Hemodynamic response in patients with Major Depressive Disorder and healthy subjects during autobiographical memory retrieval

Autobiographical memories (AMs), episodic memories of personally experienced events, are known to activate a specific left-lateralized network of brain regions, including the hippocampus, precuneus, anterior cingulate, and dorsolateral and ventrolateral prefrontal cortex, in healthy control (HC) participants. Patients with Major Depressive Disorder (MDD), compared to HCs, consistently recall fewer specific AMs, defined as memories occurring in a period of no longer than one day, and instead recall more categorical AMs, defined as summaries of recurring events. The current study examined the neurophysiological correlates of AM recall in patients with MDD, using functional Magnetic Resonance Imaging (fMRI), and the differences in the hemodynamic response between healthy controls (HC) and participants with MDD. Participants with MDD (N = 12) and HCs (N = 14) underwent fMRI scanning while recalling AMs in response to positive, negative, and neutral cue words. The hemodynamic response to AM recall was compared to a subtraction control task using the general linear model. Behavioral results showed fewer specific (p = .013) and more categorical (p < .001) AMs in participants with MDD compared to HCs. Additionally, participants with MDD recalled fewer positive AMs (p = .03), highly arousing AMs (p = .04), and AMs from the past 6 months (p = .02) as compared to the HCs. Overall, AM recall resulted primarily in activation in left prefrontal, temporal, and cingulate regions, as compared to the subtraction task. This pattern was seen in both the HCs and the participants with MDD. Differences were seen in the activation of the anterior cingulate, ventrolateral PFC, insula, and fusiform gyrus during AM recall in healthy controls as compared to participants with MDD. Additionally, the hippocampus showed greater activation in the HCs as compared to participants with MDD during recall of AMs from 6 months prior to scanning compared to subtraction. This result may explain why participants with MDD recalled fewer recent memories and supports the traditional theory of hippocampal involvement in recent memory recall. Understanding abnormalities in behavioral and neuropsychological responses to AM recall in participants with MDD may increase our understanding of MDD and lead to new behavioral interventions.