Seeing does not mean processing: Where we look and the visual information we rely on change independently as we learn to walk.

Abstract

People use vision to inform motor control strategies during walking. With practice performing a novel target stepping task, people gradually shift their gaze farther ahead, transitioning from watching their feet contact the target to looking for future targets. The shift in gaze focus suggests that the role of vision during the task changes from emphasizing feedback to feedforward control. The present study examines whether the change in visual fixation location is accompanied by a similar change in reliance upon visual information. 12 healthy young adults practiced stepping on projected moving targets during treadmill walking. Periodically, participants’ visual reliance was probed by hiding the stepping targets when they would inform feedback or feedforward motor control strategies. We calculated visual reliance as the increase in step error between a limited vision condition and the full vision condition. We hypothesized that with practice, participant reliance on feedback information would decrease and their reliance on feedforward information would increase. Against our hypothesis, we found that participants became significantly more reliant on feedback visual information with practice (p<0.001) but their reliance on feedforward visual information did not change (p=0.07). Participants’ reliance changed despite them looking significantly farther ahead with practice (p<0.001). Together, these results suggest that participants fixated on feedback information less, possibly due to more efficient processing. However, the increased efficiency did not reduce their reliance upon feedback information as removing feedback visual information significantly worsened performance. These findings provide important context for how the role of vision in controlling walking changes with practice.