Abstract
Microsaccades are involuntary eye movements occurring naturally during fixation. In this study, microsaccades were investigated under monocularly and binocularly stimulated conditions with respect to their directional distribution and rate signature, that refers to a curve reporting the frequency modulation of microsaccades over time. For monocular stimulation the left eye was covered by an infrared filter. In both stimulation conditions, participants fixated a Gabor patch presented randomly in orientation of 45° or 135° over a wide range of spatial frequencies appearing in the center of a monitor. Considering the microsaccadic directions, this study showed microsaccades to be preferably horizontally oriented in their mean direction, regardless of the spatial characteristics of the grating. Furthermore, this outcome was found to be consistent between both stimulation conditions. Moreover, this study found that the microsaccadic rate signature curve correlates between both stimulation conditions, while the curve given for binocular stimulation was already proposed as a tool for estimation of visual performance in the past.Therefore, this study extends the applicability of microsaccades to clinical use, since parameters as contrast sensitivity, has been measured monocularly in the clinical attitude.
Highlights
Fixation on a visual target is not stable, instead such a fixation is accompanied by small involuntary eye movements – fixational eye movements (FEMs) (Martinez-Conde, Macknik, & Hubel, 2004; Otero-Millan, Macknik, & Martinez-Conde, 2014; Martina Poletti & Rucci, 2016; Rolfs, 2009; Rolfs, Kliegl, & Engbert, 2008; Essig, P., Leube, A., Rifai, K., & Wahl, S. (2020) Microsaccadic rate signatures correlate under monocular and binocular stimulation conditionsRucci & Poletti, 2015)
The current study showed the evidence of correlated rate signature curves under distinct stimulation conditions in healthy subjects and proposes to use monocularly stimulated microsaccadic rate signature as a tool for estimation of visual sensitivity following the clinical attitude, since such a metric of visual performance as contrast sensitivity has been measured under monocular conditions in the clinical environment
The current study has found the direction of microsaccades as preferably horizontally oriented independently to the orientation of the Gabor patch, as well as for the spatial frequency of that grating
Summary
Fixation on a visual target is not stable, instead such a fixation is accompanied by small involuntary eye movements – fixational eye movements (FEMs) (Martinez-Conde, Macknik, & Hubel, 2004; Otero-Millan, Macknik, & Martinez-Conde, 2014; Martina Poletti & Rucci, 2016; Rolfs, 2009; Rolfs, Kliegl, & Engbert, 2008; Essig, P., Leube, A., Rifai, K., & Wahl, S. (2020) Microsaccadic rate signatures correlate under monocular and binocular stimulation conditionsRucci & Poletti, 2015). Past research showed microsaccades as an indicator for discrimination of the orientation of a contrast stimulus featured by higher spatial frequency, not for the stimulus of lower spatial frequency (Rucci, Iovin, Poletti, & Santini, 2007) Those fixational saccades indicated sensitivity in the rate signature curve for small changes in contrast using a spatially oriented pattern with fixed spatial frequency of 0.33cpd (cycles/degree) (Scholes, McGraw, Nyström, & Roach, 2015), as well as for larger changes in contrast using a spatially oriented grating with fixed spatial frequency of 3.0cpd (Bonneh, Adini, & Polat, 2015). On the other hand, Denniss, et al 2018 measured contrast sensitivity under monocularly
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