Abstract
Saccadic suppression describes the reduction of sensitivity to luminance contrasts at low spatial frequencies around the time of saccades. It has been suggested that saccadic suppression is an active neural mechanism. Yet, its site is as yet unclear as is the question whether it acts monocularly or binocularly. Passive explanations have also been put forward which typically postulate that saccadic suppression is caused by the eyes’ high velocity during saccades. If saccadic suppression had a passive origin or if it involved only monocular brain structures, contrast sensititivty should not depend on the movement of the non-stimulated eye during monocular stimulation. Contrast sensitivty was measured psychophysically in a 2AFC task. Human observers performed saccades in depth to visual targets aligned in front of one of the two eyes. This approach resulted in temporally aligned saccades of different size and velocity for the two eyes. In a given trial, we presented a low spatial frequency gabor-patch with variable luminance contrast monocularly either above or below the horizontal meridian to one of the two eyes. Participants indicated the perceived location of the stimulus. Perceptual data were first sorted by saccade velocity. Psychometric curves were next fitted separately for trials in which the stimulus was presented to the slower or the faster eye. Contrast sensitivities were extracted from these fits. When data were analyzed with respect to the eyes’ individual velocity, the sensitivity at a given velocity differed between the faster and slower eye. When analysis was based on the velocity of the faster eye, sensitivities were comparable for both eyes. We conclude that saccadic suppression does not dependent on the physical speed of the eye and must hence rely on an active binocular mechanism
Meeting abstract presented at VSS 2013