Visual Attention and Motion Visibility Modulate Motor Resonance during Observation of Human Walking in Different Manners.

Tomotaka Ito,Yuta Ishimaru,Daisuke Kimura,Tomonori Kihara,Masanori Kamiue,Akio Tsubahara

doi:10.3390/brainsci11060679

Abstract

To advance our knowledge on the motor system during cyclic gait observation, we aimed to explore the effects of gaze fixation on corticospinal excitability evaluated by single-pulse transcranial magnetic stimulation (TMS). Fourteen healthy adult volunteers watched a video of a demonstrator walking on a treadmill under three different conditions: (1) observing the right lower limb, (2) observing the right ankle joint, and (3) observing the right lower limb on a video focused on the area below the knee. In each condition, motor-evoked potentials elicited by TMS in the tibialis anterior (TA) muscle were measured synchronously with the demonstrator’s initial contact and toe-off points. Directing visual attention to the ankle joint and focusing on its movements caused corticospinal facilitation in the TA muscle compared with watching the video without any visual fixation. In addition, phase-dependent differences in corticospinal excitability between the initial contact and toe-off points were only detected when the visibility range was restricted to below the knee. Our findings indicated that motor resonance during cyclic gait observation is modulated by visual attention and motion visibility in different activation manners.

Highlights

Over the past several decades, a large number of studies using brain imaging and neurophysiological techniques, such as transcranial magnetic stimulation (TMS), have clarified the brain regions [1,2] and properties of the motor system [3] during the observation of actions conducted by others
The Wilcoxon signed-rank test showed no significant differences between the two Motor-evoked potentials (MEPs) values measured while observing the same picture of the treadmill before and after the gait observation (p = 0.594)
This result showed that the excitability in the corticospinal tract was not affected by the short-term gait observation itself and was constant throughout the entire experiment

Summary

Introduction

Over the past several decades, a large number of studies using brain imaging and neurophysiological techniques, such as transcranial magnetic stimulation (TMS), have clarified the brain regions [1,2] and properties of the motor system [3] during the observation of actions conducted by others. Action observation is used as an alternative or adjunct to the physical rehabilitation approach and is clinically shown to promote motor (re)learning for the recovery of motor functions [4,5,6,7,8,9]. As several recent meta-analyses have reported that action observation therapy (AOT) is effective in restoring upper limb function [6,7,8] and walking ability [7,9] in patients with stroke, AOT appears to be a beneficial rehabilitation approach for those with upper or lower limb disorders. To our knowledge, only one study has assessed walking as an experimental task and directly reported the observation/execution matching of brain regions concerning walking using functional magnetic resonance imaging methods [11]

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