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Spatial Perception around Saccades: Compression, Attention and Visual Space-Time


Paul Reeve < paulr@cim.mcgill.ca >
Universite de Paris V

February 22, 2005 at  11:30 AM
Zames Seminar Room - MC437

The visual brain must maintain the perception of a stable outside world despite the frequent fast, ballistic eye movements known as saccades, which dramatically change the image of the world projected onto the retina about three times per second. Errors in spatial judgements about flashes around saccades have often been used to probe the mechanisms underlying the "remapping" of visual space with each eye movement. Recent related findings include the "presaccadic compression" of visual space, as well as saccade-related "predictive" activity in visual areas of the brain. We have shown that "compression" before saccades applies only to localization of objects in space, and not to distances in that space. I will argue that, rather than directly indicating a functional split in the substrates for different forms of spatial perception; this dissociation may reflect the task-specific dependency of the perceived "space" on a temporally and spatially extended context. I will also discuss the relation of these findings and arguments to the hypothesis that predictive shifts in visual cortex, notably the lateral intraparietal area, explain perisaccadic errors.