Segregated processing of facial identity and emotion in the human brain: A pet study

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Abstract
The brain is organized into segregated areas of relative functional autonomy and specialization. This basic principle of cerebral organization is well documented for cognitive functions that differ drastically from one another, but less so for functions that belong to the same domain, such as face processing. Yet several sources of evidence point to a functional and structural dissociation of various aspects of face processing, as suggested by (1) an analysis of the perceptual and cognitive demands made by the processing of diverse properties conveyed by facial configurations, (2) selective impairment of aspects of face processing in brain-damaged patients, and (3) different localizations of face cells responsive to properties conveyed by faces such as identity and emotion in the monkey's brain. This study used positron emission tomography (PET) and magnetic resonance imaging (MRI) to delineate better the neurofunctional organization of face processing in the human brain, by measuring cerebral blood flow while subjects performed tasks involving the recognition of faces or the recognition of emotions expressed by faces. The results showed segregated processing of facial identity and facial emotion, with the former being performed predominantly in the ventro-mesial region of the right hemisphere including the limbic system, whereas the latter was carried out predominantly in the latter part of the right hemisphere and the dorsal region of the limbic system. This structural organization allows the parallel processing of different information contained in physiognomies and underlies the high efficiency with which humans process faces.