Concurrent locomotor adaptation and retention to visual and split-belt perturbations

Gait asymmetry is a common symptom in groups with neurological disorders and significantly reduces gait efficiency. To develop efficient training for gait rehabilitation, we propose a novel gait rehabilitation paradigm that combines two distinct perturbation strategies: visual feedback distortion (VFD) and split-belt treadmill (SBT) walking. In SBT walking, spatiotemporal gait adaptation can be readily achieved, but it quickly fades after training. Gait adaptation to implicit VFD in an unconscious manner tends to persist longer, potentially due to a greater engagement of implicit learning during training. Thus, we investigated whether the combined strategies would lead to more effective changes in symmetric gait patterns with longer retention periods. We compared the retention of the preserved asymmetric pattern acquired by "implicit VFD+SBT walking" with "SBT-only walking" and with "SBT walking with conscious correction". In the implicit VFD+SBT walking, the speed of the two belts was gradually changed, the visual representation of gait symmetry was implicitly distorted, and no instructions were given to subjects except to watch the visual feedback. In the SBT walking with conscious correction, subjects were instructed to consciously correct their steps with the help of visual feedback while SBT walking. The SBT-only walking consisted of SBT walking with no visual feedback. After the 7-minute adaptation period, we removed the visual feedback and the split-belt perturbations, and we assessed the retention of the preserved asymmetric pattern while subjects continued walking for the 15-minute post-adaptation period. In a group of subjects who spontaneously showed visuomotor adaptation in response to the implicit VFD (16 out of 27 subjects), we found a greater retention rate during the implicit VFD+SBT walking trial than the SBT-only walking or the SBT walking with conscious correction trials. The implicit visual distortion paradigm delivered in an attention-independent (unconscious) manner can be utilized and integrated into SBT walking to improve the efficacy of symmetric gait adaptation by producing longer-lasting effects on the retention of a newly learned motor pattern.