Hemispheric organization in humans: two hemispheres, one mind

The study of cerebral organization, including differences in hemispheric structure and function, have a longstanding history in Cognitive Neuroscience. With regard to visual processing, one traditional view of hemispheric organization asserts that there are independent and largely lateralized domain-specific regions in ventral occipitotemporal cortex, which are specialized for the recognition of distinct classes of objects. In this talk, I will offer an alternative account of the organization of the hemispheres, and their contribution to complex pattern recognition. Drawing on evidence from studies of the visual system in health and disease (normal adults and children, individuals with focal neuropsychological deficits and cases with hemispherectomy or lobectomy), I will propose that the hemispheric arrangement emerges through the interaction of three computational principles: distributed representations and knowledge, cooperation and competition between representations, and a topographic bias favoring spatial proximity. The crux of the account is that visual recognition results from the interactive engagement of a network of regions, which is distributed within and across both hemispheres, and which evince graded functional specialization. Data will be used to test predictions such as specific collaborative and competitive synergies of hemispheric bias that play out over the course of development and the extent to which a single hemisphere might suffice for recognition. Last, I will lay out open questions which will, undoubtedly, occupy the field into the future.