The Neuroimaging Study Of Thalamus Structural And Functional Changes In Primary Insomnia Patients

Insomnia disorder is one of the most prevalent and distressing psychiatric diseases.Insomnia impairs quality of life,hinders occupational and social functioning,and increases vulnerability to medical illnesses.Insomnia has also led to an increase in health care utilization and consequent social burden and economic costs.For the past decade,the neurobiological mechanism of insomnia has been widely investigated using advanced neuroimaging methodologies.Thalamus plays a critical role in the regulation of sleep-awake cycle.Besides,insomnia is highly comorbid with anxiety disorder and depression.Based on these evidences,the exact neural mechanism of insomnia still remains unclear.Therefore,primary insomnia(PI)was studied by magnetic resonance imaging(MRI)in the present dissertation.Based on the extensive literature demonstrating the critical roles of the thalamus in sleep regulation,we hypothesized that insomnia would be associated with functional and structural changes of the thalamus.This information is needed to better understand the neural mechanisms of insomnia,and would be useful for informing future attempts to alleviate or treat insomnia symptoms.Twenty-seven PI patients and 39 matched healthy controls were included in the present study.Volume and resting-state functional connectivity(RSFC)of thalamus were compared between groups,and the relationships between neuroimaging differences and clinical features also were assessed.Compared with the control group,the PI group showed significantly reduced volume of thalamus.In addition,several brain regions showed reduced RSFC with thalamus in PI patients,such as orbitofrontal cortex(OFC),anterior cingulate cortex(ACC),caudate,hippocampus and putamen.Correlation analyses revealed that,several of these RSFC patterns were negatively correlated with Pittsburgh Sleep Quality Index(PSQI)score among PI patients.Negative correlation was also observed between the RSFC strength of right thalamus–right ACC and Self-Rating Depression Scale(SDS)score in PI patients.This work demonstrates the structural and functional abnormalities of the thalamus in PI patients that were associated with key clinical features of insomnia.These data further highlight the important role of the thalamus in sleep and PI.PI is strongly associated with emotional dysregulation,which may explain its high comorbidity with disorders such as anxiety and depression.However,the neurobiological pathology of the association between PI and emotional dysregulation is limited.Previous studies have indicated an impact of PI on brain regions involving the emotional regulatory system,but the specificity of this finding remains to be confirmed.Therefore,this study investigated the association between insomnia severity and functional connectivity density(FCD)in PI patients and examined whether the FCD were associated with their elevated anxiety and depression levels.Our findings indicated that PI patients exhibited higher levels of anxiety and depression,but the insomnia-associated ACC was only related to their anxiety level,suggesting that association between insomnia and anxiety has an incremental organic basis but that for depression could be a threshold issue.This finding improved our understanding of insomnia and its comorbid affective disorder and provided helpful information for future therapeutic development.In conclusion,this study has enhanced our understanding of the neural mechanism of primary insomnia and provided scientific evidence for future treatment and relief of insomnia symptoms.