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Evidence for nonretinal feedback in combined version-vergence eye movements
K P Krommenhoek1, J A Van Gisbergen
1Department of Medical Physics and Biophysics, KUN, Nijmegen, The Netherlands.
Experimental Brain Research
|January 1, 1994
Summary
This study shows that eye movement systems use non-visual cues to guide rapid eye movements in direction and depth. The saccadic system accurately uses this information, while the vergence system shows reduced accuracy.
Area of Science:
- Neuroscience
- Ophthalmology
- Motor Control
Background:
- A quantitative model for rapid eye movements in direction and depth proposes shared initiation and local feedback loops using efference copy signals.
- Extraretinal signals are hypothesized to guide both saccadic and vergence systems.
Purpose of the Study:
- To test if saccadic and vergence eye movement subsystems utilize extraretinal signals.
- To evaluate feed-forward and feedback models of eye movement control using a remembered-target double-step paradigm.
Main Methods:
- Subjects performed binocular refixations to remembered target positions in darkness using a double-step paradigm.
- Eye movements were recorded and compared against predictions from feed-forward and feedback models.
Main Results:
- A feedback model best explained the direction data for saccadic eye movements.
- The vergence system also showed qualitative agreement with the feedback model, but with lower goodness of fit.
- The gain for the vergence component of the second movement was approximately 60% of the required amplitude.
Conclusions:
- The saccadic and vergence subsystems can utilize nonretinal information from prior movements for direction and depth.
- Reduced vergence gain suggests potential mechanisms operating during the execution stage of motor commands.
- A central control stage comparing desired and current eye position may track movement sequences.