Subgenual anterior cingulate cortex activity covariation with cardiac vagal control is altered in depression

Background: We tested the hypothesis that subgenual anterior cingulate cortex (sgACC) participates in concurrently regulating shifts in both affective state and cardiac vagal control. Methods: Eleven healthy adults and 8 depressed subjects performed the Emotional Counting Stroop task in alternating 15-second blocks of emotion words and neutral words while undergoing functional magnetic resonance imaging (fMRI) and electrocardiography (ECG). We measured the absolute value of change between adjacent 15-second blocks in both cardiac vagal control and the BOLD signal in specific regions of interest. Results: Strong positive correlations were observed in healthy control participants between changes in cardiac vagal control and changes in BOLD signal intensity in sgACC (BA25) (right: r=.67, p<.02; left r=.69, p<.02), as well as other key structures in the medial visceromotor network. Depressed subjects showed no significant correlations between cardiac vagal control and BOLD signal intensity within BA25 or any other brain region examined. During the transition from depression-specific emotion blocks to neutral blocks, the correlation between BOLD signal change in BA25 and cardiac vagal control change was significantly greater in controls than in depressed subjects (p<.04). Conclusions: Findings in healthy volunteers suggest that sgACC participates in affective state shifting. The latter function appears to be altered in depressed individuals, and may have implications for the unvarying mood and vagal dysfunction associated with depression. Limitations: Limitations include a small sample size, an inability to disentangle afferent versus efferent contributions to the results, and the lack of a whole-brain analysis.