Representation of Human Body Stimuli within the Human Visual System

Abstract

The human body is a unique and complex visual stimulus, the accurate representation of which is critical for social interaction/communication, acquisition of complex skills, and even basic survival. In a series of studies, using behavioral and neuroimaging techniques, the visual representation of some of the basic features of body perception (e.g., individual parts and their relationships) were explored. First, using a behavioral adaptation paradigm, sensitivity to the relative proportions between limbs was explored. We found that human observers were highly sensitive to relative limb proportion and further demonstrated that this effect appears to depend on body and limb specific mechanisms. Second, an fMRI experiment was used to assess the sensitivity of body-selective cortical areas to the spatial configuration of pairs of limb parts. We found that activity in body-selective areas systematically varies with the typicality of their spatial configuration. Finally, advanced sub-millimeter fMRI techniques were used investigate whether body-selective cortex contained subordinate representations of body stimuli (e.g., their individual parts). We found that the body-selective area of the right extrastriate cortex yields the highest responses to hands above all other stimuli. Furthermore, advanced spatial mapping techniques revealed that this cortical area contains spatially consistent clusters of voxels which preferentially respond to hands. Taken together, these results help to clarify how individual body parts and the relationships between them are represented within the human visual system.