Catching falling objects: the role of the cerebellum in processing sensory–motor errors that may influence updating of feedforward commands. An fMRI study

The human motor system continuously adapts to changes in the environment by comparing differences between the brain's predicted outcome of a certain behavior and the observed outcome. This discrepancy signal triggers a sensory-motor error and it is assumed that the cerebellum is a key structure in updating this error and associated feedforward commands. Using fMRI, the aim of the present study was to determine the main cerebellar structures that are involved in the processing of sensory-motor errors and in updating feedforward commands when simply catching a falling ball without displacement of the hand. Subjects only grasped the ball with their fingers when receiving it in their hand. By contrasting functional imaging signal obtained in conditions in which it was possible and impossible to predict the weight of the ball, we aimed to highlight sensory-motor error processing which we expected to be more marked in the conditions without prediction (less accurate feedforward process or more important feedback corrections) with respect to conditions with prediction (more accurate feedforward process or less important feedback corrections). When catching a falling ball and the possibility of prediction about the ball weight was manipulated, our results showed that both the right and left cerebellum is engaged in processing sensory-motor errors. It may also be involved in updating feedforward motor commands, perhaps on a trial by trial basis. In addition, when subjects were blindfolded, we observed a similar network but centered in a more anterior portion of the right cerebellum and we noted the presence of a cerebellar-thalamo-prefrontral network that may be involved in cognitive prediction (rather than sensory prediction) about ball weight.