Towards Effective Non-Invasive Brain-Computer Interfaces Dedicated to Gait Rehabilitation Systems

Abstract

In the last few years, significant progress has been made in the field of walk rehabilitation. Motor cortex signals in bipedal monkeys have been interpreted to predict walk kinematics. Epidural electrical stimulation in rats and in one young paraplegic has been realized to partially restore motor control after spinal cord injury. However, these experimental trials are far from being applicable to all patients suffering from motor impairments. Therefore, it is thought that more simple rehabilitation systems are desirable in the meanwhile. The goal of this review is to describe and summarize the progress made in the development of non-invasive brain-computer interfaces dedicated to motor rehabilitation systems. In the first part, the main principles of human locomotion control are presented. The paper then focuses on the mechanisms of supra-spinal centers active during gait, including results from electroencephalography, functional brain imaging technologies [near-infrared spectroscopy (NIRS), functional magnetic resonance imaging (fMRI), positron-emission tomography (PET), single-photon emission-computed tomography (SPECT)] and invasive studies. The first brain-computer interface (BCI) applications to gait rehabilitation are then presented, with a discussion about the different strategies developed in the field. The challenges to raise for future systems are identified and discussed. Finally, we present some proposals to address these challenges, in order to contribute to the improvement of BCI for gait rehabilitation.

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

“…On the supraspinal level, cortical activation patterns have been monitored by means of electroencephalography (EEG) during lower limb movements [ 21 , 22 ], actual walking on a treadmill (TW) [ 23 – 29 ] and robot-assisted treadmill walking (RATW) [ 30 – 35 ], see [ 36 , 37 ] for a review. Most of these studies monitored event-related spectral perturbations (ERSPs) which reflect averaged dynamic changes in amplitude of the broad band EEG frequency spectrum as a function of time relative to a specific event, in the case of TW and RATW, the phases of the gait cycle [ 38 ].…”

“…Most of these studies monitored event-related spectral perturbations (ERSPs) which reflect averaged dynamic changes in amplitude of the broad band EEG frequency spectrum as a function of time relative to a specific event, in the case of TW and RATW, the phases of the gait cycle [ 38 ]. The few studies which considered ERSPs during TW and RATW have mainly revealed power modulations in the alpha/mu (8–12 Hz), beta (12–30Hz) and low gamma (30–45 Hz) bands over the sensorimotor cortex related to the phases of the gait cycle, see [ 37 ] for a review and Table 1 for an overview. As compared to the studies presented in Table 1 , where active RATW is mostly compared to passive RATW (i.e., with the same device settings) or standing, the purpose of this study was to look at possible effects of different amounts of guidance force of a robotic gait training orthosis (i.e., Lokomat) on brain activity and compare it to unassisted TW.…”

Temporal and spatial organization of gait-related electrocortical potentials

“…An important advantage of EEG is its usability in dynamic situations and its high temporal resolution enabling researchers to link brain potentials to the timing of lower limb movements [3]. One of the earliest and very consistent findings with regard to EEG and voluntary movement is the so-called movement-related cortical potential (MRCP), see [31] for a review.…”

“…Yet until now no study explored the spatial and temporal characteristics of an MRCP during actual walking. Only two studies have measured EEG during real walking, but mainly looked at characteristics of the frequency spectra [11,30], see [3] for a review. Therefore, the purpose of this study was to investigate (1) whether an averaged electrocortical potential could be identified during walking, (2) whether this potential was in temporal relation to the gait cycle and (3) which sources were underlying this potential.…”

Flexor Dysfunction Following Unilateral Transient Ischemic Brain Injury Is Associated with Impaired Locomotor Rhythmicity

“…These studies, however, do not focus on integrating various parameters of muscle function into a holistic predictive model of output. Other studies aim at modeling gait deficits for the purpose of development of prostheses that aid functional recovery noninvasively224 , which is the desired direction towards rehabilitative cost reduction225 . This raises several issues that need to be addressed when investigating the mathematical correlates of motor function.…”