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Effects of alertness on three-dimensional eye movements
Y Suzuki1, D Straumann, V Henn
1Neurology Department, University Hospital Zürich, Zürich, Switzerland.
Japanese Journal of Ophthalmology
|October 18, 2000
Summary
Alertness impacts three-dimensional (3D) eye movements. Drowsiness increases the thickness of Listing's plane, a measure of eye movement accuracy, suggesting alertness state influences eye movement control.
Area of Science:
- Neuroscience
- Ophthalmology
- Physiology
Background:
- Three-dimensional (3D) eye movements follow specific geometric laws, such as Listing's law.
- Alertness and drowsiness states can influence motor control and neural processing.
- The rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) plays a role in eye movement control.
Purpose of the Study:
- To investigate the effects of alertness on the accuracy of three-dimensional (3D) eye movements in rhesus monkeys.
- To determine if the riMLF is essential for maintaining Listing's law during different alertness states.
Main Methods:
- Recorded 3D eye movements using dual search coils in normal rhesus monkeys.
- Compared eye movement accuracy during drowsy versus alert periods.
- Examined the effects of bilateral riMLF lesions on eye movements and alertness-related changes.
Main Results:
- Listing's law plane thickness significantly increased during drowsiness in normal monkeys.
- Asymmetric riMLF lesions exacerbated the increase in plane thickness with drowsiness.
- The increase in plane thickness during drowsiness persisted after riMLF lesions.
Conclusions:
- The integrity of the riMLF is not essential for the implementation of Listing's law.
- Drowsiness-induced inaccuracies in 3D eye movements are not solely due to saccadic burst neuron signaling.
- The velocity-to-position integrator may regulate Listing's law based on the state of alertness.