Human-Robot Interaction: Does Robotic Guidance Force Affect Gait-Related Brain Dynamics during Robot-Assisted Treadmill Walking?

Kristel Knaepen,Marc Michielsen,Romain Meeusen,Eric Kerckhofs,Andreas Mierau,Eva Swinnen,Dirk Lefeber,Helio Fernandez Tellez

doi:10.1371/journal.pone.0140626

Abstract

In order to determine optimal training parameters for robot-assisted treadmill walking, it is essential to understand how a robotic device interacts with its wearer, and thus, how parameter settings of the device affect locomotor control. The aim of this study was to assess the effect of different levels of guidance force during robot-assisted treadmill walking on cortical activity. Eighteen healthy subjects walked at 2 km.h-1 on a treadmill with and without assistance of the Lokomat robotic gait orthosis. Event-related spectral perturbations and changes in power spectral density were investigated during unassisted treadmill walking as well as during robot-assisted treadmill walking at 30%, 60% and 100% guidance force (with 0% body weight support). Clustering of independent components revealed three clusters of activity in the sensorimotor cortex during treadmill walking and robot-assisted treadmill walking in healthy subjects. These clusters demonstrated gait-related spectral modulations in the mu, beta and low gamma bands over the sensorimotor cortex related to specific phases of the gait cycle. Moreover, mu and beta rhythms were suppressed in the right primary sensory cortex during treadmill walking compared to robot-assisted treadmill walking with 100% guidance force, indicating significantly larger involvement of the sensorimotor area during treadmill walking compared to robot-assisted treadmill walking. Only marginal differences in the spectral power of the mu, beta and low gamma bands could be identified between robot-assisted treadmill walking with different levels of guidance force. From these results it can be concluded that a high level of guidance force (i.e., 100% guidance force) and thus a less active participation during locomotion should be avoided during robot-assisted treadmill walking. This will optimize the involvement of the sensorimotor cortex which is known to be crucial for motor learning.

Highlights

Robot-assisted gait training has a large potential to augment motor function and facilitate walking recovery in persons with neurological gait disorders [1,2,3,4,5]
This study demonstrated gait-related spectral modulations in the mu, beta and low gamma bands over the sensorimotor cortex related to specific phases of the gait cycle
Marginal differences in the spectral power of the mu, beta and low gamma bands could be identified between robot-assisted treadmill walking (RATW) with different levels of guidance force (GF)

Summary

Introduction

Robot-assisted gait training has a large potential to augment motor function and facilitate walking recovery in persons with neurological gait disorders [1,2,3,4,5]. It has some important advantages over manually assisted gait training such as the possibility to 1) increase the intensity and standardization of the training program, 2) offer a more complex multisensory stimulation of the human motor control system and 3) give extensive extrinsic feedback to the patient [6]. Bearing in mind that gait rehabilitation devices are primarily used to restore lost motor functions, assessing effects of HRI on the central level (i.e., central nervous system (CNS)) is important, as basic motor patterns are generated on the spinal as well as the supraspinal level [18, 19] and motor intentions and high-level adaptations of motor patterns originate at the supraspinal level [10, 20]

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Conclusion