IMPAIRED MOTOR LEARNING-PERFORMANCE IN CEREBELLAR EN-2 MUTANT MICE

Mice homozygous for a null mutation in their En-2 gene exhibit cerebel lar neuroanatomical alterations including absence and misplacements of specific fissures and size reduction. The present study investigated cerebellar function by comparing the behavior of age-matched homozygou s and heterozygous En-2 mutant and wild-type mice. Motor function of t he mutants was found normal in several situations. Habituation to nove lty in the open field was not significantly different in mutants. Howe ver, in a motor learning paradigm, the rotating rod, the performance o f homozygous mutant mice improved significantly less than that of the heterozygous mice which were also significantly impaired compared to w ild-type mice. Unlike other cerebellar mutants in which severe motor o r sensory defects are obvious, the En-2 mouse model offers a unique to ol to study the role of cerebellum in complex behavioral phenomena, in cluding motor learning, without confounding effects.