Schematic diagram of the virtual reality (VR)-based brain-computer interface for avatar control. (A) Three pairs of bipolar EEG recordings. The electrode placements were at Cz, C4, C3, and 25 mm anterior of these positions. (B) Feature extraction. Band power (BP) in the subject-specific frequency bands (mu rhythm: 8-13 Hz; beta rhythm: 25-35 Hz) was extracted from the ongoing EEG signals. (C) Visual feedback. The BP feature of the beta rhythm (25-35 Hz) at Cz and the output of the LDA classifier for hand MI classification are displayed in the left-hand screen as vertical and horizontal feedback bars, respectively. The internet-based VR application is displayed in the right-hand screen. (D) Command translation. The user's motor intention was translated into the avatar's action.