Face processing occurs outside the fusiform 'face area' in autism: evidence from functional MRI

Processing the human face is at the focal point of most social interactions , yet this simple perceptual task is difficult for individuals with autism, a population that spends limited amounts of time engaged in face-to-face e ye contact or social interactions in general. Thus, the study of face proce ssing in autism is not only important because it may be integral to underst anding the social deficits of this disorder, but also, because it provides a unique opportunity to study experiential factors related to the functiona l specialization of normal face processing. In short, autism may be one of the only disorders where affected individuals spend reduced amounts of time engaged in face processing from birth. Using functional MRI, haemodynamic responses during a face perception task were compared between adults with a utism and normal control subjects. Four regions of interest (ROIs), the fus iform gyrus (FG), inferior temporal gyrus, middle temporal gyrus and amygda la were manually traced on non-spatially normalized images and the percenta ge ROI active was calculated for each subject. Analyses in Talairach space were also performed. Overall results revealed either abnormally weak or no activation in FG in autistic patients, as well as significantly reduced act ivation in the inferior occipital gyrus, superior temporal sulcus and amygd ala. Anatomical abnormalities, in contrast, were present only in the amygda la in autistic patients, whose mean volume was significantly reduced as com pared with normals. Reaction time and accuracy measures were not different between groups. Thus, while autistic subjects could perform the face percep tion task, none of the regions supporting face processing in normals were f ound to be significantly active in the autistic subjects. Instead, in every autistic patient, faces maximally activated aberrant and individual-specif ic neural sites (e.g. frontal cortex, primary visual cortex, etc.), which w as in contrast to the 100% consistency of maximal activation within the tra ditional fusiform face area (FFA) for every normal subject. It appears that , as compared with normal individuals, autistic individuals 'see' faces uti lizing different neural systems, with each patient doing so via a unique ne ural circuitry. Such a pattern of individual-specific, scattered activation seen in autistic patients in contrast to the highly consistent FG activati on seen in normals, suggests that experiential factors do indeed play a rol e in the normal development of the FFA.