Directed transfer function (DTF) is good at characterizing the pairwise interactions from whole brain network and has been applied in discrimination of motor imagery (MI) tasks. Considering the fact that MI electroencephalogram signals are more non-stationary in frequency domain than in time domain, and the activated intensities of α band (8–13 Hz) and β band [13–30 Hz, with $$\beta_{1}$$ β 1 (13–21 Hz) and $$\beta_{2}$$ β 2 (21–30 Hz) included] have considerable differences for d...
