Abstract
BackgroundThe fundamental mechanism underlying emotional processing in major depressive disorder (MDD) remains unclear. To better understand the neural correlates of emotional processing in MDD, we investigated the role of multiple functional networks (FNs) during emotional stimuli processing.MethodsThirty-two medication-naïve subjects with MDD and 36 healthy controls (HCs) underwent an emotional faces fMRI task that included neutral, happy and fearful expressions. Spatial independent component analysis (sICA) and general linear model (GLM) were conducted to examine the main effect of task condition and group, and two-way interactions of group and task conditions.ResultsIn sICA analysis, MDD patients and HCs together showed significant differences in task-related modulations in five FNs across task conditions. One FN mainly involving the ventral medial prefrontal cortex showed lower activation during fearful relative to happy condition. Two FNs mainly involving the bilateral inferior frontal gyrus and temporal cortex, showed opposing modulation relative to the ventral medial prefrontal cortex FN, i.e., greater activation during fearful relative to happy condition. Two remaining FNs involving the fronto-parietal and occipital cortices, showed reduced activation during both fearful and happy conditions relative to the neutral condition. However, MDD and HCs did not show significant differences in expression-related modulations in any FNs in this sample.ConclusionsSICA revealed differing functional activation patterns than typical GLM-based analyses. The sICA findings demonstrated unique FNs involved in processing happy and fearful facial expressions. Potential differences between MDD and HCs in expression-related FN modulation should be investigated further.
Highlights
The fundamental mechanism underlying emotional processing in major depressive disorder (MDD) remains unclear
During the processing of fearful faces, there is increased neural activation in the amygdala [11, 12], fusiform gyrus [12, 13], inferior frontal gyrus, superior temporal sulcus (STS) [14], and orbitofrontal cortex [15], and deactivation in the ventral anterior cingulate cortex (ACC) [14] in healthy participants. Most of these areas have been implicated in MDD [16], there is greater activation in amygdala, fusiform gyrus, inferior parietal lobule, inferior frontal gyrus [10], and lower activation in dorsolateral prefrontal cortex (DLPFC) [17], temporal cortex and insula [5] and inferior frontal gyrus [18]
In Spatial independent component analysis (sICA), among the 32 independent components (ICs) classified as functional networks (FNs), five showed significant main effects of task condition
Summary
The fundamental mechanism underlying emotional processing in major depressive disorder (MDD) remains unclear. During the processing of fearful faces, there is increased neural activation in the amygdala [11, 12], fusiform gyrus [12, 13], inferior frontal gyrus, superior temporal sulcus (STS) [14], and orbitofrontal cortex [15], and deactivation in the ventral anterior cingulate cortex (ACC) [14] in healthy participants. MDD has been associated with increased activation in medial frontal gyrus, insula, middle temporal gyrus and middle occipital gyrus [10], and reduced activation in temporal cortex and insula [21] These studies were conducted using an hypothesis-driven approach that assesses for differences within several specific networks or between a few regions of interest; such approaches could be biased by a priori definition of regions or networks and do not allow for a broad, discovery-based investigation of neural networks that may contribute to emotional processing differences
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