High and Low Pitch Sound Stimuli Effects on HRV-EEG Coupling

Abstract Purpose : This study aimed to explore the influence of sound stimulation on the autonomic nervous system and the potential coupling between cardiac and cerebral activities. Methods : Thirty-one participants underwent exposure to periods of silence and two distinct continuous, non-repetitive pure tone stimuli: low pitch (110 Hz) and high pitch (880 Hz). Electroencephalography (EEG) data from electrodes F3, F4, F7, F8, Fp1, Fp2, T3, T4, T5, and T6, along with R-R interval data for heart rate, were recorded. Heart-brain connectivity was assessed using wavelet coherence between heart rate variability (HRV) and EEG envelopes (EEGE). Results : We observed that heart rates were notably higher during silence compared to both high and low-pitch sound periods. The high-frequency (HF) band of HRV was significantly elevated across all tested conditions. However, an interaction between HRV bands and conditions emerged when examining normalized power. The low-pitch stimulus resulted in markedly reduced normalized power in the HF band compared to silence. Notably, HRV-EEGE coherence was considerably enhanced during silence and low-pitch sound intervals compared to high-pitch intervals, especially between the beta band and the low-frequency HRV range. This implies a differential involvement of the frontal and temporal brain regions, in response to varying auditory stimuli. Conclusion : Our findings highlight the essential nature of discerning the complex interrelations between sound frequencies and their implications for heart-brain connectivity. Such insights could have ramifications for conditions like seizures and sleep disturbances. A deeper exploration is warranted to decipher the potential advantages or drawbacks of specific sound stimuli in diverse clinical scenarios.