Triple Dissociation of Faces, Bodies, and Objects in Extrastriate Cortex

Neuroscientists have long debated whether focal brain regions perform specific cognitive functions [1-5], and the issue remains central to a current debate about visual object recognition. The distributed view of cortical function suggests that object discrimination depends on dispersed but functionally overlapping representations spread across visual cortex [6-8]. The modular view claims different categories of objects are discriminated in functionally segregated and specialized cortical areas [9-11]. To test these competing theories, we delivered transcranial magnetic stimulation (TMS) over three adjacent functionally localized areas in extrastriate cortex. In three experiments, participants performed discrimination tasks involving faces, bodies, and objects while TMS was delivered over the right occipital face area (rOFA) [12], the right extrastriate body area (rEBA) [13], or the right lateral occipital area (rLO) [14]. All three experiments showed a task selective dissociation with performance impaired only by stimulation at the site selective for that category: TMS over rOFA impaired discrimination of faces but not objects or bodies; TMS over rEBA impaired discrimination of bodies but not faces or objects; TMS over rLO impaired discrimination of objects but not faces or bodies. The results support a modular account in which category-selective areas contribute solely to discrimination of their preferred categories.