petersen et al . reported that dyspnea 
 causes multiple symptoms such as active breathing , heavy breathing , and chest tightness2 . furthermore , dyspnea is affected by the 
 surrounding environment , experiential background , and physical condition of the individual , 
 as well as by their psychological characteristics and previous experiences . generally , 
 certain drugs administered for dyspnea induce sedation , pain relief , and reduced respiratory 
 motor output in patients with lung cancer3 . however , excessive use of these drugs can also have negative health 
 effects , such as an increase in activity avoidance , which results in deconditioning4 . recent studies have used functional brain imaging equipment to understand the relationship 
 between brain function and dyspnea5 , 6 . according to these reports , dyspnea is 
 closely associated with the cerebral limbic system , specifically the insula and anterior 
 cingulate cortex7,8,9 . two major pathways may be 
 involved in the processing of respiratory sensations on their way to the cortex10 , 11 . the first pathway arises predominantly from respiratory muscle 
 afferents , which are relayed to the brainstem medulla , and project to the ventroposterior 
 thalamus , where thalamocortical projections ascend to the primary and secondary 
 somatosensory cortices . these structures may process the sensory or intensity aspects of 
 dyspnea along with other interoceptive sensations . the second pathway includes mainly vagal 
 afferents from the lungs and airways , which are relayed to the brainstem medulla . brainstem 
 projections then ascend to the amygdala and medial dorsal areas of the thalamus , where they 
 project to the insula and cingulate cortex . this predominantly limbic pathway might also 
 include the hippocampus , operculum , putamen , and other prefrontal areas , and might be 
 associated with the affective components of the experience of breathlessness . however , 
 higashimoto et al . showed that cortical activation in the prefrontal area , as indicated by 
 increased oxygenated hemoglobin ( oxy - hb ) concentrations , corresponds to the level of 
 dyspnea , and that the change in oxy - hb concentration in patients with chronic obstructive 
 pulmonary disease did not differ from that in controls12 . dyspnea is influenced not only by exercise load , but also by 
 unpleasant emotions caused by affective photographic images13,14,15,16 . these image studies 
 suggested that to better understand dyspnea , we need to examine brain activity while 
 subjects anticipate effort triggered by prior dyspnea experiences . in this study , we monitored two potential brain mechanisms of dyspnea awareness : cortical 
 activity ( as mirrored by hemodynamic responses ) was measured with multichannel functional 
 near - infrared spectroscopy ( fnirs ) ; and sympathetic nerve activity ( as mirrored by rr 
 distance , a reflector of heart rate variation ) was measured with active tracers . our 
 findings indicate that dyspnea is affected by previous dyspnea experiences and is closely 
 associated with activity in the right medial prefrontal cortex ( rmpfc ) . fifteen healthy volunteers with a mean age of 25.0  3.0  years and a mean maximal peak 
 inspiratory pressure ( pi ) of 78.0  26.4 cmh2o ( determined by microspirometry ) 
 participated in this study . normal baseline lung 
 function was confirmed by microspirometry ( hi-801 , nihonkoden , tokyo , japan ) . the breathing resistive intensity method was employed to evoke dyspnea by increasing the 
 effort involved and discomfort experienced during breathing . subjects breathed via a 
 mouthpiece connected to the resistive breathing valve of a threshold imt device ( philips 
 respironics , tokyo , japan ) . using microspirometry , the maximum pi of each subject was 
 determined to calculate the results for three different levels of resistance : pleasant ( 7 
 mmhg ; minimum pressure ) , neutral ( the pressure was 15% that of the maximum pi ) , and 
 unpleasant ( the pressure was 30% that of the maximum pi ) . the effect of pi at 30% of the 
 maximum intensity was previously measured using normal subjects17 . therefore , we confirmed the effect of pi at 30% of the 
 maximum on brain activity18 . we used fnirs ( foire3000 , shimadzu , kyoto , japan ) to measure the relative changes in 
 concentrations of oxy - hb over time , through at multiple channels , with a 0.1-s time 
 resolution , and at two wavelengths of fnirs light ( 780  nm and 830  nm)19 . data analyses were based on effect size ( mean rest oxy - hb 
  mean task oxy - hb / standard deviation [ sd ] of rest oxy - hb ) . oxygen consumption has various 
 effects on cerebral blood flow , cerebral blood volume , and the metabolic rate during 
 cortical activity20 . based on the oxy - hb 
 values , we determined the cortical areas that were responsive to our task21 . we evaluated oxy - hb changes relative to 
 individual baseline values obtained at the start of the measurement period , since the 
 baseline oxy - hb can vary a great deal across subjects . because the precise optical path lengths were unknown , the unit of measurement was 
 determined by the value that multiplied molar concentration by length ( mmmm ) . the subjects 
 wore a cap that covered the entire head with the electrode array arranged so that it covered 
 the prefrontal area ( 5  6 array ; 15 incident and 15 detection optical fibers ) . each pair of adjacent incident and 
 detection fibers defined a single measurement channel , which enabled us to simultaneously 
 measure the time courses of oxy - hb across the 49 measurement channels . the locations of 
 the 1020 cortical projection points , labeled according to the standard montreal 
 neurological institute template , were estimated using the statistical parametric mapping 
 ( spm ) software . based on these estimations , it was determined that the regions of interest 
 were the medial and dorsal prefrontal cortex . a previous study showed that blood pressure ( bp ) does not change during submaximal exercise 
 ( 150  w)22 . however , other studies using 
 multiple regression analysis have shown that oxy - hb affects bp and co223,24,25 . therefore , we could not ignore the 
 effects of bp and co2 during our task . the first peaks of rr waves on the electrocardiogram were detected , and the rr was measured 
 with an active tracer ( ac-301a , gms , tokyo , japan ) . the rr data were analyzed using the 
 maximum - entropy method with high resolution ( memcalc ; gms ) . for real - time analysis of hrv , 
 the rr data were derived using online computer analysis with 30-ms sampling intervals . the 
 power of the rr ( ms ) was determined for the low frequency ( lf ; 0.0040.15  hz ) 
 and high frequency ( hf ; 0.150.5  hz ) bands . sympathetic nerve activity was estimated by 
 calculating the lf / hf of 9 series using the memcalc program . thus , we analyzed hrv as the 
 lf / hf of task time divided by the lf / hf of rest time . prior to testing , subjects were familiarized with the measurement protocol and apparatus , 
 and interviewed to make sure they understood the test . thirty minutes after the interview , 
 subjects underwent 9 blocks of fnirs and rr measurements during the recorded trials . after 
 following standardized instructions and positioning of the fnirs , a sensor net with three 
 electrodes was placed on the chest , and a nose clip was fitted . each experimental trial consisted of viewing images for 20  s , breathing resistance 
 measurements for 30  s , and selective borg scale assessments for 20 s. volunteers viewed a 
 random combination of custom - made photographs showing pleasant , neutral , or unpleasant 
 images . the subjects were instructed to anticipate the breathing resistance that 
 corresponded to the affective value of the photograph . after viewing each image , the 
 subjects were randomly subjected to a breathing resistance that was identical to , easier 
 than , or harder than that shown in the image ; the image and resistance were identical 33% of 
 the time and discordant 66% of the time . the breathing resistances ( 7 mmhg , 15% of pi max , 
 30% of pi max ) were induced using the threshold imt device . brain and sympathetic nervous 
 system activity were subsequently assessed in three ways : the borg scale was used to assess 
 the psychophysical response , tracers were used to measure sympathetic nervous system 
 activity , and fnirs was used to index brain activity . the dyspnea intensity perceived by 
 subjects was measured using the borg scale , which is generally known to most medical 
 staff26 . the results are reported as the mean  sd . the breathing intensities were analyzed as 
 dependent variables with two - way repeated - measures analyses of variance ( anovas ) . bonferroni - corrected , univariate , pairwise comparisons were calculated for further 
 exploration of the factors contributing to the main effect . oxy - hb and lf / hf ratios were 
 analyzed using friedman s test and wilcoxon s signed - rank test . correlation analyses of the 
 borg scale measurements and oxy - hb values were performed using spearman s correlation 
 coefficient . we also analyzed the oxygen saturation and bp , which were measured before and 
 after the experiment , to evaluate the effects of the peripheral circulatory state on oxy - hb . all analyses were conducted using spss 20.0 software ( spss , japan , inc . , tokyo , japan ) . the intensity of subjects dyspnea was increased by the anticipation triggered by prior 
 experience of dyspnea . perceptions of 
 increased intensity were produced when the subjects viewed a pleasant image compared to when 
 they viewed an unpleasant image at the same intensity of 30% pi ( p < 0.01 , table 1table 1.the intensity of subjects dyspnea as assessed on the borg scale under the 9 
 conditionsimagepleasantneutralunpleasantbreath resistancepleasant ( 7 mmhg)91.7692.26101.99neutral ( 15% of pi max)111.40121.95121.45unpleasant ( 30% of pi max)131.62131.36121.22<0.01 for the comparison where the anticipation of the pleasant image 
 was stronger than that for the unpleasant image ) . the average increase in perceived intensity at 30% pi when viewing a 
 pleasant image was 6.5% ( range : 0.014.3% ) , with all 15 subjects exhibiting increased 
 dyspnea intensities following a decreased expectation of dyspnea . < 0.01 for the comparison where the anticipation of the pleasant image 
 was stronger than that for the unpleasant image during the fnirs acquisition session , oxy - hb values in the dorsolateral prefrontal cortex 
 ( dlpfc ) increased during the expectation phase when viewing the unpleasant images ( p < 
 0.05 , table 2table 2.comparison of effect size in the regions of interest ( roi ) under the three 
 conditions with 30% pi max intensityimagepleasantneutralunpleasantleftrightleftrightleftrightmpfc2.683.300.333.052.102.780.943.141.812.582.23.47dlpfc1.872.251.412.420.232.370.922.470.492.640.142.82breath resistancempfc3.373.610.453.261.993.141.084.191.793.111.333.80dlpfc2.942.943.283.312.312.212.392.562.442.551.942.04<0.05 for the comparison where the anticipation of the unpleasant 
 image was stronger than that of the pleasant image . < 0.01 for the 
 comparison where the anticipation of the pleasant image was stronger than that of the 
 unpleasant image ) . oxy - hb values in the subjects rmpfc increased in response to experiencing 
 an unpleasant intensity when viewing a pleasant image ( p < 0.01 , table 2 ) . moreover , rmpfc activation was significantly related to 
 the intensity of perceived dyspnea ( r = 0.6 , p < 0.01 ) . however , neither the sympathetic 
 nerve activity nor peripheral circulation significantly changed during changes in the 
 perceived dyspnea intensity . these results suggest that activity in the rmpfc was increased 
 by the prior dyspnea experiences . the brain activity corresponded to the degree of dyspnea 
 when subjects experienced an unpleasant intensity after viewing a pleasant image . < 0.05 for the comparison where the anticipation of the unpleasant 
 image was stronger than that of the pleasant image . < 0.01 for the 
 comparison where the anticipation of the pleasant image was stronger than that of the 
 unpleasant image this study examined the influence of expectations on cortical activation and dyspnea using 
 fnirs and an active tracer in healthy subjects . the results show that cortical activation in 
 the rmpfc was associated with increased oxy - hb concentrations and corresponded to the degree 
 of dyspnea when subjects experienced an unpleasant intensity after viewing a pleasant image . this is the first study to investigate the increase in dyspnea caused by the difference 
 between expected and actual dyspnea experiences , especially in relation to the finding of 
 increased oxy - hb in the rmpfc . one of our principal objectives was to evaluate the relative changes in expectations and 
 cortical activation . importantly , we observed positive correlations between the borg scale 
 measurements and rmpfc indices . increased rmpfc activity was associated with emotions such 
 as discomfort or aggression . evaluated the role of the prefrontal cortex in 
 healthy volunteers during emotional stress by showing subjects affective pictures , and they 
 determined that cerebral activation increased with stressful thinking , particularly in the 
 prefrontal cortex , anterior cingulate cortex , and insula27 . however , rmpfc activity did not change in any of the other 
 conditions used in the protocol . previous studies have also used affective images to study the relationships between 
 attention , emotion , and brain activity28 . grimm et al . reported that increased dlpfc and mpfc activity were evoked by inducing 
 emotions using the international affective picture system29 . suggested that the late positive component of 
 central parietal lobe activity increases when discomforting pictures are perceived at an 
 early stage30 . in agreement with this , our results show that oxy - hb of dlpfc activation increased when subjects were provided with 
 discomforting information at an early stage . we can conclude that the main factors associated with dyspnea are differences in bilateral 
 activity and the timing of the functional mechanism in the pfc of normal subjects . little is 
 known about the underlying mechanisms of dyspnea ; however , our results indicate that rmpfc 
 increases oxy - hb , which in turn induces emotional stress resulting in discomfort . dyspnea is 
 not only induced by external stimuli , but rather has multiple activators ( unpleasant and 
 emotional impacts)31 . leupoldt et al . 
 showed that increasing the unpleasantness led to an enhancement in the sensory aspects of 
 dyspnea32 . it is known that stress and 
 discomfort levels can affect changes in brain activity in the mpfc28 , 33 . for the 
 volunteers in our study , respiratory sensations presumably became highly relevant and 
 demanded attention , resulting in increased neural processing , thus risking overperception 
 and the amount of air required to recover . moreover , our research suggests that dyspnea is 
 correlated with rmpfc activity when subjects need to recover an amount of air , whereas it is 
 not in other processes . based on these results , we speculate that human breathing readjusts 
 itself immediately after experiencing new respiratory sensations . in summary , the present study found increased neural processing in terms of increased 
 oxy - hb in the rmpfc when this effect 
 might represent a negative neural feedback mechanism that becomes active when the subject 
 becomes aware of the difference between the expected and actual air supply . our research 
 suggests that dyspnea is affected not only by external stimuli , but also by internal 
 perceptions and expectations generated from prior experiences . therefore , in clinical 
 settings , we suggest that therapists should not expose subjects to respiratory intensities 
 that are stronger than expected . principally , 
 fnirs was unable to investigate the activity of the whole brain because it can only detect 
 cortical hemodynamics . however , we were able to monitor brain activity without physical 
 restrictions or discomfort . in conclusion , our study using fnirs demonstrated a correlation 
 between increased oxy - hb in the rmpfc and dyspnea in healthy subjects . further research will 
 be necessary to determine the relationship between different ways of thinking and the level 
 of dyspnea in healthy subjects .
[ purpose ] oxygenated hemoglobin ( oxy - hb ) concentrations in the prefrontal cortex are 
 closely associated with dyspnea . 
 dyspnea is influenced not only by physical activity , but 
 also by visual stimuli , and several studies suggest that oxy - hb concentrations change in 
 response to certain external stimuli . 
 however , the effects of internal psychological 
 states on dyspnea have not been reported . 
 this study explored the influence of 
 anticipation triggered by previous episodes of dyspnea on brain activity . 
 [ subjects ] the 
 subjects were 15 healthy volunteers with a mean age of 25.0  3.0  years . [ methods ] the 
 subjects were shown a variety of photographs and instructed to expect breathing resistance 
 matched to the affective nature of the particular photograph . 
 after viewing the images , 
 varying intensities of breathing resistance that were identical to , easier than , or harder 
 than those shown in the images were randomly administered to the subjects ; in fact , the 
 image and resistance were identical 33% of the time and discordant 66% of the time . 
 [ results ] the concentrations of oxy - hb in the right medial prefrontal cortex ( rmpfc ) 
 increased significantly with an inspiratory pressure that was 30% of the maximum intensity 
 in the subjects shown a pleasant image compared to the concentrations in subjects shown an 
 unpleasant image . 
 moreover , rmpfc activity was significantly correlated with the magnitude 
 of the dyspnea experienced . 
 [ conclusion ] these results suggest that a correlation exists 
 between increased oxy - hb in the rmpfc and the effects of expectations on dyspnea .