Abstract
The ventrolateral prefrontal cortex (VLPFC) and amygdala have critical roles in the generation and regulation of unpleasant emotions, and in this study the dynamic neural basis of unpleasant emotion processing was elucidated by using paired-samples permutation t-tests to identify the timing of emotional discrimination in various brain regions. We recorded the temporal dynamics of blood-oxygen-level-dependent (BOLD) signals in those brain regions during the viewing of unpleasant pictures by using functional magnetic resonance imaging (fMRI) with high temporal resolution, and we compared the time course of the signal within the volume of interest (VOI) across emotional conditions. Results show that emotional discrimination in the right amygdala precedes that in the left amygdala and that emotional discrimination in both those regions precedes that in the right anterior VLPFC. They support the hypotheses that the right amygdala is part of a rapid emotional stimulus detection system and the left amygdala is specialized for sustained stimulus evaluation and that the right anterior VLPFC is implicated in the integration of viscerosensory information with affective signals between the bilateral anterior VLPFCs and the bilateral amygdalae.
Highlights
The human brain contains neural circuits responsible for the emotional responses elicited by stimuli, and the amygdala and prefrontal cortex (PFC) are key components of these circuits (Davidson and Irwin, 1999)
The time courses of positive peaks activated by unpleasant picture stimuli were steeper, relative to those of positive peaks activated by neutral picture stimuli, in the bilateral amygdalae and the left anterior ventrolateral prefrontal cortex (VLPFC), whereas in the primary visual cortex and the right anterior VLPFC those time courses were almost the same
Investigating the timing of emotional discrimination in the bilateral VLPFCs and the bilateral amygdalae during the viewing of unpleasant pictures, we found that the emotional discrimination in the right amygdala preceded that in the left amygdala and that the emotional discrimination in both these regions preceded that in the right anterior VLPFC
Summary
The human brain contains neural circuits responsible for the emotional responses elicited by stimuli, and the amygdala and prefrontal cortex (PFC) are key components of these circuits (Davidson and Irwin, 1999). Recent functional magnetic resonance imaging (fMRI) studies have shown functional connectivity between the VLPFC and the amygdala (Banks et al, 2007; Guyer et al, 2008; Tang et al, 2013; Townsend et al, 2013). When subjects reappraise unpleasant scenes in order to decrease the strength of the unpleasant feelings elicited, VLPFC activity is inversely correlated with amygdala activity (Ochsner et al, 2002; Wager et al, 2008). FMRI research on functional connectivity has clarified temporal correlations between the activity an unpleasant picture stimulus elicits in the VLPFC and the activity it elicits in the amygdala, the dynamic neural basis of unpleasant emotion processing in these regions remains unclear
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