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Vestibuloocular reflex signal modulation during voluntary and passive head movements
Jefferson E Roy1, Kathleen E Cullen
1Aerospace Medical Research Unit, Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada.
Journal of Neurophysiology
|April 27, 2002
Summary
The vestibuloocular reflex (VOR) is modulated during gaze shifts. VOR pathways are suppressed during gaze redirection, suggesting efference copy of gaze commands regulates this reflex.
Area of Science:
- Neuroscience
- Ophthalmology
- Vestibular System
Background:
- The vestibuloocular reflex (VOR) stabilizes vision during head movements.
- An intact VOR is crucial for stabilizing gaze during locomotion.
- However, the VOR can interfere with voluntary gaze shifts.
Purpose of the Study:
- Investigate how VOR pathways process vestibular information during different behaviors.
- Determine the neural mechanisms underlying VOR modulation during gaze stabilization versus redirection.
- Identify inputs responsible for behaviorally dependent VOR processing.
Main Methods:
- Characterized VOR interneurons (type I and type II PVP neurons) in monkeys.
- Recorded neuronal activity during passive head rotation, active gaze shifts, and self-generated motion.
- Analyzed PVP neuron responses under conditions of gaze stabilization and gaze redirection.
Main Results:
- Type I PVP neuron responses to head motion were similar when stabilizing gaze.
- During gaze redirection, type I PVP neurons showed significantly reduced responsiveness to head velocity.
- Type II PVP neurons exhibited similar modulation patterns.
Conclusions:
- VOR pathway activity is reduced online during gaze redirection.
- Neck proprioception, neck motor commands, and self-motion knowledge do not directly influence PVP neurons.
- Efference copies of oculomotor/gaze commands are proposed to modulate VOR activity during gaze shifts.