Study on the degree of brain α wave entrainment under binocular dual-frequency stimulation

To solve the problem of frequency selection limitation in the binocular single-frequency stimulation mode，this article study the changes of phase entrainment of brain α wave in the occipital region under binocular dual-frequency simultaneous periodic stimulation for the first time. The 50Hz notch is used for the collected EEG data, the α wave data is de-noised by the band pass filter with bandwidth f_I-3 Hz~f_I+3Hz (f_I is spontaneous α wave frequency), and the trend and eye electricity are removed for all the channel data. The instantaneous phase of α wave and stimulus signal is calculated by Hilbert transform, and the degree of α wave entrainment is measured by the normalized Shannon entropy of the phase difference between the phase of α wave and stimulus signal. The results showed that under the stimulation of binocular dual-frequency, if one of the eyes is stimulated at low, medium or high frequency , and another eye is stimulated at frequency at f_I±2.4 Hz、〖2f〗_I±2.4 Hz、〖4f〗_I±2.4 Hz, the degree of phase entrainment between α wave and the frequency stimulated later eye was consistent with the change rule of the Arnold's tongue. The degree of α wave entrainment was weakened in turn in the three bands. Moreover, the degree of α wave entrainment of one eye can be changed by selecting the frequency to stimulate the other eye. The binocular dual-frequency simultaneous stimulation paradigm can provide more stimulation frequencies selection for studying the degree of brain α wave entrainment, which should be a new idea for researching more effectively on the relationship between perception and cognitive function and its potential diagnosis and treatment of cognitive impairment.