Cross-Modal Effect of Presenting Visual and Force Feedback That Create the Illusion of Stair-Climbing

Takumi Okumura,Yuichi Kurita

doi:10.3390/app11072987

Abstract

Image therapy, which creates illusions with a mirror and a head mount display, assists movement relearning in stroke patients. Mirror therapy presents the movement of the unaffected limb in a mirror, creating the illusion of movement of the affected limb. As the visual information of images cannot create a fully immersive experience, we propose a cross-modal strategy that supplements the image with sensual information. By interacting with the stimuli received from multiple sensory organs, the brain complements missing senses, and the patient experiences a different sense of motion. Our system generates the sense of stair-climbing in a subject walking on a level floor. The force sensation is presented by a pneumatic gel muscle (PGM). Based on motion analysis in a human lower-limb model and the characteristics of the force exerted by the PGM, we set the appropriate air pressure of the PGM. The effectiveness of the proposed system was evaluated by surface electromyography and a questionnaire. The experimental results showed that by synchronizing the force sensation with visual information, we could match the motor and perceived sensations at the muscle-activity level, enhancing the sense of stair-climbing. The experimental results showed that the visual condition significantly improved the illusion intensity during stair-climbing.

Highlights

When the motion-related region of the brain is damaged by a stroke, the body cannot execute its desired movements
We determined whether the force feedback in the pneumatic gel muscle (PGM) suit creates the desired muscle activity
We have proposed a method that generates motion illusions by presenting a force sensation through artificial muscles that promote muscle activity

Summary

Introduction

When the motion-related region of the brain is damaged by a stroke, the body cannot execute its desired movements. In many stroke-paralyzed patients, the neural network controlling the paralyzed limb shrinks because the limb is not used, causing further functional depression. This scenario constitutes a vicious circle [1,2]. A visually induced kinesthetic illusion instills the sense of body movement when the body is moving neither voluntarily nor passively. Such an illusion increases the excitability of corticospinal tracts during voluntary movement and activity in the premotor and supplementary motor areas of the brain [5]. Illusion-based rehabilitation is applied to dynamic motions such as walking [7]

Methods

Results

Discussion

Conclusion