Toward direct visualization of the internal shape representation space by fMRI

Abstract

Reports of columnar organization of the macaque inferotemporal cortex (Tanaka, 1992, 1993a) indicate that ensembles of cells responding to particular objects may be both sufficiently extensive and properly localized to allow their detection and discrimination by means of functional magnetic resonance imaging (fMRI). A recently developed theory of object representation by ensembles of coarsely tuned units (Edelman, 1998; Edelman & Duvdevani-Bar, 1997b) and its implementation as a computer model of recognition and categorization (Cutzu & Edelman, 1998; Edelman & Duvdevani-Bar, 1997a) provide a computational framework in which such findings can be interpreted in a straightforward fashion. Taken together, these developments in the study of object representation and recognition suggest that direct visualization of the internal representations may be easier than was previously thought. In this paper, we show how fMRI techniques can be used to investigate the internal representation of objects in the human visual cortex. Our initial results reveal that the activation of most voxels in object-related areas remains unaffected by a coarse scrambling of the natural images used as stimuli and that a map of the representation space of object categories in individual subjects can be derived from the distributed pattern of voxel activation in those areas.