A NIRS-based brain-computer interface system during motor imagery: system development and online feedback training.

A brain-computer interface (BCI) to detect motor imagery from cerebrum hemodynamic data measured by NIRS (near-infrared spectroscopy) was constructed and the effect of the online feedback training for subjects was evaluated. Concentrations of Oxy- and deOxy-hemoglobin in the motor cortex during motor imagery of subject's right hand was measured by 52-channel NIRS system, and the mean magnitude of measured signal near C3 in the International 10-20 System was visually fed back online to the subject. On two out of three subjects, it was shown that the ratio between the averaged value and the standard deviation over trials (S/N ratio) of Oxy-hemoglobin signal elicited by the imagery of subject's right hand was increased by the 5-day online feedback training. Detailed investigation of the effect of the online feedback training on brain activities was left for further study.