SELECTIVE SYNAPTIC PLASTICITY WITHIN THE CEREBELLAR CORTEX FOLLOWING COMPLEX MOTOR SKILL LEARNING

Complex motor skill learning, but not mere motor activity, leads to an increase in synapse number within the cerebellar cortex. The present experiment used quantitative electron microscopy to determine which sy napse types were altered in number. Adult female rats were allocated t o either an acrobatic condition (AC), a voluntary exercise condition ( VX), or an inactive condition (IC). AC animals were trained to travers e an elevated obstacle course requiring substantial motor coordination to complete. VX animals were housed with unlimited access to running wheels and IC animals received no motor training but were handled brie fly each day. Results showed the AC animals to have significantly more parallel fiber to Purkinje cell synapses than both the VX and IC anim als. No other synapse type was significantly altered. Thus, the learni ng-dependent increase in synapse number observed within the cerebellar cortex is accomplished primarily through the addition of parallel fib er synapses. (C) 1998 Academic Press.