Abstract

Background. Motor imagery engages much of the same neural circuits as an overt movement. Therefore, the mental rehearsal of movements is often used to supplement physical training and might aid motor neurorehabilitation after stroke. One attempt to capture the brain’s involvement in imagery involves the use, as a marker, of the depression or event-related desynchronization (ERD) of thalamocortical sensorimotor rhythms found in a human electroencephalogram (EEG). Using fast real-time processing, it is possible to make the subject aware of their own brain reactions or—even better—to turn them into actions through a technology called the brain–computer interface (BCI). However, it remains unclear whether BCI-enabled imagery facilitates a stronger or qualitatively different brain response compared to the open-loop training. Methods. Seven healthy volunteers who were experienced in both closed and open-loop motor imagery took part in six experimental sessions over a period of 4.5 months, in which they performed kinesthetic imagery of a previously known set of finger and arm movements with simultaneous 30-channel EEG acquisition. The first and the last session mostly consisted of feedback trials in which the subjects were presented with the classification results of the EEG patterns in real time; during the other sessions, no feedback was provided. Spatiotemporal and amplitude features of the ERD patterns concomitant with imagery were compared across experimental days and between feedback conditions using linear mixed-effects modeling. Results. The main spatial sources of ERD appeared to be highly stable across the six experimental days, remaining nearly identical in five of seven subjects (Pearson’s ρ > 0.94). Only in one subject did the spatial pattern of activation statistically significantly differ (p = 0.009) between the feedback and no-feedback conditions. Real-time visual feedback delivered through the BCI did not significantly increase the ERD strength. Conclusion. The results imply that the potential benefits of MI could be yielded by well-habituated subjects with a simplified open-loop setup, e.g., through at-home self-practice.

Highlights

  • Such motor imagery brain–computer interface (BCI) use a well-known and prominent neural marker of sensorimotor activation, known as the event-related desynchronization of sensorimotor rhythms (ERD of SMR), which is found in a human electroencephalogram (EEG) and represented as a reduction in the amplitude of oscillatory activity, most commonly in the mu (8–14 Hz) and beta

  • FR condition organized in pairs for experimental day and subject

  • The goal of the current study was to determine if the mental practice efficiency in experienced users could be enhanced by using a sensorimotor rhythm-based brain

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Summary

Introduction

One strategy that is adopted for validating and enhancing mental practice is the use of real-time feedback enabled by a brain–computer interface (BCI)—a technology that uses real-time neural activity for the detection (statistical classification) of associated mental states [6] Such motor imagery BCIs use a well-known and prominent neural marker of sensorimotor activation, known as the event-related desynchronization of sensorimotor rhythms (ERD of SMR), which is found in a human electroencephalogram (EEG) and represented as a reduction in the amplitude of oscillatory activity, most commonly in the mu (8–14 Hz) and (or) beta (15–30 Hz) frequency bands. Using fast real-time processing, it is possible to make the subject aware of their own brain reactions or—even better—to turn them into actions through a technology called the brain–computer interface (BCI) It remains unclear whether BCI-enabled imagery facilitates a stronger or qualitatively different brain response compared to the open-loop training. The results imply that the potential benefits of MI could be yielded by well-habituated subjects with a simplified open-loop setup, e.g., through at-home self-practice

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