Role of the cerebellum in an avoidance conditioning task in the rat.

Adult DA/HAN strain male rats were submitted to an avoidance conditioning procedure. They were divided into two experimental groups, the animals being either conditioned (COC group) or not (NOC group) before cerebellectomy, and two control groups, the animals being either intact (C group) or sham-operated (SO group). Although the NOC rats could be conditioned successfully and the cerebellum is not absolutely necessary for the avoidance conditioning achievement, their scores were significantly lower than the preoperative scores of COC rats. Moreover, the scores of NOC rats (postoperative scores) were significantly lower than the postoperative scores of COC animals, suggesting that the preoperative conditioning makes the postoperative conditioning easier. At last, comparing postoperative scores of COC rats with those obtained by C and SO rats when given the retrieval test and comparing preoperative and postoperative scores in COC animals show that retention of the initial (preoperative) conditioning is partly abolished by the cerebellectomy. Histological controls demonstrated that the entire cerebellum except for the flocculus and the nodulus was removed. These results strongly suggest that the cerebellum is involved in the memory processes that sustain the avoidance conditioning.