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Maria Concetta Morrone, Alessandro Benedetto; Rhythmic modulation of human visual sensitivity synchronized with planning of saccades. Journal of Vision 2017;17(10):922. doi: https://doi.org/10.1167/17.10.922.
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Tommasini et al (2015) have shown that voluntary hand movements can induce rhythmic theta-band oscillations in visual contrast sensitivity, a very early visual function, and crucially for stimuli irrelevant to the executed action. The oscillations emerge during the motor planning stage, before the onset of the reaching and grasping movement. Action planning for eye movements and perception are intimately coupled systems. The temporal synchronization between saccadic onset and saccadic suppression is a clear demonstration of this temporal precise link. However, how the brain achieves this close synchronization is still unknown. We investigated the effect of saccades on contrast discrimination sensitivity over a long period stretching over more than 1 second before and after saccade execution. Human subjects made horizontal saccades at will to two stationary saccadic targets separated by 20° degrees. At a random interval, a brief Gabor patch was displayed between the two fixations in either the upper or lower visual field, and the subject had to detect its location. Strong saccadic suppression was measured between −50 and 50 ms from saccadic onset. However, the suppression was systematically embedded in a trough of oscillations of contrast sensitivity and criterion that fluctuated rhythmically in the delta range (at about 3 Hz), commencing about one second before saccade execution and lasting for up to one second after the saccade. The results show that saccadic preparation and oscillations in visual sensitivity are coupled, and the coupling might be instrumental in temporally aligning the initiation of the saccade with the visual suppression.
Meeting abstract presented at VSS 2017
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