Distributed Neural Systems for Face Perception

Face perception plays a central role in social communication and is, arguably, one of the most sophisticated visual perceptual skills in humans. Consequently, face perception has been the subject of intensive investigation and theorizing in both visual and social neuroscience. The organization of neural systems for face perception has stimulated intense debate. Much of this debate has focused on models that posit the existence of a module that is specialized for face perception (Kanwisher et al., 1997 ; Kanwisher and Yovel, 2006 ) versus models that propose that face perception is mediated by distributed processing (Haxby et al., 2000 , 2001 ; Ishai et al., 2005 ; Ishai 2008 ). These two perspectives on the neural systems that underlie face perception are not necessarily incompatible (see Kanwisher and Barton, Chapter 7, this volume). In our work, we have proposed that face perception is mediated by distributed systems, both in terms of the involvement of multiple brain areas and in terms of locally distributed population codes within these areas (Haxby et al., 2000 , 2001 ). Specifically, we proposed a model for the distributed neural system for face perception that has a Core System of visual extrastriate areas for visual analysis of faces and an Extended System that consists of additional neural systems that work in concert with the Core System to extract various types of information from faces (Haxby et al., 2000 ). We also have shown that in visual extrastriate cortices, information that distinguishes faces from other categories of animate and inanimate objects is not restricted to regions that respond maximally to faces, i.e. the fusiform and occipital face areas (Haxby et al., 2001 ; Hanson et al., 2004 ). In this chapter we present an updated model of distributed human neural systems for face perception. We will begin with a discussion of the Core System for visual analysis of faces with an emphasis on the distinction between perception of invariant features for identity recognition and changeable features for recognition of facial gestures such as expression and eye gaze. The bulk of the chapter will be a selective discussion of neural systems in the Extended System for familiar face recognition and for extracting the meaning of facial gestures, in particular facial expression and eye gaze. We will discuss the roles of systems for the representation of emotion, for person knowledge, and for action understanding in face recognition and perception of expression and gaze. The neural systems that are recruited for extracting socially-relevant information from faces are an unbounded set whose membership accrues with further investigations of face perception. Rather than attempt an exhaustive review, our intention is to present systems that we believe are of particular relevance for social communication and that are illustrative of how distributed systems are engaged by face perception. Many of the chapters in this volume provide a more detailed account for areas that we touch on in this chapter. Our review also is biased towards work that we have been directly involved in, with selective references to closely related work by other investigators. We will finish with a discussion of modularity and distributed processing in neural representation. C6.S1