EARLY CEREBELLAR LESIONS IMPAIR EYEBLINK CONDITIONING IN DEVELOPING RATS - DIFFERENTIAL-EFFECTS OF UNILATERAL LESIONS ON POSTNATAL DAY-10 OR DAY-20

Experiment 1 demonstrated that the ipsilateral cerebellar hemisphere i s essential for the acquisition of eyeblink conditioning in infant rat s and that cerebellar lesions given on Postnatal Day 10 (PND10) produc ed deficits in eyeblink conditioning when given to either hemisphere. For both hemispheres, lesions that were restricted to the cerebellar c ortex produced less severe deficits than lesions that included the dee p nuclei. Experiment 2 showed that the age at which the cerebellar les ions occurred determined whether damage to the contralateral cerebella r hemisphere impaired conditioning. Lesions of either the ipsilateral or contralateral hemisphere that included the deep nuclei disrupted ey eblink conditioning when given on PND10. In contrast, when lesions wer e given on PND20, ipsilateral lesions that included the deep nuclei ab olished conditioning, while the same lesion given to the contralateral hemisphere had no effect.