1 Department of Psychology, Laboratory for Motor Learning, Cognitive Learning, and Neural Plasticity, Concordia University, 7141 Sherbrooke St. W., Science Pavilion SP-250, Montreal, Québec H4B 1R6, Canada. t_savion@alcor.concordia.ca

The present study assessed the effects of amount of practice and length of delay on the learning and retention of a timed motor sequence task. Participants learned to reproduce ten-element visual sequences by tapping in synchrony with the stimulus. Participants were randomly assigned to a varied-practice condition or a varied-delay condition. In the varied-practice condition, participants received either one, three, or six blocks of practice followed by a fixed 4-week delayed-recall. In the varied-delay condition, participants received three blocks of practice followed by a varied delay of either 3 days, or 2, 4, or 8 weeks. Learning was assessed by changes in accuracy, response variance, and percent response asynchrony. Our results showed that amount of practice per se did not affect learning and retention of the task. Rather, distribution of practice over several days was the most important factor affecting learning and retention. We hypothesize that passage of time is essential for a maximum benefit of practice to be gained, as the time delay may allow for consolidation of learning, possibly reflecting plastic changes in motor cortical representations of the skill. With regards to delay, our findings suggest that explicit and motoric components of a motor sequence are likely to be learned and maintained in separate but interacting systems. First, only the longest delay group showed decrements in percent correct, indicating that longer lengths of delay might hinder retrieval of explicit aspects of the task. Second, all groups showed a decrement in percent response asynchrony, suggesting that synchronization may be a more difficult parameter to maintain because it relies heavily on sensorimotor integration.