Role of the cerebellum in the ontogenesis of the equilibrium behavior in the young rat: a behavioral study.

Young cerebellectomized and control DA/HAN strained rats, one day to 1 month old, were submitted to an equilibrium test. Cerebellectomized animals, operated when 10-, 20- or 24-day-old, were either trained-operated-trained (trained every day before and after cerebellectomy), naïve-operated-trained (cerebellectomized while naïve and trained every day after the operation), or naïve-operated-naïve (tested at one given day after the operation). Control rats were either trained-controls (trained every day) or naïve-controls (tested at a given day). Relevant comparisons show that (1) in control rats, the maturation of the equilibrium behavior does not depend on a specific training, at least to a great extent; however, training increases the rate of acquisition of the maximal score. (2) Rats cerebellectomized at day 10 and trained after cerebellectomy only are not able to learn a given motor pattern, while rats cerebellectomized by the 20th or 24th day are; however, their scores are always lower than those of control animals trained from the same age. Cerebellectomy alters the ontogenesis of the equilibrium behavior more especially as the operation is early. (3) Impairments of the equilibrium behavior after cerebellectomy can be explained by both motor disorders and learning processes deficiency. (4) Preoperative training counterbalances the effects of cerebellectomy in improving postoperative scores only when the cerebellum is removed at day 24. From these results it can be concluded that, in the rat, the cerebellum is involved in the learning processes that sustain the ontogenesis of the equilibrium behavior as it is in other motor learning mechanisms.