The Effect of Spatial and Temporal Interactions on the Responses of Single Units in the Cat's Visual Cortex

Single unit recordings from the striate cortex of the cat were used to study information processing in the visual cortex. This was done in two steps: First, the proportions of units in the cortex responding to stimulus-on only, stimulus-off only, or both, were compared to the theoretical probability of similarly distributed responses, given a random selection of TV on-center and/or off-center fibers. It was shown that afferent input onto a cortical pyramidal neuron probably comes from only a few (three to six) individual fibers, forming parallel and relatively independent input/output (I/O) pathways. Second, by comparing the responses of cortical units to single and two-point stimulation, it was shown that interactions occur between neighboring neurons receiving nearby projections of the visual world. These interactions modulate the responses in the I/O pathways, effectively “tuning” the cells to respond selectively to a more specific stimulus configuration than would otherwise be required. The results of...