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Doris Braun, Alexander Schütz, Karl Gegenfurtner; Changes in visual sensitivity during smooth pursuit and saccadic eye movement. Journal of Vision 2015;15(12):1022. doi: https://doi.org/10.1167/15.12.1022.
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Eye movements, attention and adaptation adjust visual sensitivity continuously. In particular, during the execution of saccades, visual sensitivity is reduced by an active process suppressing low-frequency luminance stimuli, but not isoluminant color stimuli (Burr, Morrone & Ross, 1994). During smooth pursuit, there is a small decrease in sensitivity for the detection of low-frequency luminance stimuli, but sensitivity to colored stimuli is actually improved (Schütz, Braun, Kerzel & Gegenfurtner, 2008). Here we investigated if these sensitivity adjustments interact when making saccades to moving targets. As a baseline, contrast thresholds were determined for the detection of a red isoluminant line flashed for 8 ms on a gray screen at an eccentricity of 2 degs above or below a central fixation point . Then the detection performance for the horizontal line was measured during smooth pursuit, saccades to stationary and saccades to moving targets. The target either moved horizontally at 11 degs/s after a small step in the opposite direction, was suddenly displaced left- or rightward by 13 deg, or moved horizontally after a 11 deg displacement. The large target steps were chosen to equate saccade amplitudes across conditions. Line detection was measured at two fixed contrasts at different points in time relative to the onset of the eye movement target. Consistently with earlier results, we found a steady increase in sensitivity to isoluminant targets during step-ramp pursuit. The time course of sensitivity for isoluminant stimuli was quite similar for static and moving saccade targets. There was no performance increase before the beginning of pursuit. Contrary to our expectations, three out of our five observers showed a marked saccadic suppression for isoluminant targets. Whatever sensitivity improvement there is during pursuit eye movements, it is suspended during the initial saccade to a moving target.
Meeting abstract presented at VSS 2015
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