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Closely spaced, fast dynamic movements in disparity vergence
T L Alvarez1, J L Semmlow, W Yuan
1Department of Biomedical Engineering, Rutgers University, Piscataway, New Jersey 08855, USA.
Journal of Neurophysiology
|February 21, 1998
Summary
This study reveals that eye vergence responses sometimes exhibit double movements, suggesting a control mechanism beyond simple visual feedback. This indicates an internal switching system similar to saccadic eye movements.
Area of Science:
- Ophthalmology
- Neuroscience
- Systems Biology
Background:
- Conflicting theories exist regarding the mediation of symmetrical vergence responses.
- Classical theories propose visual feedback as the primary control mechanism.
- Recent evidence suggests vergence responses may involve non-visually guided components.
Purpose of the Study:
- To investigate the control mechanisms of symmetrical vergence responses.
- To determine if vergence responses exhibit characteristics similar to saccadic eye movements, such as double components.
- To test the hypothesis that vergence control involves an internal switching mechanism.
Main Methods:
- Eye movements were recorded in response to step vergence stimuli (2-10 degrees).
- Net vergence response was calculated by subtracting left and right eye movements.
- Convergent responses exhibiting double fast dynamic components were analyzed.
Main Results:
- Double fast dynamic components were observed in all subjects during high-velocity vergence movements.
- Peak velocities of double movements were lower than single movements.
- A secondary component was generated if the primary component did not reach 80% of stimulus amplitude.
- Dynamics and timing of high-velocity components were consistent with a single controller mechanism.
Conclusions:
- The presence of double high-velocity movements supports an internal, switching control mechanism for vergence.
- These findings challenge theories relying solely on visual feedback for vergence control.
- Vergence control may share similarities with the control mechanisms of saccadic eye movements.