Chapter 10 - Spatial distribution of face and object representations in the human brain

Abstract

This chapter discusses a hypothesis for the functional organization of object-responsive cortex, which posits that the representation of a viewed face or object is not restricted to neural activity in cortex, responding maximally to that face or object. Therefore, representations of faces and different object categories in face- and object-responsive cortices are distributed and overlapping. The chapter details the ventral object-vision pathway that shows that the perception of faces, color, and shape evoke neural activity in regions of the inferior occipital, fusiform, and lingual gyri; locally distributed representations of faces and objects in ventral temporal cortex; extended distribution of face and object representations, and spatially distributed face and object representations. The discussed hypothesis is not necessarily inconsistent with other principles of organization, particularly the roles of expertise and retinotopy, but allows more direct investigation of the way information about the visual appearance of faces and objects is encoded by neural activity in these regions. This hypothesis results from the demonstration that information about the face or object being viewed is carried not only by the activity in regions, responding maximally to that face or object, but is also by activity in regions that respond more strongly to the categories other than that of the currently viewed stimulus. This introduces a new method for fMRI data analysis— that is, multivoxel pattern analysis (MVPA). MVPA shows that information about the face or object being viewed is carried by distributed patterns of response in which both strong and weak levels of activity play a role. The patterns that are detected by MVPA are related more directly to the distributed population responses than encode visual information and, thus, helps to find out the way neural codes for faces and objects are organized, and where they may exist.