Effects of paleocerebellar lesions on DRL performance in the albino rat

Normal rats and rats with paleocerebellar lesions were trained to bar press for food on continuous reinforcement (CRF) and differential reinforcement of low response rates (DRL) schedules. The animals with lesions showed normal acquisition of the CRF schedule, but they exhibited a marked deficit on the DRL task. This deficit was related to overresponding which appeared to result from an inability to inhibit the response, rather than from a dysfunction in timing ability or motor capacity. The DRL deficit, however, was overcome by the introduction of a salient stimulus object (wood block) into the operant situation. Although no explicit reinforcement contingencies were placed on interaction with the stimulus object, it appeared that the wood block facilitated the development of "collateral" behaviors that served to mediate the DRL interval. These results are consistent with the suggestion that the cerebellum may contribute to the sequential organization of complex behaviors.