Novel method of multi-frequency flicker to stimulate SSVEP and frequency recognition

This work uses the multi-frequency flicker to stimulate SSVEP, which is different from earlier studies that using single-frequency flicker as flash stimulators. Usually, the frequency recognition of SSVEP were converted into command output with the widely used Fast fourier transform (FFT). In the experiment, seven subjects stared at the six groups of LED stimulators with two or more different and independent flicker frequencies. Three electrodes placed at Oz-A1 and Fpz (Ground) used to measure Electroencephalography (EEG) signals. After processing the EEG signal, the frequency recognition of SSVEPs were converted into command output with the FFT and the proposed novel method (NM). The results of 28-second and every 4-second segmented EEG signals were interfered by external noise that cannot to recognize the correct signals after FFT processing. On the contrary, these unrecognizable signals can clearly recognized the maximum rho value after using NM processing. In addition, the combinations of multi-frequency flicker provide the more stimulation options to apply to BCI control. This work uses only one channel of the EEG signal and the proposed novel method (NM) is simpler and have higher recognition rate than widely used FFT method.