RESUMEN
Objective To explore the effects of abnormal effective connectivity within the default mode network (DMN)in relapsed patients with major depressive disorder.Methods Resting-state functional magnetic resonance imaging (rs-fMRI)data were collected from 21 patients of first-episode depression and 16 patients with relapsed depression,and 37 matched healthy controls.The effective connectivity within the DMN was investigated with spectral dynamic causal modeling (spDCM)method.Results spDCM analysis showed that the effective connections from left parietal cortex(LPC)to right parietal cortex(RPC)and medial frontal cortex(mPFC)were significantly decreased,while the connection from posterior cingulate cortex(PCC)to mPFC was increased in patients of first episode depression compared to healthy controls.Furthermore,the connectivity between mPFC and LPC were enhanced in patients with recurrent depression compared withhealthy control subjects,as well as PCC.Meanwhile,the connectivity between mPFC and PCC was enhanced in patients with relapse depression compared with patients of first episode depression.Conclusion Both first-episode and relapsed patients demonstrated abnormal effective connectivity of LPC,implicating that abnormal LPC connectivity may be associated with the neural substrates of depression.In contrast,the patients with relapsed depression showed aberrant connectivity with the mPFC,suggesting that abnormal effective connectivity of the mPFC may play an important role in the relapse of depression.
RESUMEN
A number of studies have indicated that disorders of consciousness result from multifocal injuries as well as from the impaired functional and anatomical connectivity between various anterior forebrain regions. However, the specific causal mechanism linking these regions remains unclear. In this study, we used spectral dynamic causal modeling to assess how the effective connections (ECs) between various regions differ between individuals. Next, we used connectome-based predictive modeling to evaluate the performance of the ECs in predicting the clinical scores of DOC patients. We found increased ECs from the striatum to the globus pallidus as well as from the globus pallidus to the posterior cingulate cortex, and decreased ECs from the globus pallidus to the thalamus and from the medial prefrontal cortex to the striatum in DOC patients as compared to healthy controls. Prediction of the patients' outcome was effective using the negative ECs as features. In summary, the present study highlights a key role of the thalamo-basal ganglia-cortical loop in DOCs and supports the anterior forebrain mesocircuit hypothesis. Furthermore, EC could be potentially used to assess the consciousness level.