Emotional-stimulus processing in trait anxiety is modulated by stimulus valence during neuroimaging of a working-memory task

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Abstract
Recent neuroimaging studies have examined the effects of anxiety on cognitive processing in the presence of emotional distractors. However, when the target stimuli themselves are emotional, it is unclear whether emotion acts as a distracting or enhancing influence. We predicted that anxiety levels would modulate the effect of emotion on neural activity in a valence-specific manner. In the current experiment, we used functional magnetic resonance imaging (fMRI) to examine activity in brain regions associated with cognitive and affective control. Twenty-nine healthy adults, rated for trait anxiety, performed blocks of a 2-back working-memory task (using faces) in which facial expressions were either entirely neutral, mixed neutral and fearful, or mixed neutral and happy. Behavioural results showed no effects of anxiety on either accuracy or response time for any stimulus type. In event-related analyses, dorsal prefrontal regions tended to show reduced activation for emotional faces relative to neutral, suggesting possible neural facilitation, while the amygdala and ventrolateral regions linked to affective-interference showed increased activation to emotional faces. Moreover, in the left inferior frontal gyrus (Brodmann area 45), anxiety discriminated between the response to happy trials and fear trials. The higher the anxiety score, the greater the increase in activation for fear faces versus neutral. By contrast, the lower the anxiety score, the greater the increase in activation to happy faces. These results suggest that emotional content in target stimuli can both enhance and interfere with neural processing, and these effects may depend on emotional valence and participants' anxiety levels.