Spatial arrangements of responses by cells in the cat visual cortex to light and dark bars and edges.

Detailed examination is made of the responses of visual cortical cells (area 17, border 17-18 and adjacent area 18) in the anaesthetized cat to stationary flashing bars and to bars (lines) and edges moving at their optimal velocities. Particular attention is given to the receptive field organization of cells in the simple family. While there is good general agreement between the main receptive field subregions revealed by stationary and moving stimuli, the responses to moving light and dark bars, supplemented by the responses to moving light and dark edges, provide a much more rapid, accurate and complete guide to the spatial organization of the receptive fields than do the response profiles to a stationary flashing bar. Moving light and dark bars between them generally reveal more subregions in the receptive fields of simple cells than is evident from the response profiles to a stationary flashing bar, particularly when the receptive fields have many subregions. In addition the responses to moving edges provide a rapid guide to spatial summation across the width of a subregion and the possible antagonistic effects of the next subregion in sequence. Two subclasses of cells in the simple family have been recognized: ordinary simple and fast simple cells. Two cell classes (A-cells and silent periodic cells) having properties intermediate between simple and complex types are discriminated and their properties described.