Target Frequency Band of Cognition and Tempo of Music: Cardiac Synchronous EEG

It is over 150 years ago that the intimate interaction between the heart and the brain was realized by Claude Bernard, and of all the organs in the human body, the heart is among the ones that have the most extensive neural connection with the brain. In this study, we used cardiac-synchronized EEG segments to investigate the effects of tempo and cognition induced by auditory stimuli. To evaluate the effects of tempo, two songs, of slow and fast tempo were used, and to evaluate the effects of cognition, the subjects' favorite song was used (known song). The selected slow and the fast tempo songs were unknown to all subjects. To further investigate the effects of cognition, the phase of local spectra of the known and unknown fast tempo songs were randomized to alter the amount of cognition of songs. ECG and EEG were recorded from 14 subjects when they were listening to music and during silence (control). The 300-millisecond EEG segments ending at R-peaks of ECG were extracted. The frequency bands of Delta, Theta, Alpha, Beta, Gama and Gamma2 within EEGs were also analyzed to determine which bands were more sensitive to the induced changes. The eigenvalue analysis of covariance matrix of synchronized EEG showed that Alpha band in EEG from parietal zone was the most sensitive band among all other frequency bands to auditory stimuli. The cognition of song had much higher impact on Gamma and Gamma2 bands of EEGs from right hemisphere, which corresponds to music awareness, than tempo of song even though tempo is considered as the most impactful acoustic structural feature of music on physiological variables. The higher impact of local phase randomized version of known song than local phase randomized of unknown song on these bands also verifies the stronger impact of cognition relative to tempo.