Neuronal Remodeling After Early Cerebellar Hemispherectomy in Rats
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Numerous experimental studies have demonstrated that brain lesions at early stages of maturation lead to a greater degree of neuronal rearrangement than such lesions at adulthood. These morphological changes have been regarded as the substrate for a greater compensational capacity of the immature brain. Margaret Kennard has shown that after unilateral removal of the motor and premotor cortex in newly born rhesus monkeys no motor disturbances developed, while after such lesions at later ages monkeys remained impaired (Kennard 1942). However, more recent experiments with lesions of other brain areas raised doubts that compensation is always complete. On the contrary, even bizarre behavioral anomalies may occur, particularly after lesions at young ages. Schneider and Jhaveri (1974), for instance, made unilateral lesions in the optic tectum of Syrian hamsters at birth. On testing, these animals as adults carried out abnormal head movements away from visual stimuli. In addition, the authors demonstrated retinotectal fibers recrossing to the remaining colliculus which might explain these abnormal movements. These two examples may illustrate the complicated relationship between neuronal remodeling after early lesions and the capacity of functional compensation.
KeywordsSensorimotor Cortex Cerebellar Nucleus Pontine Nucleus Inferior Olivary Nucleus Interpositus Nucleus
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