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Amplitude transition function of human express saccades
A Delinte1, C M Gomez, M F Decostre
1Lab. of Neurophysiology, Universite Catholique de Louvain, Brussels, Belgium.
Neuroscience Research
|January 30, 2002
Summary
Express saccades, short-latency eye movements, are influenced by target presentation during a preparation period. Saccade amplitude results from a weighted average of pre-programmed and target-guided information.
Area of Science:
- Neuroscience
- Ophthalmology
- Cognitive Psychology
Background:
- The gap paradigm is known to elicit express saccades, characterized by short latencies.
- Express saccades are hypothesized to be visually guided, forming a distinct peak in saccadic latency distributions.
Purpose of the Study:
- To investigate the relationship between saccadic amplitude and latency under various experimental conditions.
- To elucidate the underlying mechanisms of anticipatory, express, and regular saccades.
Main Methods:
- Six experiments were conducted comparing saccade amplitudes across different target eccentricities, directions, and predictability.
- Saccadic amplitude was analyzed as a continuous function of latency for varying target eccentricities.
Main Results:
- Saccade preparation during the gap period is influenced by internal cues, determining a baseline amplitude.
- The express saccade latency range represents a transition where the target begins to modify the prepared saccade.
- Saccade amplitude is a weighted average of the internally cued amplitude and the target-defined amplitude, with weighting dependent on saccade latency.
Conclusions:
- Express saccades occur when the target influences an already prepared saccade, resulting in a blend of pre-programmed and visually guided parameters.
- Incorrectly directed pre-programmed saccades cannot be corrected by the target during the express saccade phase, leading to amplitudes similar to anticipatory saccades.
- Regular saccades allow for sufficient time to cancel erroneous pre-programmed movements or adjust the amplitude of correctly directed saccades based on precise target location.