Abstract
Brain–computer interface (BCI) remains an emerging tool that seeks to improve the patient interaction with the therapeutic mechanisms and to generate neuroplasticity progressively through neuromotor abilities. Motor imagery (MI) analysis is the most used paradigm based on the motor cortex’s electrical activity to detect movement intention. It has been shown that motor imagery mental practice with movement-associated stimuli may offer an effective strategy to facilitate motor recovery in brain injury patients. In this sense, this study aims to present the BCI associated with visual and haptic stimuli to facilitate MI generation and control the T-FLEX ankle exoskeleton. To achieve this, five post-stroke patients (55–63 years) were subjected to three different strategies using T-FLEX: stationary therapy (ST) without motor imagination, motor imagination with visual stimulation (MIV), and motor imagination with visual-haptic inducement (MIVH). The quantitative characterization of both BCI stimuli strategies was made through the motor imagery accuracy rate, the electroencephalographic (EEG) analysis during the MI active periods, the statistical analysis, and a subjective patient’s perception. The preliminary results demonstrated the viability of the BCI-controlled ankle exoskeleton system with the beta rebound, in terms of patient’s performance during MI active periods and satisfaction outcomes. Accuracy differences employing haptic stimulus were detected with an average of 68% compared with the 50.7% over only visual stimulus. However, the power spectral density (PSD) did not present changes in prominent activation of the MI band but presented significant variations in terms of laterality. In this way, visual and haptic stimuli improved the subject’s MI accuracy but did not generate differential brain activity over the affected hemisphere. Hence, long-term sessions with a more extensive sample and a more robust algorithm should be carried out to evaluate the impact of the proposed system on neuronal and motor evolution after stroke.
Highlights
Stroke is one of the leading causes of physical disability seriously affecting 5 million people’s quality of life out of the 15 million who suffer from stroke around the world [1].About 80% of stroke survivors have residual mobility limitations usually associated with a foot-drop
This study presents the Brain–computer interface (BCI) integration system to the T-FLEX lower-limb exoskeleton combining two different stimulus modes for post-stroke patients
No significant differences were found in the power spectral density (PSD) mean of active periods between the stationary therapy (ST), motor imagination with visual stimulation (MIV), and motor imagination with visual-haptic inducement (MIVH) tests
Summary
Stroke is one of the leading causes of physical disability seriously affecting 5 million people’s quality of life out of the 15 million who suffer from stroke around the world [1].About 80% of stroke survivors have residual mobility limitations usually associated with a foot-drop. Post-stroke rehabilitation therapy aims to restore the patient’s physical, neurological, and psychological capacities to achieve the highest level of functional independence [5]. Robotic devices like lower-limb exoskeletons in motor rehabilitation programs have been shown to improve automatic repetitive training and promote new motor skill acquisition after stroke [6,7]. Conventional robotic control systems generally do not include efficient and natural interaction methods between users and exoskeletons [9]. In this way, the possibility of enhancing and involve the patient increasingly is a clear objective to improve the user skills in a short-term period with better results
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