Spatial organization of subregions in receptive fields of simple cells in cat striate cortex as revealed by stationary flashing bars and moving edges.

For each of 74 simple striate cells a quantitative analysis was made of the width dimensions and spatial arrangements of the subregions responding either at light on (ON subregion) or at light off (OFF subregion). It was concluded that every cell has at least two and no more than four subregions. Cells with two subregions (57%) were much more commonly encountered than those with three (32%) or four (11%). For most cells adjacent subregions were significantly overlapped, the region of overlap responding both at light on and at light off. In the case of cells with two subregions, the overlap averaged 32% of the overall width of the two subregions. Despite the degree of the overlap, there was, on this basis, still a large measure of discrimination between cells in the simple family and those in the B-cell and complex families. In general the receptive field profiles of cells with three and four subregions were only marginally wider than those with only two subregions. In any given receptive field, the subregions tend to be roughly equal in width so that, in cells with four subregions, the subregions are, on the average, distinctly narrower than they are in cells with only two. Hypercomplex I cells tend to have receptive fields with three and four subregions much more commonly than simple cells and these cells are encountered much more frequently in cortical cell laminae 2, 3 and 4 than in lamina 6. In lamina 6 most of the cells in the simple family have receptive fields with only two subregions. The width dimensions and spatial sequences of the response peaks to moving light and dark edges were quantitatively analyzed in response profiles prepared from 82 cells. In general, for any given receptive field, the response peaks to moving edges have a one-to-one correspondence with the subregions to a stationary flashing bar. When this is not the case, the tendency is for the number of response peaks to edges to be less than the number of subregions rather than more.