IMPAIRED MOTOR-SKILLS ON STATIC AND MOBILE BEAMS IN LURCHER MUTANT MICE

The cerebellum plays a role in various sensorimotor learning tasks. Th e purpose of the present studies was to evaluate sensorimotor skills i n a spontaneous mouse mutant with cerebellar cortical atrophy. Lurcher mutant mice, characterized by massive losses of cerebellar granule ce lls and Purkinje cells, were assessed on two static beams varying in w idth and on an accelerating rotorod. On the static beams, lurcher muta nts were deficient in stable positioning while immobile. Contrary to n ormal mice, they retreated backwards involuntarily and clung off-balan ce to the side of the beams. However, lurcher mutants were not deficie nt in segment crossings, body turns, latencies before crossing the fir st segment, and time spent in motion. There was an improvement over da ys in static stable positioning on both beams. On the rotorod, althoug h lurcher mutants fell sooner and were inferior to controls in maximal speed of rotation achieved, there was an improvement on both measures across days. Moreover, retention of this motor skill was normal. Thes e results indicate that, although lurcher mutants are limited in their capacity to execute motor coordination tasks, postural sensorimotor l earning is not abolished in the absence of cerebellar cortical output neurons.