Movement Anticipation and EEG: Implications for BCI-Contingent Robot Therapy
- Author(s): Norman, Sumner Lee
- Advisor(s): Reinkensmeyer, David J
- et al.
Brain-computer interfacing is a technology that could potentially be used to improve patient effort in robot-assisted rehabilitation therapy. For example, movement intention reduces mu (8-13 Hz) oscillation amplitude over the sensorimotor cortex, a phenomenon referred to as event-related desynchronization (ERD). In an ERD-contingent assistance paradigm, initial BCI-enhanced robotic therapy studies have used ERD as a trigger signal for providing robotic assistance to limb movement. Here we investigated how ERD changed as a function of audio-visual stimuli, overt movement from the participant, and robotic assistance. Eight unimpaired subjects played a musical computer game designed for rehabilitation therapy using the FINGER robotic exoskeleton. In the game, the participant and robot matched finger movement timing to audiovisual stimuli in the form of notes approaching a target on the screen set to the consistent beat of popular music. The audiovisual stimulation of the game alone did not cause ERD, before or after training. In contrast, overt movement by the subject caused ERD, whether or not the robot assisted the finger movement. Notably, ERD was also present when the subjects remained passive and the robot imposed movement. This ERD occurred in anticipation of the passive finger movement with similar onset timing as for the overt movement conditions. These results demonstrate that ERD can be contingent on expectation of robotic assistance; that is, the brain generates an anticipatory ERD in expectation of a robot-imposed but predictable movement. This is a caveat that should be considered in designing BCI interfaces for enhancing patient effort in robotically-assisted therapy.