ABSTRACT
During rapid eye movements, or saccades, stable vision is maintained by active reduction of visual sensitivity. The site of this saccadic suppression remains uncertain. Here we show that phosphenes--small illusory visual perceptions--induced by transcranial magnetic stimulation (TMS) to the human occipital cortex are immune to saccadic suppression, whereas phosphenes induced by retinal stimulation are not, thus providing direct physiological evidence that saccadic suppression occurs between the retina and the occipital visual cortex.
Subject(s)
Retina/physiology , Saccades/physiology , Visual Cortex/physiology , Adult , Electromagnetic Fields , Humans , Phosphenes/physiology , Sensory Thresholds/physiology , Visual Perception/physiologyABSTRACT
Around the time of saccadic eye movements, briefly presented stimuli are seen to be displaced from their real positions. The direction of the displacement is always towards the saccadic target, resulting in a compression of visual space (Nature 386 (1997) 598). To examine whether the compression may be used by the visual system to aid performance, we measured sensitivity for detecting horizontal and vertical Glass patterns around the time of saccades. Sensitivity to widely spaced horizontal Glass patterns improved slightly during the period just prior to making a horizontal saccade, while sensitivity to vertical patterns was impaired by the saccade. The results provide further evidence for compression in the direction of the saccade at saccadic onset, and show that it does not only affect the apparent position of visual stimuli, but can also improve performance on a visual task.
