Mechanical vibrotactile stimulation effect in motor imagery based brain-computer interface

Sensory stimulation played a critical role in both motivating subject's anticipation in brain-computer interface but also enhancing the sensory-motor interaction and closing the sensory motor loop. In this paper, mechanical vibrotactile stimulation effect in motor imagery was evaluated on 10 healthy subjects, and preliminary results showed that 5 subjects would achieve a reliable control above 80% with sensory stimulation as comparable with motor imagery without any stimulation. Besides, 3 subjects reached a better control with approximately 70% as compared with a chance level of 50% in motor imagery without sensory stimulation. Further analysis showed subject who was poor in conventional motor imagery condition exhibited enhanced R(2) value distribution in motor imagery with sensory stimulation condition. Meanwhile there was sensorimotor rhythmic enhancement both at upper alpha band and upper beta band in some subjects. But these rhythmic changes resulted performance reduction as incongruence of training and testing sets effect from off-line analysis. This research provided some guidance in integration of the sensory stimulation channel with motor imagery based BCI system.