Implicit and explicit processing of facial emotion involves distinct neural pathways

Abstract

Some authors have proposed that implicit and explicit emotional processing involve distinct neural networks. The existing literature however is inconclusive and existing studies are limited both by the use of static displays of facial emotion, which have limited ecological validity, and MRI sequences that are not optimized for visualizing the amydala. We hypothesize differenzial activation of cortical and subcortical structures with implicit and explicit emotional processing respectively. We recruited 20 right handed healthy subjects (10 female, 10 male, mean age 29yrs.). They were scanned using a protocol that we had optimized for viewing the amygdala in a 1.5T Siemens Sonata Scanner (field of view 256mm, voxel size 4×4 x 4, TR 2500ms, TE 40ms). Stimuli included 40 different film clips from 10 professional actors who displayed neutral, positive (happy) and negative (fearful and sad) facial expressions. Subjects were engaged in two different tasks: during the implicit task, they had to identify the gender of the poser. For the explicit task they had to identify the emotion displayed. As hypothesized, cortical and subcortical structures were differenzially activated during implicit and explicit processing of dynamic displays of facial emotion. While explicit processing activated the amygdala more strongly, implicit processing lead to increased activation in the frontal cortex, anterior and posterior cingulum. The paradigm presented here may be used in further studies