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Teresa D. Hernandez, Carmel A. Levitan, Clifton M. Schor, Martin S. Banks; Hand pointing is accurate following adaptation of saccadic gain. Journal of Vision 2005;5(8):436. doi: https://doi.org/10.1167/5.8.436.
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© ARVO (1962-2015); The Authors (2016-present)
The visual system uses two major sources of information to determine the direction of an object in space: extra-retinal signals from ocular muscles and retinal cues. The influence of extra-retinal signals on estimates of perceived space is unclear. Saccade amplitude can be adapted quickly using a double-step paradigm. Extra-retinal factors are thought to be responsible for the resulting change in saccade size and its influence on perceived direction. An alternative hypothesis is that retinal signals undergo adaptation. In order to determine which of these accounts is correct, we asked subjects to point with the unseen hand to brief visual targets at eccentricities of 5, 10, 12, 15 and 20 degrees. There were two conditions: (1) the subject made a saccade toward the intended target and then pointed towards the remembered target location, and (2) the subject pointed at the flashed target without making a saccade. Subjects performed this task before and after saccade adaptation. Although saccades were adapted to 1/3 of their original size, subjects still pointed towards the correct location of the flashed target under both conditions. This suggests that the assumption of extra-retinal adaptation is correct, and that retinal signals are not altered by double-step saccade adaptation.
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