A revised view of sensory cortical parcellation.
Traditional cortical parcellation schemes have emphasized the presence of sharply defined visual, auditory, and somatosensory domains populated exclusively by modality-specific neurons (i.e., neurons responsive to sensory stimuli from a single sensory modality). However, the modality-exclusivity of this scheme has recently been challenged. Observations in a variety of species suggest that each of these domains is subject to influences from other senses. Using the cerebral cortex of the rat as a model, the present study systematically examined the capability of individual neurons in visual, auditory, and somatosensory cortex to be activated by stimuli from other senses. Within the major modality-specific domains, the incidence of inappropriate (i.e., nonmatching) and/or multisensory neurons was very low. However, at the borders between each of these domains a concentration of multisensory neurons was found whose modality profile matched the representations in neighboring cortices and that were able to integrate their cross-modal inputs to give rise to enhanced and/or depressed responses. The results of these studies are consistent with some features of both the traditional and challenging views of cortical organization, and they suggest a parcellation scheme in which modality-specific cortical domains are separated from one another by transitional multisensory zones.
Wallace
Mark T
MT
Department of Neurobiology and Anatomy, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA. mwallace@wfubmc.edu
Ramachandran
Ramnarayan
R
Stein
Barry E
BE
D000818:Animals; D002540:Cerebral Cortex / Q000166:cytology / Q000502:physiology*; D008297:Male; D008959:Models, Neurological; D019579:Neocortex / Q000166:cytology / Q000502:physiology; D009474:Neurons / Q000502:physiology; D010465:Perception / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D013997:Time Factors