Brain Symmetry Analysis during the Use of a BCI Based on Motor Imagery for the Control of a Lower-Limb Exoskeleton

Laura Ferrero,Mario Ortiz,José M Azorín,Eduardo Iáñez,Vicente Quiles,José A Flores

doi:10.3390/sym13091746

Abstract

Brain–Computer Interfaces (BCI) are systems that allow external devices to be controlled by means of brain activity. There are different such technologies, and electroencephalography (EEG) is an example. One of the most common EEG control methods is based on detecting changes in sensorimotor rhythms (SMRs) during motor imagery (MI). The aim of this study was to assess the laterality of cortical function when performing MI of the lower limb. Brain signals from five subjects were analyzed in two conditions, during exoskeleton-assisted gait and while static. Three different EEG electrode configurations were evaluated: covering both hemispheres, covering the non-dominant hemisphere and covering the dominant hemisphere. In addition, the evolution of performance and laterality with practice was assessed. Although sightly superior results were achieved with information from all electrodes, differences between electrode configurations were not statistically significant. Regarding the evolution during the experimental sessions, the performance of the BCI generally evolved positively the higher the experience was.

Highlights

Motor imagery (MI) is defined as the process of imagining or performing a mental execution of a movement without any actual muscle activation
The aim of this paper is to evaluate the performance of a Brain–Computer Interfaces (BCI) to control a lowerlimb exoskeleton when using information from dominant, non-dominant and both brain hemispheres
Performing MI while wearing an exoskeleton is a complex task, so it is easy for users to get distracted [16]

Summary

Introduction

Motor imagery (MI) is defined as the process of imagining or performing a mental execution of a movement without any actual muscle activation. MI, the observation of an action and the actual motor execution produce similar brain patterns [1]. There are different techniques to measure brain activity, with electroencephalography (EEG) being one of the most commonly used [2]. Sensorimotor rhythms (SMR) are brain oscillations recorded over the sensorimotor cortex. Motor processing produces changes in the ongoing SMR as event-related desynchronization (ERD) and synchronization (ERS). The phenomenon of ERD in alpha and beta band rhythms is associated with cortical areas that are ready to prepare a movement, and ERS is correlated with resting areas [3]

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