Introduction

The primary visual cortex (V1) represents the first cortical relay of visual input. Basic aspects of an object are initially analyzed at this level. Similarly, somatosensory information is initially processed in the primary somatosensory areas. The central nervous system (CNS) integrates information originating in different modalities. Such integration is thought to occur in association areas of the cerebral cortex (Hadjikhani & Roland, 1998; Mesulam, 1998). However, recently acquired evidence challenges this assumption. For example, the perception of colors is possible even after damage to V1. It has been proposed that a pathway connecting the pulvinar with V4 could mediate such transfer, bypassing V1 (for a review, see Zeki, 2001). It is likely, therefore, that integration of multisensory information could take place at different levels of the nervous system.