Phase synchrony measurement in motor cortex for classifying single-trial EEG during motor imagery

A motor imagery based brain-computer interface (BCI) translates the subject's motor intention into a control signal. For this BCI system, most algorithms are based on power changes of mu and beta rhythms. In this paper, we employ the measurement of phase synchrony to investigate the activities of the supplementary motor area (SMA) and primary motor area (M1) during left/right hand movement imagery. The single-trial phase locking value (PLV) features were derived from intrinsic large-scale and local-scale phase synchronies between and within SMA and M1. The classification performance suggests that phase synchrony is an additional robust feature for differentiating motor imagery states.