The role of emotion on visual perception

While the amygdala is known to play an important role in the modulation of visual perception by emotion, the pathways mediating such modulation are only partly understood. Using attentional blink and fear conditioning paradigms, I investigated neural pathways through which acquired affective significance of stimuli enhances perceptual awareness in competitive visual processing. I hypothesized that affective learning would strengthen sensory signals in visual cortex through indirect (mediated by attentional regions) and direct feedback connections of the amygdala, which would lead to behavioral privilege of affective stimuli in visual perception. Participants were asked to identify the first face target (T1; three identities) and categorize the second scene target (T2: building, house, or no-scene) presented along with other distractors in a rapid serial visual presentation (RSVP). The affective significance of T2 was manipulated via the prior fear conditioning, in which either building or house images were paired with unpleasant electric shock. Behaviorally, participants showed better detection for the scene category which was previously paired with shock (CS+) compared to the other category (CS-). The ROI analyses revealed significantly stronger fMRI responses for correctly identified CS+ T2 trials relative to correctly identified CS- T2 trials in the right amygdala, right parahippocampal gyrus, and several fronto-parietal regions including the middle frontal gyrus. Contrarily, there was no difference when participants were unaware of T2 scenes which were physically presented. My main hypothesis for the neural pathways of affective perception was tested by mediation analyses. The differences of fMRI responses in the right amygdala showed a positive correlation with the behavioral difference across participants and this effect was fully mediated by the T2-related right parahippocampal gyrus. Importantly, the total effect of the right amygdala on the right parahippocampal gyrus was further partitioned into the significant indirect effect partially mediated by the right middle frontal gyrus and the significant direct effect. My results suggest that acquired affective significance of stimuli determines the fate of a visual event in competitive visual perception by enhanced sensory-related activities through indirect and direct projections from the amygdala to visual processing areas, which eventually serves behaviorally important goals.