The goal of this proposal is to understand the neural circuits of the macaque brain mediating face perception. Faces are among the most meaningful visual forms processed by the primate brain, conveying information about identity, expression, gender, age, and direction of attention. Functional magnetic resonance imaging (fMRI) reveals a specialization for face processing in the macaque temporal lobe: six discrete regions of cortex respond much more strongly to images of faces than to images of other objects. The degree of specialization of these regions for faces is breathtaking: when targeted for single-unit recording, all four regions tested extensively so far turned out to consist almost entirely of face-selective cells. These regions, termed "face patches", are located at similar positions in the two hemispheres and across individuals. Experiments combining fMRI with microstimulation demonstrate that the face patches are strongly and specifically interconnected, yet electrophysiological experiments show that different patches are functionally distinct. The face patch system offers a unique opportunity to dissect the neural mechanisms underlying form perception, because the system is specialized to process one class of complex forms, and because its computational components are spatially segregated. We believe the central experimental challenge to understanding the face patch system is to understand the functional specialization of each patch and how this specialization comes about. To address this challenge, we plan to interrogate the system from four directions: 1) Representations: What are the selectivity and invariance properties of cells in each face patch?, 2) Behavioral Role: What is the effect of inactivating specific face patches on various face-related behaviors?, 3) Connectivity: What is the wiring diagram of the face patches?, and 4) Transformations: What are the key functional differences between input and output cells within each face patch? Addressing these questions will elucidate the principles of information flow within the face patch system and shed light on the general organizing principles of inferotemporal cortex.
A sizable fraction of humans suffer from prosopagnosia, a selective inability to recognize faces;our basic research on the face system in macaques aims to gain new insights concerning the brain circuits that are altered in prosopagnosics. Faces are by far the most socially significant class of visual stimuli that we perceive, and our results may shed new light on disorders of social cognition such as autism and social anxiety disorder.
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