Behavioural Brain Research 184 (2007) 47–56 Research report Is the cerebellum involved in the visuo-locomotor associative learning? Laura Mandolesi a,c,* , Maria Giuseppa Leggio b,c , Francesca Spirito b,c , Francesca Federico d,c , Laura Petrosini b,c a University of Naples “Parthenope”, Italy b Department of Psychology, University of Rome “La Sapienza”, Italy c IRCCS Fondazione Santa Lucia, Rome, Italy d University of Siena, Italy Received 14 March 2007; received in revised form 13 June 2007; accepted 26 June 2007 Available online 29 June 2007 Abstract 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. © 2007 Elsevier B.V. All rights reserved. Keywords: Discrimination task; Explorative strategies; Procedural components; Rat 1. Introduction Clinical and experimental evidence demonstrates that the cerebellum is involved in many forms of implicit learning [10,14,28,38,54]. The associative learning is an example of implicit learning where the subject has to learn about the rela- tionship between two stimuli or between a stimulus and a behaviour [16,19] is. While some clinical research has evidenced noticeable involvement of cerebellar networks in associative learning [6,12,34,59], other clinical and functional studies have Abbreviations: HCb, hemicerebellectomy; HCbed, hemicerebellectomized; C, Control * Corresponding author at: Centro Europeo di Ricerca sul Cervello (C.E.R.C.), Via del Fosso di Fiorano 65, 00143 Rome, Italy. Tel.: +39 06 501703077; fax: +39 06 501703324. E-mail address: laura.mandolesi@uniparthenope.it (L. Mandolesi). indicated that the cerebellum is not essential [9,11,56,57]. This latter finding is supported by a few experimental studies investi- gating the cerebellar role in associative learning. Past researches reported that pigeons with cerebellar cortical lesions exhibited few errors on a pre-operatively learned visual discrimination, but they took significantly longer to respond [38] and that in fish cerebellar activity is important for optimal discrimination per- formance [20,21]. Finally, cerebellar ablations have been found to interfere with visual discrimination in turtles and in lizards [52]. More recently, it has been reported that rats with lateral cerebellar lesions were reported to perform similarly to nor- mal animals in visual discrimination learning [18]. Monkeys with bilateral lesions of the lateral cerebellar nuclei were able to retain a pre-operatively learned conditional associative task [42]. Recently, Richter et al. [49] showed that the cerebellar involve- ment in associative learning depends on task features. They reported that patients with degenerative cerebellar pathologies 0166-4328/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.bbr.2007.06.014