Research Projects

Effects of Visual Feedback Distortion on Human Gait Speed: As an extension of the visual feedback paradigm, we have further explored the effects of visual feedback strategy and developed a different type of visual feedback distortion (so called, speed-influencing visual feedback distortion) that can influence individuals to increase their walking speed on a treadmill [3]. Increasing the intensity of gait training can be readily achieved by increasing walking speed through treadmill training. Thus, I anticipate that this proposed visual feedback method can implicitly influence individuals to change walking speed during training and produce better functional outcomes from therapy. 

[3] The effects of visual feedback distortion on gait speed (SfN 2014) 

Effects of Removing Visual Feedback on Gait Symmetry: My students and I have also investigated whether the absence of visual feedback- after it had initially been provided- had any impact on the subjects' gait patterns. During testing, a computer screen displayed the current step length of each leg to the subject by the way of two vertical bars. Halfway through each trial, only one vertical bar representing the left side continued to be displayed. This change in visual perception produced a response in every subject, causing each person to modulate his or her gait symmetry. It was shown that there was a greater immediate response when this change occurred at slower speeds, rather than at faster speeds. This result suggests that when the method of visual feedback is altered, such as in displaying step length information for only one leg rather than both legs, subjects respond by spontaneously modulating their gait pattern [4].

[4] The effects of removing visual feedback on gait symmetry: a pilot study (SfN 2015)

Effects of Ankle Perturbation during Electrical Stimulation on Gait Cadence: Effects of ankle perturbation during electrical stimulation on gait cadence We have developed and tested a novel strategy that uses an electrical stimulation technique for gait training. Entraining human gait with periodic ankle perturbations may provide a novel approach to gait training that is competent to exploit the natural oscillating dynamics of human walking. To test the feasibility of this strategy, we used a transcutaneous electrical stimulation tool to apply periodic perturbations to the ankle during treadmill walking. We aim to investigate if subjects would spontaneously change their gait periods to synchronize with the perturbation by phase-locking the electrically evoked perturbations at a terminal stance phase. The results of this study will support a new strategy for gait therapy that exploits an embedded neural oscillator interacting with peripheral mechanics and the resulting natural dynamics of walking, which are essential elements of gait training [5].

[5] The effects of ankle perturbation during FES on gait cadence: a pilot study (BMES 2017)

Effects of Feedback Distortion on Visuomotor Adaptation with Gait: Visuomotor (sensorimotor) adaptation refers to the phenomenon where visually guided motor behavior changes in response to a sensory-prediction error signal (difference between the aiming and feedback location), and also plays an important role in motor planning and execution. Studies on visuomotor adaptation generally consist of arm-reaching tasks, but less is known about how it effects human locomotion. We have proposed a novel task design, called visual feedback distortion, in which the left and right step lengths are measured during treadmill walking and displayed to subjects as two vertical bars, and the length of only one bar is distorted. We further investigated how gait adaptation, driven by a sensory-prediction error, may be compromised in two different modalities of feedback distortion (visual (shape) feedback & digit feedback) questioning what constitutes the sensory feedback that results in forward model adaptation? 

Sensory-prediction errors constitute the difference between the actual sensory feedback and the expected sensory feedback for a given motor command. We demonstrate that sensorimotor adaptation still arises even when the actual sensory feedbacks are represented in an abstract or informative way (visual shape or digit forms in our study) suggesting that visuomotor adaptation in gait does not necessarily rely on visually presented feedback and is not restricted to any one form.

[6] The effects of Feedback Distortion on Visuomotor Adaptation with Gait (SfN 2018)

A locomotor adaptation using visual feedback distortion: will does an individual’s cognitive belief regarding the adequacy of visual feedback affect visuomotor adaptation?: We hoped to discover an effective method for increasing retention of motor learning by comparing the gait retention rate of subjects who experience visual feedback (VF) of gait symmetry while walking on a treadmill in two different conditions. In a naive condition, subjects walking on distorted VF were unaware that an asymmetrical gait was being induced and that the VF was distorted, while in an informed condition, subjects were aware that an asymmetrical gait was being induced and that the VF was distorted. Our study aims to examine whether an individual’s belief in the accuracy of VF will influence the efficiency of locomotor adaptation on spatial gait symmetry. The clinical applications of this experiment would be the development of more effective gait rehabilitation programs and techniques for victims of stroke and other related neurological disorders.

[7] A Locomotor Adaptation Using Visual Feedback Distortion: Role of Explicit and Implicit Action (BMES 2020)

Concurrent locomotor adaptation and retention to visual and split-belt perturbation: 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) & split-belt treadmill (SBT) walking. In SBT walking, spatiotemporal gait adaptation can be readily made, but it quickly fades. Gait adaptation to implicit VFD tends to persist longer, potentially due to more implicit motor learning processes involvement. Thus, I investigated whether the combined strategies lead to more effective changes in symmetric gait patterns with longer retention. I compared retention of preserved asymmetric pattern acquired by implicit VFD+SBT walking with SBT walking alone and SBT walking with conscious correction. The results of this study showed a greater retention rate during the implicit VFD+SBT trial than the SBT walking only or the SBT walking with conscious correction trials [8]. The implicit visual distortion paradigm can then 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.

[8] Dual locomotor adaptation and retention to visual and split-belt perturbation (SfN 2021)