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Saccadic compensation for smooth eye and head movements during head-unrestrained two-dimensional tracking
1Center for Systems Engineering and Applied Mechanics, Université catholique de Louvain, Louvain-la-Neuve, Belgium.
Journal of Neurophysiology
|November 20, 2009
Summary
Spatial updating during head movements uses saccades to compensate for gaze shifts. Longer saccade latency and greater eye movement contribute to better compensation, similar to head-restrained conditions.
Area of Science:
- Neuroscience
- Vision Science
- Motor Control
Background:
- Spatial updating allows tracking objects during self-motion.
- Spatial constancy in vision is well-studied under head-restrained conditions.
- During head-restrained pursuit, saccades use extraretinal signals for object updating.
Purpose of the Study:
- Investigate if saccades compensate for movements during head-unrestrained smooth pursuit.
- Determine factors influencing spatial updating accuracy with head motion.
- Compare compensation mechanisms in head-unrestrained versus head-restrained conditions.
Main Methods:
- Subjects performed head-unrestrained smooth pursuit in darkness.
- A brief target flash occurred during pursuit, requiring saccadic eye movements.
- Gaze displacement, saccade latency, and eye/head contributions were analyzed.
Main Results:
- Saccades successfully updated target position, typically using 1-3 saccades.
- Longer saccade latency improved compensation for smooth gaze displacement (62% at 400ms).
- Higher eye contribution to gaze displacement correlated with better overall compensation.
Conclusions:
- Saccadic compensation mechanisms during head-unrestrained pursuit are similar to head-restrained conditions.
- Compensation depends on saccade latency and the proportion of eye movement.
- Head oscillation frequency influences compensation, potentially via vestibuloocular reflex (VOR) gain modulation.
