Phase-Locked and Non-Phase-Locked Event-Related Oscillations and Channel Power Spectra Analysis during Motor Imagery with Speed Parameters for BCRI

Phase-locked and non-phase-locked event-related oscillations and channel spectra during motor imagery with speed parameters (fast 4Hz and slow 1Hz) were investigated in the paper. EEG signals related to imagination of six tasks that involved three limbs (left and right index fingers and right toes) and two speeds were first separated from original EEG signals mixed with noises by ICA. Then, event-related EEG trials were superposed and averaged to get time domain average EEG that was decomposed by wavelet transform to investigate phase locked event-related oscillations. Event-related EEG trials were also decomposed by wavelet transform respectively and then superposed and averaged to investigate non-phase-locked event related oscillations. In addition, power spectra for selected channel were calculated by FFT. By these methods, the latency of 50~536ms and the low frequency band of 2.7~8Hz for an increase in power early after the event, latencies and frequency bands for significant different changes and a different degree decrease in power at high frequency band between fast and slow motor imagery, and ERD / ERS in a broad frequency band for selected channels were found. Simultaneously extracting phase-locked and non-phase-locked event-related oscillations in broadband range may be very important for acquiring complete information about event-related EEG during motor imagery with speed parameters. The research results may be used in feature extraction for brain-controlled robots interface (BCRI). In the based on brain cognitive robots control, this study is also expected to provide some degree continuous and fine control strategies for BCR.