The Human Visual Cortex

Annu. Rev. Neurosci. 2004. 27:649–77 doi: 10.1146/annurev.neuro.27.070203.144220 Copyright c 2004 by Annual Reviews. All rights reserved

THE HUMAN VISUAL CORTEX
Kalanit Grill-Spector1 and Rafael Malach2
1

Annu. Rev. Neurosci. 2004.27:649-677. Downloaded from arjournals.annualreviews.org by Pontificia Universidad Javeriana on 09/17/09. For personal use only.

Department of Psychology andNeuroscience, Stanford University, Stanford, California 94305-2130; email: kalanit.grill-spector@stanford.edu 2 Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel; email: rafi.malach@weizmann.ac.il

Key Words functional magnetic resonance imaging (fMRI), visual perception, object and face recognition, retinotopic mapping I Abstract The discovery and analysis of corticalvisual areas is a major accomplishment of visual neuroscience. In the past decade the use of noninvasive functional imaging, particularly functional magnetic resonance imaging (fMRI), has dramatically increased our detailed knowledge of the functional organization of the human visual cortex and its relation to visual perception. The fMRI method offers a major advantage over other techniques appliedin neuroscience by providing a large-scale neuroanatomical perspective that stems from its ability to image the entire brain essentially at once. This bird’s eye view has the potential to reveal large-scale principles within the very complex plethora of visual areas. Thus, it could arrange the entire constellation of human visual areas in a unified functional organizational framework. Here wereview recent findings and methods employed to uncover the functional properties of the human visual cortex focusing on two themes: functional specialization and hierarchical processing.

INTRODUCTION
In the past decade the use of noninvasive functional imaging, particularly functional magnetic resonance imaging (fMRI), has dramatically increased our detailed knowledge of the functional organizationof the human visual cortex. Thus, more than a dozen putative human visual areas have been described using fMRI (Tootell 1996, 2003). The discovery and analysis of cortical visual areas are major accomplishments in visual neuroscience. The number, locations, and functional roles of these areas are important topics for continuing experimental studies of the human brain. In trying to account for themultiplicity of visual areas, two main principles have been suggested: hierarchical processing and functional specialization. Hierarchical processing proposes that visual perception is achieved via a gradual stagewise process in which information is first represented in a localized and simple form and, through a sequence of processes, is transformed into more
0147-006X/04/0721-0649$14.00

649650

GRILL-SPECTOR

MALACH

Annu. Rev. Neurosci. 2004.27:649-677. Downloaded from arjournals.annualreviews.org by Pontificia Universidad Javeriana on 09/17/09. For personal use only.

abstract, holistic, and even multimodal representations (DeYoe & Van Essen 1988). The second principle, functional specialization, proposes that specialized neural pathways exist that process informationabout different aspects of the visual scene. In particular the visual system may consist of parallel hierarchical sequences, or processing streams, that are specialized for a particular functional task. The dorsal stream, also referred to as the “where” (Mishkin et al. 1983) or “action” (Goodale et al. 1991) stream, has been associated with spatial localization (or visually guided action) and theventral “what” stream (Mishkin et al. 1983), which are involved in object and form recognition and are the best-known of the processing streams. Here we review recent findings and methods employed to uncover the functional properties of the human visual cortex, focusing on these two themes: functional specialization and hierarchical processing.

MAPPING THE HUMAN VISUAL CORTEX
In the macaque,...