van Beers R J, Haggard P, Wolpert D M, 2000, "Localisation during smooth-pursuit eye movements: different retinal areas are integrated with gaze signals from different moments in time" Perception 29 ECVP Abstract Supplement
Localisation during smooth-pursuit eye movements: different retinal areas are integrated with gaze signals from different moments in time
R J van Beers, P Haggard, D M Wolpert
To localise an object in space, the object's retinal location has to be integrated with the gaze direction from the same moment in time. It is usually assumed that all retinal input is integrated with a single gaze signal. During smooth-pursuit eye movements, the images of static objects move on the retina. Mateeff et al (1991 Vision Research 31 2235 - 2237) showed that in this situation perceptual latencies are shorter for motion toward the fovea than for motion away from it. Such differential latencies should disrupt position constancy during pursuit. Nevertheless, everyday experience tells us the visual world is stable.
To find out how position constancy is maintained during smooth pursuit, we studied where subjects localised visual targets presented either ahead of or behind the fovea. We presented either static targets, which have different latencies in these two zones, or flashed targets, which do not. Our results show that static stimuli are localised correctly irrespective of their retinal location. Flashes ahead of the fovea, however, are perceived too far ahead, whereas flashes behind the fovea are localised correctly. This suggests that the brain maintains position constancy by integrating different retinal areas with gaze signals from different moments in time.
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