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Laurel Issen, David C. Knill; The weight to spatial memory in visually-guided reaching increases with retinal eccentricity. Journal of Vision 2008;8(6):306. doi: https://doi.org/10.1167/8.6.306.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: When people pick up an object, they can use both the current retinal image of the object and spatial memory to plan the movement. Recent work has shown that people give a higher weight to memory in goal-directed movements when the retinal image is degraded by lower contrast (Brouwer & Knill, JOV, 7(5):6, p1–12). We asked how retinal eccentricity affects the relative contributions of visual and remembered information about object location. Methods: In a virtual environment, two objects appeared on the right side of the screen: a “weapon” and a circular “target” region. The weapon was simulated to be magnetic, so that it would attach itself to the fingertip when touched. Subjects had to move the weapon to the “loading station” on the left side, then move back to touch the circular target. In a third of the conditions, the position of the circular target shifted by one centimeter during the movement to bring the weapon to the loading station (when subjects were fixating the loading station). The screen flickered for 200 msec. to mask the target shift. The weapon / target configuration was located either 14 or 28 degrees of visual angle away form the loading station. Results: Although the final target region was visible in the periphery prior to moving back to touch the target, subjects were significantly biased toward the location where the target had originally appeared. The bias to use spatial memory was significantly more pronounced when the distance between the loading station and the target was 28 degrees than when it was 14 degrees of visual angle. Conclusion: When the target region is visually more eccentric, visual information about target location is degraded. Subjects appropriately weight remembered information about target location differently as a function of target eccentricity.
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