Visuomotor errors drive step length and step time adaptation during ‘virtual’ split-belt walking: the effects of reinforcement feedback

• Published in: Experimental brain research Vol. 240; no. 2; pp. 511 - 523
• Main Authors: Sato, Sumire, Cui, Ashley, Choi, Julia T.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.02.2022; Springer; Springer Nature B.V
• Subjects: Adaptation, Physiological - physiology; Adult; Analysis; Asymmetry; Biomedical and Life Sciences; Biomedicine; Exercise Test; Feedback; Feet; Foot; Gait; Humans; Leg; Neurology; Neurosciences; Physiological aspects; Punishment; Reinforcement; Research Article; Sensorimotor integration; Sensory reinforcement; Walking; Walking - physiology; United States; Visuomotor; Reinforcement feedback; Locomotion; Adaptation; Symmetry
• ISSN: 0014-4819; 1432-1106; 1432-1106
• DOI: 10.1007/s00221-021-06275-6

Precise foot placement is dependent on changes in spatial and temporal coordination between two legs in response to a perturbation during walking. Here, we used a ‘virtual’ split-belt adaptation task to examine the effects of reinforcement (reward and punishment) feedback about foot placement on the changes in error, step length and step time asymmetry. Twenty-seven healthy adults (20 ± 2.5 years) walked on a treadmill with continuous feedback of the foot position and stepping targets projected on a screen, defined by a visuomotor gain for each leg. The paradigm consisted of a baseline period (same gain on both legs), visuomotor adaptation period (split: one high = ‘fast’, one low = ‘slow’ gain) and post-adaptation period (same gain). Participants were divided into 3 groups: control group received no score, reward group received increasing score for each target hit, and punishment group received decreasing score for each target missed. Re-adaptation was assessed 24 ± 2 h later. During early adaptation, the slow foot undershot and fast foot overshot the stepping target. Foot placement errors were gradually reduced by late adaptation, accompanied by increasing step length asymmetry (fast < slow step length) and step time asymmetry (fast > slow step time). Only the punishment group showed greater error reduction and step length re-adaptation on the next day. The results show that (1) explicit feedback of foot placement alone drives adaptation of both step length and step time asymmetry during virtual split-belt walking, and (2) specifically, step length re-adaptation driven by visuomotor errors may be enhanced by punishment feedback.