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Do humans show velocity-storage in the vertical rVOR?
G Bertolini1, C J Bockisch, D Straumann
1Dipartimento di Informatica e Sistemistica, Università di Pavia, Italy. giovanni.bertolini@unipv.it
Progress in Brain Research
|August 23, 2008
Summary
The vestibular velocity-storage mechanism (VSM) contributes less to vertical rotational vestibulo-ocular reflex (rVOR) than horizontal rVOR. Vertical rVOR time constants are shorter, indicating a reduced VSM influence in this plane.
Area of Science:
- Neuroscience
- Ophthalmology
- Vestibular System Research
Background:
- The rotational vestibulo-ocular reflex (rVOR) stabilizes gaze during head rotation.
- The vestibular velocity-storage mechanism (VSM) is crucial for maintaining rVOR, particularly in the horizontal plane.
- The VSM's role in vertical rVOR is less understood.
Purpose of the Study:
- To quantify the contribution of the VSM to the vertical rVOR.
- To compare the VSM's influence on vertical versus horizontal rVOR.
- To investigate how gravity influences vertical rVOR.
Main Methods:
- Recorded eye movements in four healthy subjects during off-vertical axis rotation (OVAR).
- Utilized whole-body constant-velocity pitch rotations about an earth-horizontal axis using a 3D turntable.
- Analyzed slow-phase velocity (SPV) responses and calculated time constants.
Main Results:
- Vertical SPV responses exhibited exponentially decaying amplitudes and residual otolith-driven sinusoidal responses.
- Time constants for vertical SPV ranged from 6 to 9 seconds, significantly shorter than horizontal VSM time constants (approx. 20 s).
- Horizontal and torsional eye velocities were modulated by gravity but lacked exponential decay.
Conclusions:
- The VSM's contribution to vertical rVOR is smaller compared to horizontal rVOR.
- The VSM's velocity response appears to align with the direction of gravity.
- Vertical rVOR dynamics are primarily influenced by vestibular afferents rather than VSM storage.
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