Is the cerebellum involved in the visuo-locomotor associative learning?

The role played by cerebellar circuits in visuo-motor associative learning is still unclear. The aim of the present study was to analyse cerebellar involvement using a visuo-locomotor associative learning paradigm that did not require spatial competences. Hemicerebellectomized (HCbed) and Control rats were tested in a visual discrimination task. First, both groups of rats had to learn that a reward was associated with an object that had a specific colour and shape (Experiment 1). Then, the shape but not the colour of the rewarded object was modified to verify whether the animals were able to transfer the rule of rewarding or whether they had to acquire a new association (Experiment 2). In the first sessions of the Experiment 1, HCbed animals displayed a tendency toward peripheral circling and a delay of about three sessions in reaching the criterion of correct choices compared to Controls. This delay has to be correlated to the need to overcome the procedural impairment elicited by the HCb. Once the HCbed animals put efficient procedural abilities into action, they exhibited a similar increase in percentages of successes from the fourth session onward as Controls. The results of Experiment 2 confirm the intact associative abilities of HCbed animals, as demonstrated by their progressive increase in successful associative responses, which, at the end of the transfer phase, were not significantly different from those of the Control group. The present findings indicate that the presence of a cerebellar lesion delays but does not prevent visuo-locomotor associative learning and that stimulus generalisation is performed without difficulty even in the presence of a cerebellar lesion. (C) 2007 Elsevier B.V. All rights reserved