Cardio-respiratory responses evoked by transient linear acceleration

Area of Science:

• Neuroscience
• Cardiorespiratory Physiology
• Vestibular System Research

Background:

• Predictive control of responses to re-orienting stimuli is crucial for spatial disorientation.
• Vestibular signals play a key role in processing motion and maintaining balance.
• Understanding cardio-respiratory responses to acceleration is vital for aviation and space travel.

Purpose of the Study:

• To evaluate how stimulus predictability influences cardio-respiratory responses to linear acceleration.
• To investigate the role of the vestibular system in mediating these responses.
• To determine if breathing phase affects the vestibulo-cardiac response.

Main Methods:

• 13 healthy subjects and 6 patients with bilateral vestibular loss underwent transient fore-aft linear acceleration (+0.26 Gx).
• Stimuli were either unpredictable (experimenter-triggered) or predictable (self-triggered), with false trials included.
• Cardio-respiratory data (ECG, respiratory frequency) and trunk acceleration were recorded.

Main Results:

• Unpredictable acceleration caused an immediate decrease in RR interval (heart rate increase) in all subjects.
• Normal subjects showed sustained or enhanced heart rate responses, while patients exhibited absent responses.
• Self-triggered acceleration also elicited prolonged but attenuated heart rate responses in healthy individuals.

Conclusions:

• A vestibulo-cardiac response is consistently evoked by transient linear acceleration, irrespective of breathing phase or predictability.
• Vestibular input is essential for generating a prolonged increase in heart rate following motion stimuli.
• The findings highlight the critical role of the vestibular system in autonomic cardiovascular regulation during motion.