# Hemodynamic Response to Air-Conducted Sound Stimulus Is Mediated via Vestibulosympathetic Reflex

## TL;DR

The study shows that air-conducted sound affects heart rate through a reflex involving the vestibular system and autonomic nervous system.

## Contribution

The novel finding is that air-conducted sound stimulates the vestibulosympathetic reflex in healthy individuals but not in those with vestibular neuritis.

## Key findings

- Otolithic stimulation with ACSS reduced heart rate during passive tilt in healthy participants.
- No significant heart rate changes were observed in participants with vestibular neuritis during ACSS.
- Respiratory sinus arrhythmia decreased with ACSS in healthy individuals.

## Abstract

Aim: To investigate the vestibulosympathetic reflex (VSR) in humans by comparing the hemodynamic responses to air-conducted sound stimulus (ACSS) of the vestibular system between healthy individuals and participants with vestibular neuritis (VN). Methods: Twenty-one healthy controls and seven participants with VN were enrolled. Each autonomic test was first conducted without and then with ACSS of the vestibular system. The following autonomic tests were performed: heart rate response to Valsalva maneuver; heart rate response to deep breathing; and heart rate and blood pressure response to a supine position, passive tilt, and active standing. Results: In healthy participants, there was a difference between respiratory sinus arrhythmia values without and with otolithic stimulation (26.63 ± 6.16 vs. 24.67 ± 7.34, p = 0.02). During passive tilt, the average heart rate throughout ACSS was lower than immediately before ACSS (88.63 ± 14.68 vs. 90.96 ± 14.93, p = 0.001). In participants with VN, no such differences were observed. Conclusions: This study demonstrated a significant effect of otolithic stimulation with ACSS on heart rate during passive tilt in healthy participants. These findings suggest that ACSS of the vestibular system could be a valuable method for future research on the VSR.