2008 Volume 10 Issue 2 Pages 215-224
Noninvasive electroencephalogram (EEG)-based brain-computer interface (BCI)provides a new communication channel to replace an impaired motor function of patients. EEG recordings during right and left motor hand imageries are expected to be available to move a cursor to a target on a computer screen or to move a wheelchair. In this paper, similarities and differencies of EEGs among right/left hand movement sand right/left hand movement imageries have been studied to verify the usefulness of the EEG-based BCI during motor imageries. In the experiments, visual cues ("right hand" or "left hand") were presented for 3 s with the interval time of 4.5-5.5 s. The subjects were asked to move one of their hands or imagine it when visual cues were appeared. EEG signals were recorded from 63 Ag/AgCl scalp electrodes. First, blinking artifacts are eliminated by using ICA. Second, the wavelet transform was applied to obtain the time-varying energy of EEG signals during right/left movement or their imagery. Secondly, the power spectra were normalized. Lastly, topographes were analyzed from them. The event-related synchronizations (ERS)of the beta rhythms were observed after movements or their imageries in the vicinity of the motor area, and demonstrating beta rhythm is a promissing indicator for BCI.
