TIMED ACTIVE-AVOIDANCE LEARNING IN LURCHER MUTANT MICE

Lurcher mutant mice (+ /Lc) which exhibit a massive loss of neurons in the cerebellar cortex and in the inferior olivary nuclei were subject ed to an active avoidance learning task; the animals' avoidance respon se must occur within a small time window after a short or a long delay . The control mice needed a mean of 8.3 sessions of 10 trials (short d elay group) and of 11.8 sessions (long delay group) and showed good re tention after a 24 h interval. When subjected to the same number of se ssions, the + /Lc mice were unable to learn the timing task. However, a subgroup of lurcher mutants was able to learn after a high number of sessions (25.4 sessions as a mean). There was no intergroup differenc e in the standard version of one-way active avoidance. These results i ndicate that the cerebellar cortex is involved in time processing duri ng active avoidance. The cerebellum may be part of a loop including th e cerebral cortex known to be involved in time perception. An alternat ive explanation is that the cerebellar mutant animals had persevering tendencies acquired during performance of the one-way avoidance task. (C) 1998 Elsevier Science B.V. All rights reserved.