Real time operations of the cerebellar cortex.

This manuscript reviews a series of experiments which support the notion that the cerebellum and more specifically the cerebellar cortex is principally involved in real time operations required for the regulation of coordinated motor activity. Experiments are reviewed which illustrate: (1) that the climbing fiber inputs to Purkinje cells can induce a short-lasting enhancement of their responses to mossy fiber-granule cell-parallel fiber inputs, (2) that the cerebellum is not essential for the acquisition and performance of the classically conditioned nictitating membrane reflex (NMR) of the rabbit, and (3) that the observations resulting from the microinjection of lidocaine and multiple single unit recordings within the brainstem support the notion that cell populations in this region may participate in establishing the modifications in neuronal interactions required for the acquisition of the conditioned NMR. In addition, preliminary data are shown comparing the capacity of a normal subject and a patient with a massive ipsilateral cerebellar stroke to learn certain tracing tasks and to redraw these learned tracing movements 90 degrees to the orientation of the original image. The data support the notion that the cerebellum is essential, not for the initial learning of the tracing movement, but rather for performing the learned movement with the required rotation of the original image.