Enhanced Motor Imagery of Lower Limbs Induced by Gait Phase Encoding Sensory Electrical Stimulation

Abstract

Motor imagery-based brain-computer interfaces (MI-BCI) help patients to reconstruct damaged neural path-ways in the field of neurorehabilitation. However, difficulties in performing abstract imagery tasks and generating discriminable EEG signals for some subjects limit the application of MI-BCI, and the devices required for the visual guidance paradigm are not portable in MI-BCI application scenarios for wearable robotic systems. In this study, we propose an enhanced motor imagery paradigm combining sequential elec-trical stimulation (SES) encoded by gait phase with a gait motor imagery (MI) task, guiding subjects to perform MI task with task-mapped electrical stimulation (ES). The goal of the novel paradigm is to reduce the difficulty of lower limbs MI task and to improve the performance of the MI-BCI by combining movement and sensation. We conducted comparison experiments on eight healthy subjects, and the MI task in the SES-Stim paradigm achieved greater activation of motor cortex in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\alpha$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\beta$</tex> rhythm, and the proposed SES-Stim paradigm could improve the classification performance.