Winston, Joel S; (2005) Emotive aspects of face perception and the human brain. Doctoral thesis , UCL (University College London).

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Abstract

The neural mechanisms by which faces are processed are the subject of great interest. A key characteristic of human faces is the ability to induce emotion in the viewer, through expressed emotion or other more abstract constructs such as trustworthiness or attractiveness. In this thesis, five functional magnetic resonance imaging experiments that probe the neural systems underpinning the perception of such emotive characteristics are described. I show that perception of emotional expression and identity are doubly dissociable with fusiform cortex encoding identity and superior temporal sulcus (STS) encoding expression. In subsequent experiments I explore the parameters under which distinct brain regions involved in emotional face perception engage, in particular addressing whether responses are automatic or dependent upon a particular task. The issue of whether distinct emotions are processed by different brain regions is considered and the basic stimulus property of spatial frequency is manipulated to address the idea of a subcortical visual pathway carrying emotional information. I describe two further experiments that address the more complex social constructs of attractiveness and trustworthiness, and demonstrate that broadly similar cortical circuitry is invoked when processing these attributes compared to basic facial emotions. Ultimately, a network of brain regions including amygdala, fusiform cortex, STS, and orbital and medial prefrontal cortex (OMPFC) is characterised as the substrate for emotional face perception. In general, I found that amygdala and fusiform responses to emotive faces are automatic, whereas STS and OMPFC responses show a greater degree of task-dependence. I interpret the amygdala response as an emotional labelling process, whereas fusiform enhancements to emotive faces probably reflect feedback from amygdala to modulate early face processing. STS responses indicate the encoding of specific facial expressions in this region and a wider role in intention detection. The response profile of the OMPFC is complex and I suggest multiple roles for this region in mediating an interaction between cognition and emotion.

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