A hybrid BCI-controlled FES system for hand-wrist motor function

Motor imagery (MI) based Brain-Computer Interfaces (BCIs) controlled Functional Electrical Stimulation (FES) can help people with severe neuromuscular impairments to control their limbs by bypassing peripheral nerves and muscle pathways. However, there are still four major limitations with current MI-based BCIs for FES control: 1) They require relatively longer training and the training procedures are not clear. 2) Classification of different MI tasks within the same limb is difficult 3) MI features cannot be utilized during passive hand-motions induced by FES due to movement artifacts. 4) Few FES units are available which have real-time parameter control functionality. This study addresses these limitations by applying a hybrid BCI paradigm with a modified low-cost commercial off-the-shelf Transcutaneous Electrical Nerve Stimulation (TENS) unit. Four subjects were asked to mimic visual cues to imagine either closing or opening their dominant hand at different rates, such as fast or slow. After FES was initiated, the subjects were asked to attend to visual stimulus to elicit Steady-State Visual Evoked Potential (SSVEP) to stop FES. Results of this study showed that the modified TENS unit was able to successfully control hand motion in real-time. The classification results of different MI tasks within the same hand were promising. Furthermore, all subjects could stop the FES within 6 seconds and the average completion time was 2 seconds. The results of this study could provide insights towards future research of rehabilitation for stroke patients.