DIFFERENTIAL ROLES OF CEREBELLAR CORTEX AND DEEP CEREBELLAR NUCLEI INLEARNING AND RETENTION OF A SPATIAL TASK - STUDIES IN INTACT AND CEREBELLECTOMIZED LURCHER MUTANT MICE

Lurcher mutant mice (+/Lc) exhibit a massive loss of neurons in the ce rebellar cortex and the inferior olivary nucleus, while deep cerebella r nuclei are essentially intact. To discriminate the relative particip ation of the cerebellar cortex and deep structures in learning and mem ory, 3 to 6-month-old +/Lc mice were subjected to a spatial learning t ask derived from the Morris water escape. They were able to learn to e scape as well as their strain-matched controls (+/+). Seven days later , their scores showed that they had memorized the spatial environment but not as accurately as +/+ mice. Cerebellectomy before training did not significantly alter the escape learning capabilities of either gro up, whereas cerebellectomy performed after learning completely abolish ed retention in +/+, as well as in Cnc, mice. These results suggest th at the cerebellum, although not necessary for learning a spatial task, plays a crucial role in its retention, and that the storing structure of spatial information differs in +/+ and +/Lc mice.