Use of explicit processes during a visually guided locomotor learning task predicts 24-hour retention after stroke
Implicit and explicit processes can occur within a single locomotor learning task. The combination of these learning processes may impact how individuals acquire/retain the task. Because these learning processes rely on distinct neural pathways, neurologic conditions may selectively impact the processes that occur, thus, impacting learning and retention. Thus, our purpose was to examine the contribution of implicit and explicit processes during a visually guided walking task and characterize the relationship between explicit processes and performance/retention in stroke survivors and age-matched healthy adults. Twenty chronic stroke survivors and twenty healthy adults participated in a 2-day treadmill study. Day 1 included Baseline, Acquisition1, Catch, Acquisition2, and Immediate Retention phases and Day 2 included 24-hour Retention. During acquisition phases, subjects learned to take a longer step with one leg through distorted visual feedback. During Catch and retention phases, visual feedback was removed and subjects were instructed to walk normally (Catch) or how they walked during the acquisition phases (retention). Change in step length from Baseline to Catch represented implicit processes. Change in step length from Catch to the end of Acquisition2 represented explicit processes. A mixed ANOVA found no difference in the type of learning between groups (p=0.74). There was a significant relationship between explicit processes and 24-hour retention in stroke survivors (r=0.47, p=0.04), but not in healthy adults (r=0.34, p=0.15). These results suggest that stroke may not affect the underlying learning mechanisms used during locomotor learning, but that these mechanisms impact how well stroke survivors retain the new walking pattern.