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Visually induced plasticity of postsaccadic ocular drift in normal humans.
Z Kapoula1, L M Optican, D A Robinson
1Laboratory of Sensorimotor Research, National Institutes of Health, Bethesda, Maryland 20892.
Journal of Neurophysiology
|May 1, 1989
Summary
Human subjects adapted to a moving visual pattern, developing a postsaccadic ocular drift. This drift, consistent with Hering's law, suggests changes in saccadic eye movement innervation.
Area of Science:
- Neuroscience
- Ophthalmology
- Vision Science
Background:
- Human saccadic eye movements are complex motor commands.
- Postsaccadic eye drift is a normal phenomenon, particularly in adducting eyes.
Purpose of the Study:
- To investigate adaptive changes in human postsaccadic eye movements.
- To determine if prolonged exposure to a moving visual pattern induces ocular drift.
- To characterize the properties of this induced drift.
Main Methods:
- Five human subjects underwent training with a computer-controlled, full-field random-dot pattern.
- The pattern moved horizontally, synchronized with saccades (eye movements).
- Eye movements were recorded using electrooculography and eye-coil/magnetic-field methods before and after adaptation.
Main Results:
- Subjects developed a zero-latency, postsaccadic ocular drift in the dark, matching the pattern's motion direction.
- Drift amplitude was approximately 6% of saccade size, with a time constant of 108 ms.
- Adaptation preserved the normal adduction-adduction asymmetry in saccadic drift, conforming to Hering's law.
Conclusions:
- Prolonged visual-motor adaptation can induce significant postsaccadic ocular drift.
- The induced drift is conjugate and consistent with modifications in saccadic innervation parameters.
- Findings in humans align with previous studies in non-human primates.