The signal processing for extracting frequency components and phase distributions obtained from the five gaze conditions. The signal processing for extracting amplitude and phase features in (a). Oz EEG signals were bandpass-filtered within 17–23 Hz to obtain SSVEP responses by means of applying a causal Butterworth filter (6th-order, IIR Butterworth filter). The frequency components of SSVEPs at 20 Hz were extracted in every 4 cycles using Fourier method with 75% overlapped sliding Hamming window. The difference of phase distributions obtained from the four gaze conditions (0°, 90°, 180°, 270°) and one resting-state (non-gaze) condition in subject 1 (b).