Structural stability within the lateral cerebellar nucleus of the rat following complex motor learning.

Complex motor learning, but not mere motor activity, has been previously shown to induce structural modifications within the cerebellar cortex. The present experiment examined whether similar changes occur within one of the primary output targets of the region of the cerebellar cortex in which these structural changes were described, the lateral cerebellar nucleus (LCN; dentate nucleus). Adult female rats were randomly allocated to one of three training conditions. Acrobatic condition (AC) rats were trained to complete a complex motor learning task consisting of a series of elevated obstacles while motor control (MC) condition animals were forced to traverse a flat obstacle-free runway equal in length to the AC task. Inactive condition (IC) animals received no motor training. Unbiased stereological techniques and electron microscopy were used to obtain estimates of synapse number and postsynaptic density (PSD) length within the LCN. Results showed that neither synapse number nor PSD length was significantly altered as a function of training condition. These results indicate that complex motor skill learning is associated with structural plasticity within the cerebellar cortex and with structural stability within the lateral cerebellar nucleus.