Representation of actions in rats: The role of cerebellum in learning spatial performances by observation

Experimental evidence demonstrates that cerebellar networks are involved in spatial learning, controlling the acquisition of exploration strategies wi thout blocking motor execution of the task, Action learning by observation has been considered somehow related to motor physiology, because it provide s a way of learning performances that is almost as effective as the actual execution of actions. Neuroimaging studies demonstrate that observation of movements performed by others, imagination of actions, and actual execution of motor performances share common neural substrates and that the cerebell um is among these shared areas. The present paper analyzes the effects of o bservation in learning a spatial task, focusing on the cerebellar role in l earning a spatial ability through observation. We allowed normal rats to ob serve 200 Morris water maze trials performed by companion rats. After this observation training, "observer" rats underwent a hemicerebellectomy and th en were tested in the Morris water maze. In spite of the cerebellar lesion, they displayed no spatial defects, exhibiting exploration abilities compar able to controls. When the cerebellar lesion preceded observation training, a complete lack of spatial observational learning was observed. Thus, as d emonstrated already for the acquisition of spatial procedures through actua l execution, cerebellar circuits appear to play a key role in the acquisiti on of spatial procedures also through observation. In conclusion, the prese nt results provide strong support for a common neural basis in the observat ion of actions that are to be reproduced as well as in the actual productio n of the same actions.