“The cerebral hemispheres are the same but different.”
Despite the similarity in structure, the hemispheres of the human brain have somewhat different functions. A traditional view of hemispheric organization asserts that there are independent and largely lateralized domain-specific regions in ventral occipitotemporal (VOTC), specialized for the recognition of distinct classes of objects. In this talk, I will offer an alternative account of the organization of the hemispheres, with a specific focus on face and word recognition. This alternative account relies on three computational principles: distributed representations and knowledge, cooperation and competition between representations, and topography and proximity. The crux of the account is that visual recognition results from a network of regions with graded functional specialization, which is distributed across both hemispheres. Specifically, the claim is that face recognition, which is acquired relatively early in life, is processed by VOTC regions in both hemispheres. Once literacy is acquired, word recognition, which is co-lateralized with language areas, primarily engages the left VOTC and, consequently, face recognition is primarily, albeit not exclusively, mediated by the right VOTC. I will present psychological and neural evidence from a range of studies conducted with normal adults and children, as well as from cases with neuropsychological deficits and from cases with hemispherectomy, and will also consider evidence that seems incompatible with this account. Last, I will offer suggestions for future investigations whose findings may further refine this account and enhance our understanding of the functions of the cerebral hemispheres.