebellar activity in autism during motor task performance
Mostofsky, Stewart H.
Powell, Stephanie K.
Simmonds, Daniel J.
Goldberg, Melissa C.
Caffo, Brian
Pekar, James J.
Although motor deficits are common in autism, the neural correlates underlying the disruption of even basic motor execution are unknown. Motor deficits may be some of the earliest identifiable signs of abnormal development and increased understanding of their neural underpinnings may provide insight into autism-associated differences in parallel systems critical for control of more complex behaviour necessary for social and communicative development. Functional magnetic resonance imaging was used to examine neural activation and connectivity during sequential, appositional finger tapping in 13 children, ages 8–12 years, with high-functioning autism (HFA) and 13 typically developing (TD), age- and sex-matched peers. Both groups showed expected primary activations in cortical and subcortical regions associated with motor execution [contralateral primary sensorimotor cortex, contralateral thalamus, ipsilateral cerebellum, supplementary motor area (SMA)]; however, the TD group showed greater activation in the ipsilateral anterior cerebellum, while the HFA group showed greater activation in the SMA. Although activation differences were limited to a subset of regions, children with HFA demonstrated diffusely decreased connectivity across the motor execution network relative to control children. The between-group dissociation of cerebral and cerebellar motor activation represents the first neuroimaging data of motor dysfunction in children with autism, providing insight into potentially abnormal circuits impacting development. Decreased cerebellar activation in the HFA group may reflect difficulty shifting motor execution from cortical regions associated with effortful control to regions associated with habitual execution. Additionally, diffusely decreased connectivity may reflect poor coordination within the circuit necessary for automating patterned motor behaviour. The findings might explain impairments in motor development in autism, as well as abnormal and delayed acquisition of gestures important for socialization and communication.
pediatric; movement; neuroimaging; motor learning; development; connections
Related Articles
Silent Synapses, LTP, and the Indirect Parallel-Fibre Pathway: Computational Consequences of Optimal Cerebellar Noise-Processing
Porrill, John
Dean, Paul
PLoS Computational Biology
Computational analysis of neural systems is at its most useful when it uncovers principles that provide a unified account of phenomena across multiple scales and levels of description. Here we analyse a widely used model of the cerebellar contribution to sensori-motor learning to demonstrate both that its response to intrinsic and sensor noise is optimal, and that the unexpected synaptic and behavioural consequences of this optimality can explain a wide range of experimental data. The response of the Marr-Albus adaptive-filter model of the cerebellar microcircuit to noise was examined in the context of vestibulo-ocular reflex calibration. We found that, when appropriately connected, an adaptive-filter model using the covariance learning rule to adjust the weights of synapses between parallel fibres and Purkinje cells learns weight values that are optimal given the relative amount of signal and noise carried by each parallel fibre. This optimality principle is consistent with data on the cerebellar role in smooth pursuit eye movements, and predicts that many synaptic weights must be very small, providing an explanation for the experimentally observed preponderance of silent synapses. Such a preponderance has in its turn two further consequences. First, an additional inhibitory pathway from parallel fibre to Purkinje cell is required if Purkinje cell activity is to be altered in either direction from a starting point of silent synapses. Second, cerebellar learning tasks must often proceed via LTP, rather than LTD as is widely assumed. Taken together, these considerations have profound behavioural consequences, including the optimal combination of sensori-motor information, and asymmetry and hysteresis of sensori-motor learning rates.
Author Summary
The cerebellum or "little brain" is a fist-sized structure located towards the rear of the brain, containing as many neurons as the rest of the brain combined, whose functions include learning to perform skilled motor tasks accurately and automatically. It is wired up into repeating microcircuits, sometimes referred to as cerebellar chips, in which learning alters the strength of the synapses between the parallel fibres, which carry input information, and the large Purkinje cell neurons, which produce outputs contributing to skilled movements. The cerebellar chip has a striking resemblance to a mathematical structure called an adaptive filter used by control engineers, and we have used this analogy to analyse its information-processing properties. We show that it learns synaptic strengths that minimise the errors in performance caused by unavoidable noise in sensors and cerebellar circuitry. Optimality principles of this kind have proved to be powerful tools for understanding complex systems. Here we show that optimality explains neuronal-level features of cerebellar learning such as the mysterious preponderance of "silent" synapses between parallel fibres and Purkinje cells and behavioural-level features such as the dependence of rate of learning of a motor skill on learning history.
Related Articles
Transient inhibition of the ERK pathway prevents cerebellar developmental defects and improves long-term motor functions in murine models of neurofibromatosis type 1
Kim, Edward
Wang, Yuan
Kim, Sun-Jung
Bornhorst, Miriam
Jecrois, Emmanuelle S
Anthony, Todd E
Wang, Chenran
Li, Yi E
Guan, Jun-Lin
Murphy, Geoffrey G
Zhu, Yuan
Individuals with neurofibromatosis type 1 (NF1) frequently exhibit cognitive and motor impairments and characteristics of autism. The cerebellum plays a critical role in motor control, cognition, and social interaction, suggesting that cerebellar defects likely contribute to NF1-associated neurodevelopmental disorders. Here we show that Nf1 inactivation during early, but not late stages of cerebellar development, disrupts neuronal lamination, which is partially caused by overproduction of glia and subsequent disruption of the Bergmann glia (BG) scaffold. Specific Nf1 inactivation in glutamatergic neuronal precursors causes premature differentiation of granule cell (GC) precursors and ectopic production of unipolar brush cells (UBCs), indirectly disrupting neuronal migration. Transient MEK inhibition during a neonatal window prevents cerebellar developmental defects and improves long-term motor performance of Nf1-deficient mice. This study reveals essential roles of Nf1 in GC/UBC migration by generating correct numbers of glia and controlling GC/UBC fate-specification/differentiation, identifying a therapeutic prevention strategy for multiple NF1-associcated developmental abnormalities.
DOI: http://dx.doi.org/10.7554/eLife.05151.001
eLife digest
Neurofibromatosis type 1 is a condition characterized by the growth of tumors along the nerves of the body. It is caused by mutations in a gene called NF1, which codes for a protein that normally works to inhibit the activity of another protein called Ras. In healthy cells, Ras is needed to stimulate the cells to grow and divide. However, if the Ras protein is not turned off at the right time or if it is activated at the wrong time, it can force cells to keep growing and dividing; this leads to the growth of tumors.
Along with being prone to developing cancer, individuals with neurofibromatosis type 1 also develop a range of neurodevelopmental disorders that alter their learning, motor skills and social interactions. Some also exhibit behaviors that are associated with autism. This led Kim, Wang et al. to investigate whether a region of the brain—called the cerebellum—that has recently been associated with autism is also affected in a mouse model of neurofibromatosis type 1.
The cerebellum is best known for its role in coordinating movement, although it also has functions in cognition, behavior and other processes. Ras is involved in the development of the cerebellum; and so Kim, Wang et al. asked whether the loss of the Nf1 gene from cells in the mouse cerebellum might cause the neurodevelopmental defects associated with neurofibromatosis type 1.
Loss of Nf1 during early (but not in late) development of the cerebellum disrupted the normal organization of the nerve cells (or neurons) into specific cell layers. These defects were caused, in part, by the over-growth of a type of supporting cell—called glia cells—at a specific developmental stage—that would normally form a scaffold to help neurons migrate to their correct position. Nf1 also controls the generation of the correct types of neurons in the right time and at right location during the early development of the cerebellum.
Next, Kim, Wang et al. treated newborn mice with a compound that inhibits Ras signaling via their mother's milk for 3 weeks. In mice with an inactive Nf1 gene, the treatment helped to prevent some defects in the cerebellum and the mice had improved motor coordination several months later. Whether this could form the basis of a preventative treatment for neurodevelopmental disorders associated with neurofibromatosis type 1 in humans remains a question for future work.
DOI: http://dx.doi.org/10.7554/eLife.05151.002
neurofibromatosis type 1; cerebellum; bergmann glial cells; granule cells; unipolar brush cells; tumor suppressor gene; mouse
Related Articles
Patterns of visual sensory and sensorimotor abnormalities in autism vary in relation to history of early language delay
Takarae, Yukari
Luna, Beatriz
Minshew, Nancy J.
Sweeney, John A.
Journal of the International Neuropsychological Society : JINS
Visual motion perception and pursuit eye movement deficits have been reported in autism. However, it is unclear whether these impairments are related to each other or toclinical symptoms of the disorder. High-functioning individuals with autism (41 with and 36 without delayed language acquisition) and 46 control subjects participated in the present study. All three subject groups were matched on chronological age and Full-Scale IQ. The autism group with delayed language acquisition had bilateral impairments on visual motion discrimination tasks, while the autism group without delay showed marginal impairments only in the left hemifield. Both autism groups showed difficulty tracking visual targets, but only the autism group without delayed language acquisition showed increased pursuit latencies and a failure to show the typical rightward directional advantage in pursuit. We observed correlations between performance on the visual perception and pursuit tasks in both autism groups. However, pursuit performance was correlated with manual motor skills only in the autism group with delayed language, suggesting that general sensorimotor or motor disturbances are a significant additional factor related to pursuit deficits in this subgroup. These findings suggest that there may be distinct neurocognitive phenotypes in autism associated with patterns of early language development.
autism phenotypes; visual motion perception; visual pursuit; population heterogeneity; language development; autism subtypes
Related Articles
Priors Engaged in Long-Latency Responses to Mechanical Perturbations Suggest a Rapid Update in State Estimation
Crevecoeur, Frédéric
Scott, Stephen H.
PLoS Computational Biology
In every motor task, our brain must handle external forces acting on the body. For example, riding a bike on cobblestones or skating on irregular surface requires us to appropriately respond to external perturbations. In these situations, motor predictions cannot help anticipate the motion of the body induced by external factors, and direct use of delayed sensory feedback will tend to generate instability. Here, we show that to solve this problem the motor system uses a rapid sensory prediction to correct the estimated state of the limb. We used a postural task with mechanical perturbations to address whether sensory predictions were engaged in upper-limb corrective movements. Subjects altered their initial motor response in ∼60 ms, depending on the expected perturbation profile, suggesting the use of an internal model, or prior, in this corrective process. Further, we found trial-to-trial changes in corrective responses indicating a rapid update of these perturbation priors. We used a computational model based on Kalman filtering to show that the response modulation was compatible with a rapid correction of the estimated state engaged in the feedback response. Such a process may allow us to handle external disturbances encountered in virtually every physical activity, which is likely an important feature of skilled motor behaviour.
Author Summary
It is commonly assumed that the brain uses internal estimates of the state of the body to adjust motor commands and perform successful movements. A problem arises when external disturbances deviate the limb from the ongoing task. In such cases, the estimated state of the body must be corrected based on sensory feedback. Because neural transmission delays can destabilize feedback control, an important challenge for motor systems is to correct the estimated state as quickly as possible. In this paper, we tested whether such a rapid correction is performed following mechanical loads applied to the upper limb. Our results indicate that long latency responses (∼50–100 ms) exhibit knowledge of the relationship between the delayed sensed joint displacement and the current state of the limb at the onset of the motor response. Importantly, this knowledge can be adjusted from one perturbation response to the next, should a distinct perturbation profile be experienced. These results suggest that a correction of state estimation is performed within the limb rapid-feedback pathways, allowing fast and stable feedback control.
Related Articles
Perceptual reasoning predicts handwriting impairments in adolescents with autism
Fuentes, Christina T.
Mostofsky, Stewart H.
Bastian, Amy J.
We have previously shown that children with autism spectrum disorder (ASD) have specific handwriting deficits consisting of poor form, and that these deficits are predicted by their motor abilities. It is not known whether the same handwriting impairments persist into adolescence and whether they remain linked to motor deficits.
A case-control study of handwriting samples from adolescents with and without ASD was performed using the Minnesota Handwriting Assessment. Samples were scored on an individual letter basis in 5 categories: legibility, form, alignment, size, and spacing. Subjects were also administered an intelligence test and the Physical and Neurological Examination for Subtle (Motor) Signs (PANESS).
We found that adolescents with ASD, like children, show overall worse performance on a handwriting task than do age- and intelligence-matched controls. Also comparable to children, adolescents with ASD showed motor impairments relative to controls. However, adolescents with ASD differ from children in that Perceptual Reasoning Indices were significantly predictive of handwriting performance whereas measures of motor skills were not.
Like children with ASD, adolescents with ASD have poor handwriting quality relative to controls. Despite still demonstrating motor impairments, in adolescents perceptual reasoning is the main predictor of handwriting performance, perhaps reflecting subjects' varied abilities to learn strategies to compensate for their motor impairments.
= autism spectrum disorder;
= Diagnostic and Statistical Manual of Mental Disorders, 4th edition;
= Physical and Neurological Examination for Subtle (Motor) Signs;
= Perceptual Reasoning Index;
= Wechsler Abbreviated Scale of Intelligence;
= Wechsler Intelligence Scale for Children IV.
Related Articles
Autism and attention-deficit/hyperactivity disorder among individuals with a family history of alcohol use disorders
Sundquist, Jan
Sundquist, Kristina
Ji, Jianguang
Recent studies suggest de novo mutations may involve the pathogenesis of autism and attention-deficit/hyperactivity disorder (ADHD). Based on the evidence that excessive alcohol consumption may be associated with an increased rate of de novo mutations in germ cells (sperms or eggs), we examine here whether the risks of autism and ADHD are increased among individuals with a family history of alcohol use disorders (AUDs). The standardized incidence ratios (SIRs) of autism and ADHD among individuals with a biological parental history of AUDs were 1.39 (95% CI 1.34–1.44) and 2.19 (95% CI 2.15–2.23), respectively, compared to individuals without an affected parent. Among offspring whose parents were diagnosed with AUDs before their birth, the corresponding risks were 1.46 (95% CI 1.36–1.58) and 2.70 (95% CI 2.59–2.81), respectively. Our study calls for extra surveillance for children with a family history of AUDs, and further studies examining the underlying mechanisms are needed.
DOI: http://dx.doi.org/10.7554/eLife.02917.001
eLife digest
Children learn to talk, manage their emotions, and control their behavior in a period when the brain is developing rapidly. The first signs of several developmental disorders, such as autism and attention-deficit/hyperactivity disorder (ADHD), may also emerge during this period. Children with autism may have difficulties with social interactions and communication, while those with attention-deficit/hyperactivity disorder may struggle to pay attention to a task and may be more active than other children.
Autism or ADHD are diagnosed based on the child's behavior because the underlying causes of the disorders are not well understood. Both genes and the environment have been linked to the conditions; and it was recently suggested that certain common genetic mutations are more common in children with ADHD or autism. However, as some of the mutations linked to autism are not found in the genes of the affected children's parents, it is likely that they occurred in either of the sperm or the egg cell from the parents.
Exposure to harmful substances in the environment can cause mutations in egg or sperm cells, or alter the expression of genes without changing the gene sequence. Excessive alcohol consumption is one environmental factor that can mutate genes or alter gene expression. Here, Sundquist et al. have looked to see if there is a relationship between a child having a parent with an alcohol use problem and the child's risk of developing autism or ADHD.
Examining national medical registries identified 24,157 people with autism and 49,348 with ADHD in Sweden between 1987 and 2010. Sundquist et al. discovered that autism and ADHD were more common in individuals who had a parent with a history of an alcohol use disorder than in those whose parents had no history of an alcohol use disorder. There was also an even greater risk of either condition if the parent had been diagnosed with an alcohol use problem before the birth of the child.
Adopted children who had a biological parent with an alcohol use disorder were at a greater risk of autism and ADHD than those whose adoptive parent had an alcohol use disorder. However, as very few adopted parents were diagnosed with an alcohol use problem, it is important to be cautious about drawing firm conclusions from this observation.
Sundquist et al. estimate that around 4% of autism cases and 11% of ADHD cases could be avoided if parents abstained from heavy alcohol consumption. Though these findings are consistent with parents with an alcohol use disorder being more likely to pass on mutations to their children, there are also other possible explanations. As such, further research examining the underlying cause is still needed.
DOI: http://dx.doi.org/10.7554/eLife.02917.002
autism; ADHD; alcohol use disorders; human
Related Articles
Gating of neural error signals during motor learning
Kimpo, Rhea R
Rinaldi, Jacob M
Kim, Christina K
Payne, Hannah L
Raymond, Jennifer L
Cerebellar climbing fiber activity encodes performance errors during many motor learning tasks, but the role of these error signals in learning has been controversial. We compared two motor learning paradigms that elicited equally robust putative error signals in the same climbing fibers: learned increases and decreases in the gain of the vestibulo-ocular reflex (VOR). During VOR-increase training, climbing fiber activity on one trial predicted changes in cerebellar output on the next trial, and optogenetic activation of climbing fibers to mimic their encoding of performance errors was sufficient to implant a motor memory. In contrast, during VOR-decrease training, there was no trial-by-trial correlation between climbing fiber activity and changes in cerebellar output, and climbing fiber activation did not induce VOR-decrease learning. Our data suggest that the ability of climbing fibers to induce plasticity can be dynamically gated in vivo, even under conditions where climbing fibers are robustly activated by performance errors.
DOI: http://dx.doi.org/10.7554/eLife.02076.001
eLife digest
The cerebellum (or 'little brain') is located underneath the cerebral hemispheres. Despite comprising around 10% of the brain's volume, the cerebellum contains roughly half of the brain's neurons. Many of the functions of the cerebellum are related to the control and fine-tuning of movement, and people whose cerebellum has been damaged have problems with balance and coordination, and with learning new motor skills.
One of the roles of the cerebellum is to control a reflex known as the vestibulo-ocular reflex, which enables us to keep our gaze fixed on an object as we turn our heads. The cerebellum relays information about head movements to the muscles that control the eyes, instructing the eyes to move in the opposite direction to the head. This keeps the image of the object we are looking at stable on the retina.
The vestibulo-ocular reflex is controlled by a circuit that includes Purkinje cells (which are the main output cells of the cerebellum) and climbing fibres (which originate in the brainstem). Any failure of the vestibulo-ocular reflex to fully compensate for head movements generates an error signal that activates the climbing fibres. These in turn modify the output of Purkinje cells, leading ultimately to adjustments in eye movements.
However, Kimpo et al. have now obtained evidence that Purkinje cells can modulate their response to the instructions they receive from climbing fibres. Monkeys sat in a rotating chair while a visual object they were trained to track with their eyes was moved to induce errors in the vestibulo-ocular reflex. When the object was moved so that a bigger reflexive eye movement was required to stabilize the image, the activation of the climbing fibres in response to the error led to a change in the response of the Purkinje cells, as expected. However, when a smaller reflexive eye movement was needed, the error-driven responses of the climbing fibres did not alter the responses of Purkinje cells. Similar results were obtained using pulses of light to artificially activate climbing fibres and thus simulate error signals.
The work of Kimpo et al. indicates that the cerebellum does not blindly follow the instructions it receives from the brainstem, but can instead modulate its responses to incoming information about performance errors. Further work is now required to identify factors that influence the responsiveness of the cerebellum: such information could ultimately be used to improve learning of motor skills and recovery from injury.
DOI: http://dx.doi.org/10.7554/eLife.02076.002
rhesus macaque; climbing fibers; cerebellum; motor learning; vestibulo-ocular reflex; supervised learning; mouse; other
Related Articles
The Impact of Augmented Information on Visuo-Motor Adaptation in Younger and Older Adults
Hegele, Mathias
Heuer, Herbert
PLoS ONE
Adjustment to a visuo-motor rotation is known to be affected by ageing. According to previous studies, the age-related differences primarily pertain to the use of strategic corrections and the generation of explicit knowledge on which strategic corrections are based, whereas the acquisition of an (implicit) internal model of the novel visuo-motor transformation is unaffected. The present study aimed to assess the impact of augmented information on the age-related variation of visuo-motor adjustments.
Methodology/Principal Findings
Participants performed aiming movements controlling a cursor on a computer screen. Visual feedback of direction of cursor motion was rotated 75° relative to the direction of hand motion. Participants had to adjust to this rotation in the presence and absence of an additional hand-movement target that explicitly depicted the input-output relations of the visuo-motor transformation. An extensive set of tests was employed in order to disentangle the contributions of different processes to visuo-motor adjustment. Results show that the augmented information failed to affect the age-related variations of explicit knowledge, adaptive shifts, and aftereffects in a substantial way, whereas it clearly affected initial direction errors during practice and proprioceptive realignment.
Contrary to expectations, older participants apparently made no use of the augmented information, whereas younger participants used the additional movement target to reduce initial direction errors early during practice. However, after a first block of trials errors increased, indicating a neglect of the augmented information, and only slowly declined thereafter. A hypothetical dual-task account of these findings is discussed. The use of the augmented information also led to a selective impairment of proprioceptive realignment in the younger group. The mere finding of proprioceptive realignment in adaptation to a visuo-motor rotation in a computer-controlled setup is noteworthy since visual and proprioceptive information pertain to different objects.
Related Articles
Discrimination Learning and Reversal of the Conditioned Eyeblink Reflex in a Rodent Model of Autism
Stanton, Mark E.
Peloso, Elizabeth
Brown, Kevin L.
Rodier, Patricia
Behavioural brain research
Offspring of rats exposed to valproic acid (VPA) on Gestational Day (GD) 12 have been advocated as a rodent model of autism because they show neuron loss in brainstem nuclei and the cerebellum resembling that seen in human autistic cases [20, 37]. Studies of autistic children have reported alterations in acquisition of classical eyeblink conditioning [40] and in reversal of instrumental discrimination learning [9]. Acquisition of discriminative eyeblink conditioning depends on known brainstem-cerebellar circuitry whereas reversal depends on interactions of this circuitry with the hippocampus and prefrontal cortex. In order to explore behavioral parallels of the VPA rodent model with human autism, the present study exposed pregnant Long-Evans rats to 600 mg/kg VPA on GD12 [cf. 37] and tested their offspring from PND26-31 on discriminative eyeblink conditioning and reversal. VPA rats showed faster eyeblink conditioning, consistent with studies in autistic children [40]. This suggests that previously reported parallels between human autism and the VPA rodent model with respect to injury to brainstem-cerebellar circuitry [37] are accompanied by behavioral parallels when a conditioning task engaging this circuitry is used. VPA rats also showed impaired reversal learning, but this likely reflected "carry-over" of enhanced conditioning during acquisition rather than a reversal learning deficit like that seen in human autism. Further studies of eyeblink conditioning in human autism and in various animal models may help to identify the etiology of this developmental disorder.
Eyeblink Conditioning; Gestational Valproate Exposure; Discrimination Reversal; Cerebellum; Hippocampus; Development
Related Articles
Adaptive Robotic Control Driven by a Versatile Spiking Cerebellar Network
Casellato, Claudia
Antonietti, Alberto
Garrido, Jesus A.
Carrillo, Richard R.
Luque, Niceto R.
Ros, Eduardo
Pedrocchi, Alessandra
D'Angelo, Egidio
PLoS ONE
The cerebellum is involved in a large number of different neural processes, especially in associative learning and in fine motor control. To develop a comprehensive theory of sensorimotor learning and control, it is crucial to determine the neural basis of coding and plasticity embedded into the cerebellar neural circuit and how they are translated into behavioral outcomes in learning paradigms. Learning has to be inferred from the interaction of an embodied system with its real environment, and the same cerebellar principles derived from cell physiology have to be able to drive a variety of tasks of different nature, calling for complex timing and movement patterns. We have coupled a realistic cerebellar spiking neural network (SNN) with a real robot and challenged it in multiple diverse sensorimotor tasks. Encoding and decoding strategies based on neuronal firing rates were applied. Adaptive motor control protocols with acquisition and extinction phases have been designed and tested, including an associative Pavlovian task (Eye blinking classical conditioning), a vestibulo-ocular task and a perturbed arm reaching task operating in closed-loop. The SNN processed in real-time mossy fiber inputs as arbitrary contextual signals, irrespective of whether they conveyed a tone, a vestibular stimulus or the position of a limb. A bidirectional long-term plasticity rule implemented at parallel fibers-Purkinje cell synapses modulated the output activity in the deep cerebellar nuclei. In all tasks, the neurorobot learned to adjust timing and gain of the motor responses by tuning its output discharge. It succeeded in reproducing how human biological systems acquire, extinguish and express knowledge of a noisy and changing world. By varying stimuli and perturbations patterns, real-time control robustness and generalizability were validated. The implicit spiking dynamics of the cerebellar model fulfill timing, prediction and learning functions.
Related Articles
Augmentation-related brain plasticity
Di Pino, Giovanni
Maravita, Angelo
Zollo, Loredana
Guglielmelli, Eugenio
Di Lazzaro, Vincenzo
Frontiers in Systems Neuroscience
Today, the anthropomorphism of the tools and the development of neural interfaces require reconsidering the concept of human-tools interaction in the framework of human augmentation. This review analyses the plastic process that the brain undergoes when it comes into contact with augmenting artificial sensors and effectors and, on the other hand, the changes that the use of external augmenting devices produces in the brain. Hitherto, few studies investigated the neural correlates of augmentation, but clues on it can be borrowed from logically-related paradigms: sensorimotor training, cognitive enhancement, cross-modal plasticity, sensorimotor functional substitution, use and embodiment of tools. Augmentation modifies function and structure of a number of areas, i.e., primary sensory cortices shape their receptive fields to become sensitive to novel inputs. Motor areas adapt the neuroprosthesis representation firing-rate to refine kinematics. As for normal motor outputs, the learning process recruits motor and premotor cortices and the acquisition of proficiency decreases attentional recruitment, focuses the activity on sensorimotor areas and increases the basal ganglia drive on the cortex. Augmentation deeply relies on the frontoparietal network. In particular, premotor cortex is involved in learning the control of an external effector and owns the tool motor representation, while the intraparietal sulcus extracts its visual features. In these areas, multisensory integration neurons enlarge their receptive fields to embody supernumerary limbs. For operating an anthropomorphic neuroprosthesis, the mirror system is required to understand the meaning of the action, the cerebellum for the formation of its internal model and the insula for its interoception. In conclusion, anthropomorphic sensorized devices can provide the critical sensory afferences to evolve the exploitation of tools through their embodiment, reshaping the body representation and the sense of the self.
supernumerary limbs; sensory substitution; cognitive enhancement; embodiment; brain machine interface (BMI); cross-modal plasticity; hand prostheses; sensorimotor abilities
Related Articles
Illusory Reversal of Causality between Touch and Vision has No Effect on Prism Adaptation Rate
Tanaka, Hirokazu
Homma, Kazuhiro
Imamizu, Hiroshi
Frontiers in Psychology
Learning, according to Oxford Dictionary, is "to gain knowledge or skill by studying, from experience, from being taught, etc." In order to learn from experience, the central nervous system has to decide what action leads to what consequence, and temporal perception plays a critical role in determining the causality between actions and consequences. In motor adaptation, causality between action and consequence is implicitly assumed so that a subject adapts to a new environment based on the consequence caused by her action. Adaptation to visual displacement induced by prisms is a prime example; the visual error signal associated with the motor output contributes to the recovery of accurate reaching, and a delayed feedback of visual error can decrease the adaptation rate. Subjective feeling of temporal order of action and consequence, however, can be modified or even reversed when her sense of simultaneity is manipulated with an artificially delayed feedback. Our previous study (Tanaka et al., 2011; Exp. Brain Res.) demonstrated that the rate of prism adaptation was unaffected when the subjective delay of visual feedback was shortened. This study asked whether subjects could adapt to prism adaptation and whether the rate of prism adaptation was affected when the subjective temporal order was illusory reversed. Adapting to additional 100 ms delay and its sudden removal caused a positive shift of point of simultaneity in a temporal order judgment experiment, indicating an illusory reversal of action and consequence. We found that, even in this case, the subjects were able to adapt to prism displacement with the learning rate that was statistically indistinguishable to that without temporal adaptation. This result provides further evidence to the dissociation between conscious temporal perception and motor adaptation.
motor adaptation; subjective simultaneity; physical simultaneity; temporal adaptation; spatial adaptation; illusory reversal
Related Articles
Cerebellar Contributions to Reach Adaptation and Learning Sensory Consequences of Action
Izawa, Jun
Criscimagna-Hemminger, Sarah E.
Shadmehr, Reza
The Journal of Neuroscience
When we use a novel tool, the motor commands may not produce the expected outcome. In healthy individuals, with practice the brain learns to alter the motor commands. This change depends critically on the cerebellum as damage to this structure impairs adaptation. However, it is unclear precisely what the cerebellum contributes to the process of adaptation in human motor learning. Is the cerebellum crucial for learning to associate motor commands with novel sensory consequences, called forward model, or is the cerebellum important for learning to associate sensory goals with novel motor commands, called inverse model? Here, we compared performance of cerebellar patients and healthy controls in a reaching task with a gradual perturbation schedule. This schedule allowed both groups to adapt their motor commands. Following training, we measured two kinds of behavior: in one case people were presented with reach targets near the direction in which they had trained. The resulting generalization patterns of patients and controls were similar, suggesting comparable inverse models. In another case, they reached without a target and reported the location of their hand. In controls the pattern of change in reported hand location was consistent with simulation results of a forward model that had learned to associate motor commands with new sensory consequences. In patients, this change was significantly smaller. Therefore, in our sample of patients we observed that while adaptation of motor commands can take place despite cerebellar damage, cerebellar integrity appears critical for learning to predict visual sensory consequences of motor commands.
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text:
Somehow jpgs on my photo blog sites* are no longer displaying FOR ME - they seem to still work the same as always for others.
- http://montereyscenics.posterous.com/ and http://iceagetrail.posterous.com/
I don't recall tweaking any settings on my computer that would cause this to happen. Is it a browser setting, maybe? But, I'm not seeing any difference in general, just on MY sites. But, again, others can still see the images, so I'm confused as to how this happened (and more importantly, how to change it back/fix it).
If I opt to download one of my images from the iceagetrail site, McAfee Site Advisor intercepts the attempt to download the file with:
Are you sure you want to go there?
http://getfile4.posterous.com/getfile/files.poster... may be risky to visit.
Why were you redirected to this page? When we visited this site, we found it exhibited one or more risky behaviors. ~~~~~~~~~~~~~~~~~~~~~~~~~~
When I opt to go ahead anyway, I get to a "Panda Cloud Antivirus Safe Search Protection" page:
The page has been blocked as it contains malware or exploits
The Web page you are trying to access contains malware and exploits that could infect your computer. We advise you not to continue visiting this page. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When I opt to go ahead anyway, I get
The website declined to show this webpage
Most likely causes: •This website requires you to log in.
What you can try:
Go back to the previous page.
More information More information
This error (HTTP 403 Forbidden) means that Internet Explorer was able to connect to the website, but it does not have permission to view the webpage. For more information about HTTP errors, see Help. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
So...now I'm more confused and discombobulated than ever...McAfee and/or Panda are preventing me from seeing my own site? (I can login and get to the page/site, but the images are not displayed)
jpg settings photo

subset: commoncrawl


text:
The Shield appeared on 'Piper's Pit'
As the WWE Universe knows, just when you think you know the answers, "Rowdy" Roddy Piper changes the questions. Even The Shield, despite their insistence otherwise, isn't immune from Hot Rod's mind games, as the WWE Hall of Famer stirred The Hounds of Justice into a froth by bringing up their recent string of losses to CM Punk on "Piper's Pit". Even Roman Reigns – the one Hound yet to fight Punk one-on-one – wasn't in the mood to take Piper's guff, and the WWE Hall of Famer's line of questioning seemed to set him up for a very immediate beating. That is, until Punk himself – with The New Age Outlaws in tow – sprinted to Piper's aid and sent The Shield scrambling.
Roman Reigns def. CM Punk
Believe this: There is, as it turns out, one member of The Shield who can defeat CM Punk, and his name is Roman Reigns. After weeks of torment at the hands of Punk, The Hounds of Justice's resident Doberman backed up his group's fierce rhetoric and feasted upon The Best in the World … although the favor was certainly repaid at the end of the night.
Even with The New Age Outlaws backing him up at ringside, Punk was forced into an uphill battle by Reigns, who slowly wore him down over the course of the match. Reigns' repeated targeting of Punk's banged-up ribs kept The Second City Saint in neutral for a long time, though Punk found separation by countering Regins' Superman punch with a kick to the head that brought the match back to an even level. The two Superstars threw signature maneuvers back and forth until Ambrose provided a timely distraction and Reigns pounced with a spear that finally put Punk down for the win.
The Shield was hardly out of the woods yet, though, as none other than Jake "The Snake" Roberts made his way to the ring and – with an assist from Punk and The Outlaws – unleashed his trademark pet serpent all over a beaten Ambrose while Rollins & Reigns made their escape. Now that's old-school.
HQ Digitals || HQ Screencaptures
In the first SmackDown of 2014, The Best in the World CM Punk and the high-octane Usos reigned supreme over a Shield trio who couldn't seem to get on the same page. Plus, WWE Tag Team Champions Cody Rhodes & Goldust withstood the formidable challenge of The Wyatt Family and Bray Wyatt himself delivered a creepy message about Daniel Bryan joining the fold.
At the opening of SmackDown, United States Champion Dean Ambrose addressed recent speculation about possible dissention in the ranks of The Hounds of Justice – informing CM Punk, in particular, that he couldn't divide and conquer them. Roman Reigns added that there was no weak link to divide and Seth Rollins said that any setbacks they had were temporary, since in the end, they would do what they do best – come together and dominate.
Ambrose then joined the SmackDown announce team as his cohorts battled The Usos. However, when it looked as if Jimmy & Jey might close the door on their black-clad adversaries, Ambrose intervened – bringing an abrupt end to the match by disqualification.
The Shield's post-match attack would be thwarted when The Straight Edge Superstar emerged to even the odds and helped to send the Hounds packing. SmackDown General Manager Vickie Guerrero would then create a huge SmackDown main event showdown on the WWE App: Ambrose, Reigns & Rollins vs. Punk & the Samoan warriors!
CM Punk & The Usos def. The Shield
With an absence of teamwork and apparent communication problems between The Shield in the final moments of a huge SmackDown main event, The Usos helped CM Punk take down Seth Rollins and Roman Reigns. This cleared the way for The Best in the World to overcome Dean Ambrose with the GTS for the victory.


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Speed Flower
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A Speed Flower is a type of flower found in Super Paper Mario. If one of the four heroes (Mario, Luigi, Bowser, Princess Peach) pick it up, everything will speed up for a short period of time. Within that time, points and coins the heroes would earn will be tripled.
The Slow Flower is the blue-colored opposite of the Speed Flower, and makes everything go slower.


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UT graduate, Navy pilot and astronaut, Barry Wilmore spoke to students and faculty on Sept. 11 about his recent stint aboard the International Space Station.Read more
SGA Profile: Seth, Leala, Willie campaign wants to put students first
SGA Profile: Get to know Seth Watkins and Willie Kemp of the Seth, Leala, Willie SGA campaign.Read more
Vols defeat Vanderbilt, 67-61, advance to play Arkansas in SEC tournament
Tennessee trailed Vanderbilt 59-47 with just over six minutes remaining in Thursday's SEC tournament game. With a slew of three-pointers, the Vols finished the game on a 20-2 run, defeating Vanderbilt 67-61.Read more
Five date ideas to win over your valentine
Plan a special night for your valentine in Knoxville. Here is a list of five romantic ideas that will be sure to swoon your sweetheart.Read more
Student Representative resigns from position
UT's Board of Trustees student representative resigned from his position on Friday, Nov. 21.Read more
Former death row inmate speaks out against death penalty
Monday, Nov., 17, former death row inmate, Ray Krone spoke out against the death penalty. Krone spent ten years in prison, nearly three of those years on death row. The presentation was hosted by Young Americans for Liberty at the University of Tennessee int he Shiloh Room. [caption id="attachment_13739" align="alignleft" width="300"] Photo by Carson McCullough.[/caption]…Read more


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This is a three day old article in the Independent but it raises new issues about the nascent candidacy of UKIP's Diane James. Some highlights:
One said: "Maria Hutchings is the Conservative candidate but her rhetoric on Europe and other issues makes her sound like Ukip. Diane James comes across as more centrist and sensible. She looks and sounds like a Tory. It is possible she could win this."
You can count on a UKIP candidate being anti-EU and pro-liberty (although UKIP has many social conservatives that are skeptical on gay marriage; UKIP is for civil unions for gays) and the party has campaigned hard for the seat! An internal poll shows with those who did not know who they will vote for not allocated based on the 2010 General Election, UKIP is up to 25%, only six behind LibDems and one percent behind the Tory candidate! It is obvious the Liberal Democrats don't get it:
Lord Oakeshott, the Lib Dem former Treasury spokesman, said: "Conservative anti-immigration and anti-European dog-whistling is a gift to Ukip."
Obviously Lord Oakeshott is unconcerned about British jobs or sovereignty. UKIP is an non-racist libertarian political party dedicated to restoring the EU to the original laudatory intent of the Common Market – a free trade zone dedicated to democracy – not an elitist superempire wannabe.
Finally, victory for UKIP would be dramatic:
Such a result would send shockwaves through the Conservative and Liberal Democrat parties, which began the campaign planning a two-way fight between the coalition partners.
The UKIP win is the best way to bring about the EU referendum that is needed immediately.


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The Senate Plan to Tackle Homelessness in California
Climate change is a global challenge and the California example will be critical to the efforts of world leaders moving forward.
With Governor Jerry Brown's recent signature of all ten bills in the Immigrants Shape California legislative package, California continues to value and protect its immigrant residents and provide economic opportunity and justice for all their families.
From the first day of session, Senate Democrats pledged to build on our state's progress and give more Californians — especially middle-class families and underserved communties — greater access to the California Dream. And that's exactly what they have done.
How does the new vaccine law work?
Meet our members
Senate Spotlight
Drought Information
Register to Vote


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BIG NEWS: INTRODUCING SHANKMAN|HONIG!2 years ago
In late 2007, when I launched my last company, HARO, I wanted to disrupt how journalists found their sources, and more importantly, how companies were able to get publicity. It seemed to me that the old ways of doing things (either paying for publicity, or journalists frantically calling sources to beat their deadline) was ripe for a change. As it turned out, I was right, and HARO blew up beyond my wildest dreams, to be acquired just a few short years later.
Well, it's time for my next big disruption, and I'm thrilled to be able to announce it here.
In the past 30 or so years, we've watched the downfall and eventual demise of customer service. For those old enough to remember, when you brought your car to the gas station in the 50s, four attendants, (in clean uniforms, even!) would rush out - One would check your oil, one your tires, one your windshield wiper fluid, and one would actually pump your gas. Amazing! Good luck getting that now, in our "self-serve or pay more" world.
Let's face it - Customer service in this country has gone to complete hell, and sadly, we accept that as normal. We go to a fast food restaurant and expect to be treated like crap. Our dry-cleaning isn't ready when they say it will be, and come on, let's not even get STARTED on airlines or wireless providers. Companies don't bother giving better customer service because they see it as a waste of money. "Pennywise, pound foolish," seems to be the motto, as companies focus short-sightedly on "this quarter's revenues," and not "long term effect."
Here's what companies big and small aren't getting though - The game has changed. You got screwed by a company in the 1980s? What were you going to do? Write a letter to the editor of your local paper? Tell a few friends? That was it. I challenge you to find ONE PERSON today who doesn't have a camera in their phone, connected to the heartbeat of the world via multiple channels in real time.
We're a new economy. We're a conversation economy. Your customer service strategy can no longer be "we'll wait for someone to complain on Twitter then we'll placate them." It has to be about your company having stellar customer service in the real world that's so amazing, it's talked about by every customer you have. And we're not talking "oh, we'll upgrade everyone on every flight to first class," or some other irrational plea for attention. No. We're talking about teaching you how to run your business in such a way that terrific customer service is the norm. Do that, and your customers return with friends. Do that, and your employees never leave. Do that, and you're light years above the rest.
With that, I'm proud to say that I'm launching a new customer service consultancy with my good friend and colleague Rachel Honig, called, simply enough, Shankman|Honig. Our mission is to do one thing: Teach companies big and small how to improve their customer service with an end result of higher revenues, increased profits, and elevated brand awareness.
We haven't even launched yet, and we've got a handful of clients in our stable, including Westfield Terminal C, (the company that manages the giant mall that is Terminal C at Newark Airport,) Steiner Sports, and several others.
If the last ten years were about social media, the next twenty are going to be about customer service, and only companies who truly embrace that will remain standing. Want proof? It costs five times more to acquire a new customer than keep an existing one, and 89% of customers are likely to leave a brand after a single unresolved bad experience. That tells you to get it right the first time.
Want to learn more? Think we can help you? Just want to chat? Go for a run? Skydive? (Just because it's a new company doesn't mean my personality has changed...) Then shoot me an email, leave a comment, visit the new company, or simply click "contact" above.
The new economy is going to be based on Customer Service, on the art of "helping" without "selling." If your help rocks, the sales will come. Or, to put it another way, if you focus on providing exceptional service to the customers you have, you'll easily get the customers you want.
With that said... How can we help you today?
TL:DR: My next venture is launching a new consultancy designed to reinvent customer service.