The Journal of Neurophysiology Vol. 88 No. 4 October 2002, pp. 2163-2166
Copyright ©2002 by the American Physiological Society

RAPID COMMUNICATION

No ON-OFF Maps in Supragranular Layers of Ferret Visual Cortex

Center for Neuroscience, University of California, Davis, California 95616

Chapman, Barbara and Imke Gödecke. No ON-OFF Maps in Supragranular Layers of Ferret Visual Cortex. J. Neurophysiol. 88: 2163-2166, 2002. Primary visual cortex contains functional maps of a number of stimulus properties including ocular dominance, orientation, direction, color, and spatial frequency. These maps must be organized with respect to each other and to a single continuous retinotopic map of visual space such that each stimulus parameter is represented at each point in space. In the ferret, geniculo-cortical inputs to cortical layer IV are segregated into ON- and OFF-center patches, suggesting the possibility that there might be an additional cortical map in this species. We have used optical imaging of intrinsic signals to search for ON-OFF maps in ferret visual cortical cells and have found none. This suggests that the high degree of ON-OFF segregation seen subcortically in the ferret may play a role in the development of visual cortical receptive fields rather than in adult cortical function.