Effective Connectivity within a Core Cortical Network of Face Perception: Evidence for Inferior Occipital Gyrus sensitivity for Faces with Implicit Emotion

Emotional face perception is a highly developed visual skill in humans that occurs along a distributed neural system including: visual, limbic, and prefrontal areas of the human brain. It has been proposed that the core regions of face perception include the inferior occipital gyrus (IOG), fusiform gyrus (FG), and superior temporal sulcus (STS). We examined the modulation of effective connectivity within these core regions during a social judgment task of affective stimuli. Emotional low spatial frequency hybrids were created, where the emotion was implicit and an apparent neutral expression was displayed, and was used in this study along with explicit expressions. Two separate event-related functional magnetic resonance imagining (fMRI) experiments performed on the same participants were analyzed and assessed with dynamic causal modelling (DCM) to characterize effective connectivity within core regions of face perception. We found significant modulation on both IOG to FG and STS connections for all facial conditions with the favored model being the IOG to FG connection. Additionally, we found that the emotional low spatial frequency hybrids, which were morphed with high spatial frequency neutral expressions, and neutral faces led to prominent modulation in effective connectivity from IOG to STS connection. This result suggests that the IOG is sensitive to implicit emotional faces and sorts them differently than explicit emotional faces.