Besides the basal ganglia, the cerebellum also has profound influences on motor function. Major cerebellar outflow paths converge on the ventral anterior and ventral lateral nuclei of the thalamus, and hence, these nuclei serve as a coordination center for the basal ganglia and cerebellar inputs to the cortex. Similar to the basal ganglia, the cerebellum influences the pyramidal system primarily through thalomocortical projections, and when cerebellar lesions occur, patients are poorly coordinated but are not weak. The cerebellar system, however, functions differently from the basal ganglia in that it has its own direct afferent paths from the entire cortex, as well as the spinal cord. The cerebellum appears to be important for rapid corrections of gross motor movements, whereas the basal ganglia affect more complex motor controls. As such, the prototype of a cerebellar lesion is sloppy execution of simple motor tasks but without the superimposition of abnormal involuntary movements (see Chapter .17 ).
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