Neural changes associated with the generation of specific past and future events in depression

It is well established that individuals affected by depression experience difficulty in remembering the past and imagining the future. This impairment is evident in increased rumination on non-specific, generic events and in the generation of fewer specific events during tasks tapping past and future thinking. The present fMRI study investigated whether neural changes during the construction of autobiographical events was evident in depression, even when key aspects of performance (event specificity, vividness) were matched. We employed a multivariate technique (Spatiotemporal Partial Least Squares) to examine whether task-related whole brain patterns of activation and functional connectivity of the hippocampus differed between depressed participants and non-depressed controls. Results indicate that although the depression group retained the ability to recruit the default network during the autobiographical tasks, there was reduced activity in regions associated with episodic richness and imagery (e.g., hippocampus, precuneus, cuneus). Moreover, patterns of hippocampal connectivity in the depression group were comparable to those of the control group, but the strength of this connectivity was reduced in depression. These depression-related reductions were accompanied by increased recruitment of lateral and medial frontal regions in the depression group, as well as distinct patterns of right hippocampal connectivity with regions in the default and dorsal attention networks. The recruitment of these additional neural resources may reflect compensatory increases in post-retrieval processing, greater effort and/or greater self-related referential processing in depression that support the generation of specific autobiographical events.