| The autistic traits reflect mild impairment of social interaction and communication in traditional population subthreshold,which consistent with the core symptoms of Autism Spectrum Disorder(ASD).Which means individuals with autistic traits are widespread within traditional population,the only difference is severity compared to clinical ASD.Since 2013,DSM-5 has not classified autism,and the continuity of population clearly recognized from a categorical classification with or without autism to a quantitative classification with continuity,which also reflects the diversity and heterogeneity of autism to some extent.A growing number of researchers found that autistic traits have similar behavioral,personality and cognitive characteristics to ASD.In addition to genetic factors,individual’s internal environment factors,family environment factors,social environment factors formed risk factors and protective factors which are unique to autistic characteristics are unclear until now to some extent.Therefore,in this study,we explore the brain mechanism of autistic traits and its influencing factors which are helpful for the in-depth understanding of the cognitive neuropsychological mechanism of impaired brain function in individuals with autistic traits.In recent years,with the rapid development of MRI technology,like structural magnetic resonance imaging,resting state functional magnetic resonance imaging,task state functional magnetic resonance imaging,more and more researchers began to pay attention to the relationship between cognition,behavior and brain.At first,the research on ASD has become one of the difficulties issue due to the particularity characteristic of lower coordination of ASD population.Individuals with autistic traits have the similar behavioral performance and neuroimaging characteristics with the clinical autism patients,which providing more research programs for the study of the neurological mechanism of autism,and also offer valuable experiences and references to clinical research.Secondly,social cognitive function and executicve control ability has long been considered as core cognitive disorders shared by inividuals with autism spectrum disorders,yet its brain activity in situations involving more social information remains unclear.In addition,previous studies have paid more attention to the influence of environment on autistic traits.However,whether the environment exists as a risk factor or a protective factor has not been clearly discussed.Therefore,in this study,we use four studies including eightexperiments to investigate the neural basis of autistic traits and its influence factors and found the risk factors and protective factors of autistic traits,and also provide targeted intervention and treatment for ASD to some extent.In the first study,we examined the structural and functional basis of the brain in individuals with autistic traits.Experiment 1 examined the difference in individuals with autistic traits using structure magnetic resonance imaging by taking a large sample of subjects(n = 401,men: 111,age range:18-26).Based on voxel-based morphometry(VBM),the brain structure basis of autistic traits was analyzed.VBM does not need a prior assumption,that is,the analysis is not based on a specific structure,but a relatively fair and comprehensive comparison of anatomical differences in the whole brain between groups.The results mainly showed that the correlation between gray matter volume and gray matter density of the brain and the AQ(Autism Spectrum Quotient)was significant in these regions: the right middle frontal gyrus(MFG),which are involved in social processing and social reasoning;the left parahippocampal gyrus(PHG),which is involved in socioemotional behaviors and unconscious relational memory encoding;the right superior parietal lobule(SPL),which are involved in cognitive control and the ability to show attention to detail;the left orbitofrontal cortex(OFC),which involved in social reward;the left lingual gyrus(LG)and right middle occipital gyrus(MOG),which involved in processing vision;the right middle cingulate cortex(MCC),which involved in executive control ability.These findings revealed that people with autistic traits in the normal population have atypical development in gray matter volume and gray matter density,which may affect their social functioning and executice control ability.Previous studies have shown that gray matter volume and gray matter density in individuals gradually discard excess gray matter for efficient functioning as their cognitive function matures,which also called “pruning” function.However,in autistic trait groups,such "pruning" function is not reflected in the individual’s adult life,which means that the brain structure in individuals with autistic traits shows specific development compared with traditional development people.Experiment 2 used resting functional magnetic resonance(f MRI)data of a large sample of subjects(n = 401,men: 111,age range: 18-26)to explore the characteristics of brain functional connections in individuals with autistic traits.Based on the resting-state functional connectivity,with the whole brain was conducted with the superior frontal gyrus(SFG),the superior parietal lobe(SPL),and inferior parietal lobe as the seeds.The results mainly showed that when using the SFG as the ROI region,the results showed significant increases in connectivity with the left MCC and decreases in the SPL.By using the right SPL as the ROI region,the results showed a significant decrease in connectivity with the right s OFC.By using the right IPL as the ROI region,the results showed a significant increase in connectivity with the left amygdale.The specific brain development of individuals with autism traits is mainly concentrated in the brain areas related to social cognition and executive control functions.These brain areas may be the key brain areas influencing autism traits and can be regarded as the neurobiological markers of autism traits.In the second study,we explored the brain mechanism of social cognitive and executive control task f MRI.Experiment 3(n = 106,men: 80,age range: 18-25)used emotional recognition task to explore the negative emotional processing ability.To explore the functional characteristics of the brain of individuals with autistic traits in processing negative emotion task.Participants were asked to pay attention to the pictures displayed in screen and rate the negative emotional intensity of the picture from 1 to 5 points.The results showed that the right MTG(middle temporal gyrus)was activated in watch negative-watch neural conditions.The mediation analysis found that the right MTG suppressed the relationship between the AQ(total)score and negative emotion。g PPI(generalized psychophysiological interaction)analysis revealed the AQ(total)score was related to higher functional connectivity between the right MTG and left parahippocampal gyrus(PHG)and left precuneus cortex.PHG is responsible for aotubiographical memory,and unconsicious processing information,precounuous is responsible for episodic memory and related to themselves brain area.The increased functional connectivity between MTG and the two may reflect that individuals with autistc traits might overprocess negative emotion unconsiciously,and their attention shift ability of social information are weak.These results indicated that,individuals with autistic traits tend to ignore dangersous information in the picture and to deduce what happened in this picture,which means they lack the ability to avoid danger.To some extent,this processing tendency is unique to the adolescent with autistic traits,and is one of the important reasons for the abnormal neural development of the individuals with autistic traits.In experiment 4(n = 29,men: 11,age range: 19-20),the classical task paradigm stop-signal task was used to explore the neural basis of adolescents with autistic traits within inhibition control ability.It was found that the higher the AQ score,the longer the response time of SSRT(stop success reaction time).Then,group ICA(Group independent Component Analysis)was performed to analyze the functional connectivity.The ICA component was used as the seed to analyze the functional connectivity.It was found that the functional connectivity between the lauguage network and the cerebellar vermis was increased,while the functional connectivity between the lauguage network and the ITG brain area was significantly decreased;the SN-SMG was decreased;DAN-LG was decreased.The cerebellum and anterior central gyrus participate in the bottom-up attention processing process,and the frontal parietal network,marginal superior gyrus and inferior temporal gyrus participate in the top-down inhibition and control process,which are closely related to executive function.Similarly,these brain regions also appeared in the ROI-ROI analysis study,which also verified the specific role of these four brain regions in the executive function of autistic traits from another aspect.In the third study,we explore the risk factors of neural mechanism of the social cognitive function in adolescents with autistic traits.Experiment 5(n = 365,men: 101,age range: 18-26)explored the influence of neural mechanism of neuroticism on adolescents with autistic traits.Using seed-based mediation analysis,the mediation analysis results showed that the right MFG has a partial effect between neuroticism score and AQ total score,which reflected individuals with higher neuroticism score,the right MTG of gray matter density has changed,the MFG plays an important role in individual’s emotion,flexibility and executive function.And this change enhances individuals’ characteristic of autistic traits.Experiment 6(n = 359,men: 96人,age range: 18-26)explored the influence of PRCA(personal report of communication apprehension)on individuals with autistic traits,using the same analysis method as the experiment 5,the results showed that the SPL has partial effect between team score and AQ total score which indicated that the higher the PRCA score,the higher SPL of gray matter density,which might lead to abnormal development of the brain,and enhanced the characteristic of autistic traits.Above two experiments we X mentioned suggested that individuals with high neuroticism,high communication comprehension are risk factors for the adolescents with autistic traits,which alter the gray matter volume and density such as MFG and SPL to some extent,and increased the risk of individuals formed high autistic traits,it might affect by the individual’s brain structure,when brain structure changed,it will affect the formation a development of the individuals with autistic traits.In the fourth study,we explored the neural mechanism of protective factors of social cognitive function of adolescents with autistic traits.Experiment 7(n = 365,men: 101,age range: 18-26)explored the neural mechanism of extraversion using seed-based mediation analysis,the results showed that there is a significant positive correlation between extraversion score and SPL of GMV,and a significant negative correlation between SPL of GMV and AQ total score,these results indicated that the SPL has a partial effect between extraversion score and AQ total score,which means the higher the extraversion score,the larger SPL of GMV,the lower of AQ total score.Experiment 8(n = 365,men: 101,age range: 18-26)explored the neural mechanism of openness using seed-based mediation analysis,the partial effect also found between openness and AQ total score,mediated by MFG.The results of this study indicated that extraversion and openness could be regarded as one of the protective factors of autistic traits to a certain extent.Individuals with higher extraversion and openness had more mature and stable brain structures,that is,smaller MFG of GMD and larger SPL of GMV.The SPL is in an increasing trend in the process of individual development,and reaches its peak in adolescence and then becomes stable.The decrease of gray matter volume in the SPL indicated that the inhibition control ability of individuals with autistic traits is impaired.Exercise and cultivate individuals’ enthusiasm,sociability,assertiveness,optimism and other positive qualities,the brain will change with the behavioral intervention to a certain extent,so as to achieve the protective effect.About all mentioned above,the present study results showed that the brain mechanisms of autistic traits mainly focus on the MFG of GMD,SPL of GMV,and the functional connectivity of SFG – MCC,SFG – SPL,SPL-s OFC,and IPL – amygdale.These brain areas and functional connectivity are the brain areas of social cognitive ability and executive control ability.Individuals with high level of autistic traits shown increased MFG of GMD,and decreased SPL of GMV,the increased functional connectivity between SFG and MCC,decreased functional connectivity between SFG and SPL,increased functional connectivity between SPL and s OFC,and increased functional connectivity between IPL and amygdala.These changes of the brain structure and functional connectivity might be the key neural foundations in individuals with autistic traits.Specifically,first,the MFG might be involved in social cognitive processing and social information reasoning,while the SPL might be involved in cognitive control and attention to detail.Additionally,the functional connectivity base on brain activation might be related to executive function,attention switching,the social reward system,and emotion recognition.The changes in brain structure might lead to the increased functional connectivity among frontal gyrus and temporal gyrus of emotional processing.Third,autistic traits affect the normal development and change of individual brain structure,and then affect individual emotional recognition ability,which is one of the core abilities of social cognitive function and executive control ability.In this study,we explored the risk factors and protective factors of the autistic trait,we might be find out which factors can play a protective role and which factors need to be paid attention.To sum up,this research could help people understand the core of the autistic traits of the brain neural basis from the level of cognitive neuroscience.The results of this study can help people to understand the neural basis of the brain at the core of autistic traits,understand the abnormal performance of individuals with autistic traits in the process of emotion recognition and response inhibition,and further demonstrate that individuals’ personality traits and social communication ability have a significant impact on autistic traits.The results of this study can also provide constructive guidance and suggestions for the recovery of mental health and cognitive function of autistic individuals.At the same time,it has certain enlightening effect on the diagnosis and treatment,intervention and training of autism by the combination of personality,environment and other factors. |
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