The Impaired Inhibitory Control Of Insomnia Disorder

Insomnia disorder(ID)has been one of the most prevalent and common psychophysiological disorders.ID can be defined as a chronic difficulty which involves problems of initiating and/or maintaining sleep,poor sleep quality,or waking early in the morning not feeling restored,along with daytime cognitive dysfunctions despite of adequate sleep opportunity and environment.As one of the core executive functions,inhibitory control involves being able to control one's attention,behavior,and thoughts to override a strong internal predisposition or external lure,and instead do what's more appropriate or needed.Impaired inhibitory control can be found in many psychiatric disorders,but many researches pointed that insomnia disorder not presented impaired inhibitory control,which was in contradiction with the abnormal brain morphometry in the frontal cortex.The prefrontal cortex is the key brain area for inhibitory control,thus the abnormal brain morphometry of frontal cortex may lead to impaired inhibitory control in patients of insomnia.Therefore,we make the hypothesis that ID may present impaired inhibitory control,and two experiments will be conducted to test this hypothesis.Study 1,the auditory stop signal task and polysomnography was used to investigate whether ID presented impaired inhibitory motor control.Results indicated that patients of insomnia didn't differ from their matched controls for reaction times on Go trials,but the stop signal reaction time(SSRT)was significant slower in insomniacs compared with healthy good sleepers(HGS).Thus we can conclude that ID presented an impaired inhibitory motor control,but not the ability of response to stimulus.In addition,the SSRT of all participants showed positive correlation with Pittsburgh sleep quality index(PSQI),and negative correlation with slow wave sleep(SWS).The impaired inhibitory control of insomniacs may associate with poor sleep quality and the lower slow wave sleep.From study 1,we found that ID presented impaired inhibitory control,but its neuromechanism is also not clear.Theta and alpha rhythms were deemed to reflect cognitive control and inhibitory control,and medial prefrontal cortex generated frontal midline theta rhythm.The impaired inhibitory control and abnormal brain morphometry of frontal cortex in insomniacs all may indicate their abnormal theta and alpha thythms.Base on the assumption,we conducted the study 2.All participants were divided into three groups: patients with insomnia duration above 3 years(A3),patients with insomnia duration below 3 years(B3),Healthy good sleepers(HGS).Eye-closed rest-state EEG data were recorded about 5 minutes,and the toolbox of REsting-state COrtex rhythms(RECOR)was used to analyze the EEG data.Results indicated that,compare to HGS,only A3 group showed significant lower power in theta and alpha2 band,B3 and A3,B3 and HGS not presented significant difference.In other words,we can conclude that insomnia duration may be the key factor that influencing the power of theta and alpha2.Dorsal attention network(DAN),frontoparietal network(FPN),deep brain structure network(DSN)were cortical sources of the decreased theta power.DAN,FPN,DSN,and limbic network were cortical sources of the decreased alpha2 power.The power of FPN and DSN in theta band presented negative correlation with insomnia duration,which meant that the longer insomnia duration,the more impairment in cortical network of FPN and DSN.In sum,evidence from behavioral and rest-state EEG proved that ID got damaged inhibitory control.Based on the strict screening criteria in the subject and experiment paradigm selection,our study solved the divergence about whether insomniacs presented impaired inhibitory control in stop signal task.We found that insomnia duration was the key factor that influencing the power of theta and alpha2.And patients with insomnia duration above 3 years fell into the highest-risk group with abnormal EEG rhythms.Future studies and clinical treatment should pay more attention to insomnia duration above 3 years,and insomnia disorder is the psychiatric disease that needs timely treatment to avoid more aggregated influence on inhibitory control and EEG rhythms.