Cerebellar contribution to spatial navigation: new insights into potential mechanisms.

The contribution of the cerebellum to the non-motor aspects of spatial navigation is now established, but the mechanisms of its participation remain unclear. The L7-PKCI mouse model, in which inhibited PKC activity suppresses parallel fiber-Purkinje cell long-term depression (LTD), provides the opportunity to study their spatial abilities in the absence of any motor impairment. L7-PKCI mice are deficient in the spatial but not the cued version of the watermaze task. Their performances are preserved when alleys guide their trajectories in the starmaze task, suggesting that cerebellar PKC-dependent mechanisms are required for the production of an optimal trajectory toward a goal. Furthermore, electrophysiological recordings in freely moving L7-PKCI mice revealed that their hippocampal place cell properties are affected when they have to rely on self motion information: in the absence of external information as well as in a conflicting situation between self-motion and external information. This suggests that the cerebellum is involved in the processing of self-motion information and is required for the construction of the spatial representation in the hippocampus.