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Abstract

Background Major depressive disorder (MDD) is a highly prevalent psychiatric condition in which patients often have difficulties regulating their emotions. Prior studies have shown that attention bias towards negative emotion is linked to activation in regions of the default mode network (DMN) in MDD individuals. Furthermore, MDD patients showed increased resting-state functional connectivity (FC) between the medial prefrontal cortex and other DMN structures. Methods Twenty-one MDD patients that currently experiencing depressive episodes and twenty-five healthy control participants performed the current emotional expectancy paradigm in a gradient-echo SENSE-SPIRAL fMRI. Whole brain and psycho-physiological interaction (PPI) analysis were applied to explore the task-related brain activity and FCs. Results Relative to healthy participants, we found MDD patients had greater activity in dorsal medial prefrontal cortex as a function of positive vs. neutral expectancy conditions. PPI results revealed a significant group difference of MDD patients having relatively decreased task-dependent decoupling from dorsal medial prefrontal cortex (DMPFC) towards posterior cingulate cortex (PCC) and parieto-occipital cortex during positive vs. neutral expectancy conditions, and patients exhibited a positive correlation between PPI (DMPFC and PCC) and anhedonia as measured via SHAPS during the same conditions. Limitations Modest sample size and lack of concurrent depressive episodes limit the generalizability of our findings. Conclusions In MDD patients, insufficient DMN decoupling might occur in response to positive expectancy conditions. Our findings are consistent with the hypothesis that high intrinsic DMN connectivity in MDD patients interfere with the down-regulation of intrinsic focus in order to incorporate information derived from external positive events.