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Lisa M Kroell, David Aagten-Murphy, Paul M Bays; Resource limitations in transsaccadic integration. Journal of Vision 2019;19(10):12c. doi: https://doi.org/10.1167/19.10.12c.
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Saccadic eye movements cause large-scale transformations of the image falling on the retina. Rather than starting visual processing anew after each saccade, it has been proposed that new information is integrated with an existing representation of visual input preceding the saccade. Crucially, the relative contribution of each source of information is weighted according to its precision. We reasoned that, if pre-saccadic input is maintained in a resource-limited store such as visual working memory, its precision will depend on the number of items in the pre-saccadic scene, and their priority for attention. We asked observers to report the color of a disk visible both before and after a saccade by clicking on a color wheel. The color changed imperceptibly during the saccade, and we examined where the mean reported color fell on the continuum between pre- and post-saccadic values. We observed a monotonic increase in bias towards the post-saccadic color value as the number of items in the pre-saccadic display increased from 1 to 4, consistent with an increased weighting of the post-saccadic input as precision of the pre-saccadic representation declined. In a second experiment, we investigated if transsaccadic memory resources are preferentially allocated to attentionally prioritized items. An arrow-cue indicated one of four items in the pre-saccadic display that was more likely to be chosen for report after the saccade. As predicted, a valid cue increased response precision and biased responses towards the pre-saccadic color. While adaptive variations in bias indicate that pre- and post-saccadic representations are weighted based on their reliabilities, response variabilities were higher than predicted by an ideal observer model of cue integration. This may be explained by a lingering effect of pre-saccadic memory load on post-saccadic precision. We conclude that transsaccadic integration relies on a limited memory resource that is flexibly distributed between pre-saccadic stimuli.
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