Integration of Motor and Visual Information in the Dentate (lateral) Nucleus of Cerebellum During Locomotion

The dentate (lateral) nucleus (DN) of the cerebellum is one of the major sources of afferent input to the ventrolateral (VL) thalamus, and further to the motor cortex. Signals conveyed via this pathway are essential for neural control of movements, including accurate vision-guided stepping on complex terrain. The neuronal mechanisms underlying visual control of steps are not well understood. The goal of this study was to elucidate the integration of motor and visual information in the DN during locomotion on complex terrain by characterizing the components of DN activity that reflect overall locomotion movement, components related to visual guidance of feet to desired locations, and the integration of the two. Experiments were conducted on chronically implanted cats using an extracellular single-neuron recording technique. We found that during locomotion on a flat surface, a task that does not require visual control of feet placement, 63% of neurons discharged one activity burst per stride, while 19% had two bursts. Upon transition to vision-guided stepping on crosspieces of a horizontally placed ladder, the firing of 88% of neurons changed: either in the phase (63% neurons), depth of stride-related modulation (59%), firing rate (54%), and/or temporal precision (30%). We describe several ways by which motor and visual information needed for accurate feet placement on complex surface is integrated in the DN.