Otoliths - Accelerometer and seismometer; Implications in Vestibular Evoked Myogenic Potential (VEMP)

Area of Science:

• Vestibular physiology
• Biomechanics
• Auditory and vestibular system

Background:

• Vestibular otolithic organs transduce head acceleration, with functionality extending to 2-3 kHz.
• Their response mode shifts from accelerometer to seismometer above their natural frequency.

Purpose of the Study:

• To develop a mechanics model predicting otolithic organ transduction.
• To investigate the response mechanism for vestibular evoked myogenic potentials (VEMPs) at higher frequencies.

Main Methods:

• A mechanics model was developed to predict otolithic organ response.
• The model was converted to a transfer function using hair cell bundle deflection.
• Measured threshold stimuli and deflections were compared to model predictions.

Main Results:

• The model accurately predicts otolithic organ response below and above their undamped natural frequency.
• Adjusted threshold deflection values fell within measured ranges.
• Otolithic organs utilize a seismometer mode for VEMP transduction at 500-1000 Hz.

Conclusions:

• The developed model provides insight into otolithic organ transduction mechanics.
• Otoliths act as seismometers for VEMP generation at clinically relevant frequencies.
• This explains the mechanism of VEMP response to stimuli above the otoliths' natural frequency.