Changes in task parameters during walking prism adaptation influence the 1 subsequent generalization pattern

42 An understanding of the transfer (or generalization) of motor adaptations between legs and 43 across tasks during walking has remained elusive due to limited research and mixed results. Here, 44 we asked whether stepping sequences or task constraints introduced during walking prism 45 adaptation tasks influence generalization patterns. Forty subjects adapted to prism glasses in 46 precision walking or obstacle avoidance tasks that required a specific stepping sequence to the 47 centre of two/three targets or laterally over an obstacle. We then tested for generalization, 48 reflected by aftereffects in the non-adapted task. Our previous study using these tasks found that 49 only one leg generalized. Here, we reversed the stepping sequence and found that only the 50 opposite leg generalized in the subject group that adapted in a precision walking task. The 51 combination of stepping sequence and direction of prism shift caused subjects in two groups to 52 collide with the obstacle early during adaptation, thus making the step prior to going over the 53 obstacle more important. Both legs subsequently generalized. A fourth subject group experienced 54 a three-target precision walking task resulting in a balanced right-left, left-right stepping 55 sequence meant to induce bilateral generalization. While only one leg generalized, foot 56 placement aftereffects before stepping over the obstacle would have caused subjects to collide 57 with it. Together with our previous study, the results suggest a contribution of stepping sequence 58 during the adapted task on generalization patterns, likely driven by proprioceptive feedback. The 59 results also support the idea that negative consequences during adaptation and/or perceived threat 60 can influence generalization. 61