The cerebellum and perceptual learning

Evidence from the past two decades has clearly implicated the cerebellum in cognition, but its exact contribution remains unclear. In the motor domain, where the cerebellum explicates its main function, it is well known that it conveys a specific contribution, which is learning. According to the homogenous repetition of its microcircuitry, we hypothesized that even in cognition the cerebellum may play the same specific role it has in the motor domain, namely learning. In order to test this hypothesis we developed a computerized behavioral paradigm to unveil cognitive learning in the visuospatial functions. The task consisted in the motion trajectory extrapolation of a visual target, requiring for the subjects the ability to build an internal model of the moving pattern of the ball. The test was applied on seven normal subjects, five cerebellar patients and five control subjects. Patients showed a deficit both in the rate and in the amount of learning as compared to control subjects. Since among the forms of motor learning the one which more exquisitely depends on the cerebellum is motor adaptation, the ability to finely adjust motor commands to compensate for perturbations, we performed a second experiment in order to investigate whether the cerebellum could play an analogous function within perception, allowing perceptual adaptation of the internal model of the moving pattern of the stimulus in response to perturbed conditions. The test was applied on six normal subjects, five cerebellar patients and five control subjects. Patients showed an impaired adaptation as compared to control subjects, suggesting not only that even in cognition the cerebellum is responsible for learning, but also that it supports the same specific form of learning it is responsible for in the motor domain, namely adaptation. Therefore it derives that the cerebellum may operate the same computational function, as we could assume considering its structural homogeneity, which is constant regardless the cerebral cortical areas to which the cerebellum is connected.