Alessandro Benedetto and Maria Concetta Morrone
Saccadic suppression is embedded within extended oscillatory modulation of sensitivity,
Journal of Neuroscience 29 March 2017, 37 (13) 3661-3670
Action and perception are intimately coupled systems; one clear case is saccadic suppression, the reduced visibility around the time of saccades, important in mediating visual stability; another is the oscillatory modulation of visibility synchronized with hand action. To suppress effectively the spurious retinal motion generated by the eye movements, it is crucial that saccadic suppression and saccadic onset be temporally synchronous. However, the mechanisms that determine this temporal synchrony are 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 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 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 visual sensitivity oscillations are coupled, and the coupling might be instrumental in temporally aligning the initiation of the saccade with the visual suppression.Significant statementSaccades are known to produce a suppression of contrast sensitivity at saccadic onset and an enhancement after saccadic offset. Here we show that these dynamics are systematically embedded in visual oscillations of contrast sensitivity that fluctuate 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 visual sensitivity oscillations are coupled, and the coupling might be instrumental in aligning temporally the initiation of the saccade with the visual suppression.