Abstract
The natural time course of mood includes both acute responses to stimuli and spontaneous fluctuations. To date, neuroimaging studies have focused on either acute affective responses or spontaneous neural fluctuations at rest but no prior study has concurrently probed both components, or how mood disorders might modulate these processes. Here, using fMRI, we capture the acute affective and neural responses to naturalistic positive mood induction, as well as their spontaneous fluctuations during resting states. In both healthy controls and individuals with a history of depression, our manipulation acutely elevates positive mood and ventral striatum activation. Only controls, however, sustain positive mood over time, and this effect is accompanied by the emergence of a reciprocal relationship between the ventral striatum and medial prefrontal cortex during ensuing rest. Findings suggest that corticostriatal pathways contribute to the natural time course of positive mood fluctuations, while disturbances of those neural interactions may characterize mood disorder.
Highlights
The natural time course of mood includes both acute responses to stimuli and spontaneous fluctuations
The analysis of variance (ANOVA) revealed a main effect of Time (F(4,216) 1⁄4 18.57, Po0.001), due to a significant increase in positive mood immediately following the mood induction manipulation, as well as a main effect of Group (F(1,54) 1⁄4 5.30, P 1⁄4 0.025), owing to an overall more positive mood in the control compared with recurrent MDD (rMDD) group
We aimed to investigate whether acute neural responses to positive stimuli interact with the default mode network (DMN) at subsequent rest, and evaluate the potential contribution of such neural interactions to the natural time course of positive mood fluctuations
Summary
The natural time course of mood includes both acute responses to stimuli and spontaneous fluctuations. The overarching goal of the current study was to address these important gaps in the literature by probing the acute and sustained affective and neural responses to naturalistic positive mood induction, as well as their spontaneous fluctuations during subsequent resting states To achieve this goal, we developed a novel task involving humour processing and delivery of selfreferential positive feedback (Fig. 1). Owing to the fact that positive mood disturbances are core characteristics of MDD that often persist following remission, the inclusion of a clinical sample allowed us to test fundamental questions about how mood disorders might modulate the neural substrates of mood regulation Both currently depressed and remitted individuals with a history of depression exhibit attenuated acute response to positive information[10,11], as well as reduced preservation of positive affect in the absence of external stimuli[12,13]. We expected that mood dysregulation in rMDD would be linked to abnormal neural interactions between the VS and DMN during rest
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