Abstract
Observers made a saccade between two fixation markers while a probe was flashed sequentially at two locations on a side screen. The first probe was presented in the far periphery just within the observer's visual field. This target was extinguished and the observers made a large saccade away from the probe, which would have left it far outside the visual field if it had still been present. The second probe was then presented, displaced from the first in the same direction as the eye movement and by about the same distance as the saccade step. Because both eyes and probes shifted by similar amounts, there was little or no shift between the first and second probe positions on the retina. Nevertheless, subjects reported seeing motion corresponding to the spatial displacement not the retinal displacement. When the second probe was presented, the effective location of the first probe lay outside the visual field demonstrating that apparent motion can be seen from a location outside the visual field to a second location inside the visual field. Recent physiological results suggest that target locations are “remapped” on retinotopic representations to correct for the effects of eye movements. Our results suggest that the representations on which this remapping occurs include locations that fall beyond the limits of the retina.
Highlights
With our head and eyes steady, our normal binocular vision covers a visual field of about 200 to 220 degrees of visual angle [1]
We reported here that observers do see apparent motion across a saccade even though its first location falls outside the visual field by the time the second position is presented
On 75% of trials, motion was seen after the saccade from this extra-retinal location to a new location within the visual field, indicating that the visual system keeps track of locations that move outside the visual field due to saccades
Summary
With our head and eyes steady, our normal binocular vision covers a visual field of about 200 to 220 degrees of visual angle [1]. Active cortical processes have been discovered in several visuo-motor areas (e.g., LIP, SC, FEF) that predict the retinal locations that attended objects will have following each eye movement [3,4,5,6,7] This visual areas are organized in retinotopic coordinates [8,9], so this updating process, called ‘‘remapping’’ [3], keeps track of target locations in the world despite the constant shifts on the retina. These processes may take advantage of a copy of the motor command for each eye movement (efference copy or corrolary discharge, [10,11,12]) to predict the new, post-saccadic target location. We will use a motion paradigm where observers report whether or not a probe appears to move even though one position falls, after an eye movement, outside the visual field
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