Interaural translational VOR: suppression, enhancement, and cognitive control.

Area of Science:

• Neuroscience
• Vestibular System
• Human Physiology

Background:

• The vestibuloocular reflex (VOR) stabilizes gaze during head movements.
• The translational VOR (tVOR) specifically compensates for linear head motion.
• The influence of cognitive factors on the early tVOR response is not fully understood.

Purpose of the Study:

• To investigate how cognitive factors, specifically prior knowledge of head motion direction and target location, affect the early translational vestibuloocular reflex (tVOR).
• To determine the timing and extent of cognitive influence on tVOR gain and corrective saccades.

Main Methods:

• Six healthy subjects underwent head translations while viewing head-fixed or space-fixed targets in darkness.
• Testing paradigms included varying levels of predictability regarding target location and head motion direction.
• Slow-phase tVOR gain was calculated relative to ideal performance, and saccade timing was analyzed.

Main Results:

• When target location and head motion were known, tVOR slow-phase gain was significantly higher compared to when only one was known or when both were unpredictable.
• Cognitive factors influenced the timing of corrective saccades, with visual error signals more critical for head-fixed targets and preprogramming for space-fixed targets.
• Simulations indicated that cognitive modulation of tVOR could occur at the level of otolith afferent synapses in the vestibular nuclei.

Conclusions:

• The translational VOR, including its slow-phase response and corrective saccades, is significantly modulated by cognitive factors.
• Knowledge of head motion direction and target location influences tVOR performance as early as 20 ms after motion onset.
• These findings suggest that higher-level cognitive control can influence the VOR at very early stages of sensory processing.