STRUCTURAL STABILITY WITHIN THE LATERAL CEREBELLAR NUCLEUS OF THE RATFOLLOWING COMPLEX MOTOR LEARNING

Complex motor learning, but not mere motor activity, has been previous ly shown to induce structural modifications within the cerebellar cort ex. The present experiment examined whether similar changes occur with in one of the primary output targets of the region of the cerebellar c ortex in which these structural changes were described, the lateral ce rebellar nucleus (LCN; dentate nucleus). Adult female rats were random ly allocated to one of three training conditions. Acrobatic condition (AC) rats were trained to complete a complex motor learning task consi sting of a series of elevated obstacles while motor control (MC) condi tion 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 micros copy were used to obtain estimates of synapse number and postsynaptic density (PSD) length within the LCN. Results showed that neither synap se number nor PSD length was significantly altered as a function of tr aining condition. These results indicate that complex motor skill lear ning is associated with structural plasticity within the cerebellar co rtex and with structural stability within the lateral cerebellar nucle us. (C) 1998 Academic Press.