State or trait? The aberrant effective connections of limbic circuits in recognition to happy face among depressed patients before and after antidepressant treatment

Abstract

Objective To investigate the aberrant effective connections of limbic circuits in patients with major depressive disorder when they recognized dynamic positive face expressions before and after antidepressant treatment, and to further explore whether the abnormal happy facial emotion processing was a state abnormality or a trait defect? Methods Twelve depressed patients and 12 well-matched healthy control volunteers participated in the study. All the subjects were scanned by magnetoencephalograph (MEG) when recognizing the emotion face images. Subjects in depression group were again performed the face recognition and MEG scanning after 8-10 weeks of standard antidepressant treatment. The MEG signals in response to happy face among orbitalfrontal cortex (OFC), the anterior cingulated cortex (ACC), the amygdala (AMYG), the hippocampus (Hipp), and the insula (Insu) were recorded at 0-600 ms. Principal component analysis (PCA) was used to reduce the dimensions, and the effective connectivity of the above interested brain areas was computed and tested by Granger causality model (GCM). The differences of effective connectivity in the interested brain areas between depressed patients and healthy control were analyzed by one-way ANOVA. Results (1)Among the above three groups, significant differences of effective connections were found in the connections of OFC to AMYG (F=3.927, P=0.030), Hipp to AMYG (F=4.132, P=0.025), Insu to AMYG (F=3.361, P=0.047), and AMYG to Hipp (F=7.470, P=0.002, FDR correction). (2) Compared with the healthy control group, the depressed patients before antidepressants treatment displayed higher activity in effective connections from OFC to AMYG (P=0.040), lower activity in effective connections from the ACC to the Hipp (P=0.042), and lower activity in effective connections both from AMYG to Hipp (P=0.001) and hipp to AMYG (P=0.026). (3) After antidepressants treatment, the activity of effective connections from the OFC to the AMYG significantly reduced (P=0.013), and the activity of connections both from AMYG to Hipp and from Hipp to AMYG significantly increased (P=0.006, 0.026), while the activity of effective connections both from AMYG to Insu and from Insu to AMYG significantly reduced (P=0.036, P=0.015). (4) Depressed patients after treatment showed no significant difference compared with the healthy control group. Conclusions The aberrant effective connection of the limbic system during positive emotion processing tasks may play an important role in explaining the abnormal positive emotion processing in depressed patients, which is a state abnormality instead of a trait defect, supported by the full recovery after antidepressant treatment. Key words: Major depressive disorder; Emotion; Magnetoencephalograph; Antidepressant; Granger causal model