| Rumination, or recursive thinking about one's symptoms and the consequences of those symptoms, has important implications regarding the development and maintenance of depressed moods. Rumination may also enhance cognitive biases by heightening affective responses to negative material, increasing access to negative memories, and diminishing successful regulation of affect. It is, therefore, important to understand the basis of rumination, including the neural substrates involved. The present study examined rumination in depressed and healthy control individuals using fMRI. Depressed (MDD) and control (CTL) participants underwent functional imaging while focusing on blocks of statements including Rumination, Abstract Distraction, Concrete Distraction, and a Fixation (Baseline) condition. It was predicted that, during ruminative self-focus depressed individuals would exhibit increased neural responding in areas subserving affective responding (including limbic regions), autobiographical memory retrieval (e.g., hippocampus and parahippocampus), and attenuated activation in areas associated with regulation of affect (e.g., dorsal regions). Ratings of positive affect (PA) and negative affect (NA) were also assessed after each block of statements.; MDD participants indicated more NA and less PA than CTL participants across all conditions. Consistent with behavioral reports suggesting that rumination should differentially affect negative mood in depressed individuals, the MDD group gave the highest NA ratings after Rumination blocks. With respect to the neural correlates of rumination, as predicted, during ruminative self-focus conditions contrasted with distraction conditions, MDD participants exhibited increased activation in emotion processing centers (i.e., amygdala, rostral anterior cingulate, subgenual cingulate, and orbitofrontal cortex) and areas associated with autobiographical memory (i.e., parahippocampus). Further, it was demonstrated that percent signal change in the amygdala was significantly correlated with self-reported rumination. Interestingly, though not predicted, the MDD participants also exhibited increased activation in dorsolateral prefrontal cortex across all of the contrast; this suggests that, during ruminative self-focus, depressed individuals may attempt to engage in more effortful regulation. These findings represent the first account of the network of neural regions involved during ruminative self-focus in depressed individuals and add to our growing understanding of the ways in which the brain is dysregulated during depression. |
