Analysis of the effects of operant conditioning on cortical unit response patterns

Abstract

Patterns of response to visual stimuli were studied in cells in cat visual cortex. Changes in these patterns were measured during an operant conditioning paradigm in which reinforcement (rewarding brain stimulation) was presented contingent upon the occurrence of a specific change in a cell's pattern of response. For half of the cells studied, frequency of reinforcement increased significantly during the conditioning procedure: in 26% of the cells, the increase was due to increased firing confined to the time segment specified by the contingency of reinforcement. Cells studied during a control procedure, in which reinforcement was delivered randomly, did not exhibit changes in response pattern. Statistical properties of each cell's preconditioning or baseline pattern of response, as reflected in peristimulus time histograms compiled on line, were analyzed. Modifiability of a cell's response pattern was significantly correlated with spontaneous discharge rate and also with the overall strength of the changes initially evoked in the cell's activity by the visual stimulus. Cells that exhibited specific conditioned changes had higher spontaneous rates and more complicated response patterns than cells that did not.