Neonatal Versus Adult Hemicerebellectomy: A Behavioral and Anatomical Analysis

Abstract

In spite of several reports on infant lesion effects, the degree to which brain damage occurring early in life results in sparing or greater recovery of motor function than that seen after comparable damage in adults is still uncertain (Schneider 1979). On one hand, following neonatal spinal transection (Bregman and Goldberger 1983) or cortical ablations (D’Amato and Hicks 1980), there is greater recovery of some postural reflexes when compared with the same lesions sustained in adulthood. On the other hand, coexistent with these examples of greater recovery, are examples of equivalent or even greater deficits or poorer motor performances (Finger et al. 1978). Namely, it has been reported that neonatally hemicerebellectomized rats exhibit a more impaired locomotion in comparison with rats hemicerebellectomized in adulthood (Gramsbergen and IJkema-Paassen 1984). These conflicting findings are complicated by the influence of normal development on motor behavior, by the stage of maturity of the pathways at the time of the lesion, and finally by the nature of the motor behaviors, since different aspects of the same behavior may respond differently to the same lesion. Considering these numerous variables, this study is focused on comparing various motor behaviors of rats hemicerebellectomized neonatally with those of rats hemicerebellectomized at weaning or in adulthood, to analyze the problem of whether cerebellar lesions made during different maturation stages provoke different effects. Particular care was taken to obtain adequate experimental conditions for comparisons of the three age-at-lesion groups; all cerebellar lesions were very similar, and repeated and extremely fine assessments of motor function using similar tests were performed at comparable long periods after lesion.