Asymmetries of the saccadic system: A tool to quantify eye dominance strength
Résumé
The saccadic system presents multiple asymmetries. Notably, peak velocities are higher for temporal than for nasal saccades and for centripetal than for centrifugal saccades. We have already shown with binocular recordings (Vergilino-Perez et al., 2012) that participants with weak eye dominance exhibit the classical naso-temporal asymmetry while participants with strong eye dominance exhibit higher peak velocities for a given saccade direction whichever the recorded eye. This categorization of eye dominance strength however remains binary. The current study tests the naso-temporal asymmetry over different conditions so as to provide a finer quantification of eye dominance strength. We ask participants to make centripetal and centrifugal saccades from five different locations. Analyses on the saccadic peak velocities of 48 participants show that the presence of the naso-temporal asymmetry (signing a weak eye dominance) depends on the centripetal or centrifugal nature of the saccade. We propose for the first time a graduated measure of eye dominance strength on a continuum from no eye dominance to very strong eye dominance. Indeed, by testing the naso-temporal asymmetry over different conditions, we assign to each participant a percentage of eye dominance. Potential physiological origins of the asymmetries found in the saccadic system will be discussed.
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