CONCOMITANT SENSITIVITY TO ORIENTATION, DIRECTION, AND COLOR OF CELLS IN LAYER-2, LAYER-3, AND LAYER-4 OF MONKEY STRIATE CORTEX

The receptive field properties of cells in layers 2, 3, and 4 of area 17 (V1) of the monkey were studied quantitatively using colored and broad-band gratings, bars, and spots. Many cells in all regions studied responded selectively to stimulus orientation, direction, and color. Nearly all cells (95%) in layers 2 and 3 exhibited statistically significant orientation preferences (biases), most exhibited at least some color sensitivity, and many were direction sensitive. The degree of selectivity of cells in layers 2 and 3 varied continuously among cells; we did not find discrete regions containing cells sensitive to orientation and direction but not color, and vice versa. There was no relationship between the degree of orientation sensitivity of the cells studied and their degree of color sensitivity. There was also no obvious relationship between the receptive field properties studied and the cells' location relative to cytochrome oxidase-rich regions. Our findings are difficult to reconcile with the hypothesis that there is a strict segregation of cells sensitive to orientation, direction, and color in layers 2 and 3. In fact, the present results suggest the opposite since most cells in these layers are selective for a number of stimulus attributes.