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Scott Stevenson, David Arathorn, Qiang Yang, Pavan Tiruveedhula, Nicole Putnam, Austin Roorda; Suppression of retinal image motion due to fixation jitter is directionally biased. Journal of Vision 2010;10(7):845. doi: 10.1167/10.7.845.
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© ARVO (1962-2015); The Authors (2016-present)
Background: Although relative motion thresholds are just a few seconds of arc for adjacent targets (McKee et al. 1990), the overall image motion due to fixation jitter is typically not perceived. An internal copy of the efferent eye movement commands influence motion perception for larger eye movement, but may not have the precision required to correct for fixation jitter. Alternatively, overall retinal image motion may be sensed by early visual mechanisms and then suppressed in perception (Murakami & Cavanagh 1998). Here we ask whether fixation jitter motion suppression is sensitive to the relative direction of eye and retinal image motion. Methods: We decoupled retinal image motion from eye motion using a modified stabilized image technique. An AOSLO with target stabilization was used for both eye tracking and target presentation. Eye motion was recorded and fed back into target position in real time (~4 ms delay) so that the target moved with the eye (conventional stabilization, gain = 1), with the eye but faster (gain = 2 to 4), opposite the eye (gain = -1 to -4), or in a different direction at various gains. Subjects used a matching procedure to set a conventionally viewed jittering target (flat velocity spectrum) to have the same apparent average excursion as the modified stabilized target. Each appeared in unstabilized square 2-degree frames. Results: Gain and direction had a strong effect on perceived motion of the target. Conventionally stabilized targets faded rapidly, as expected. Higher positive gain motion resulted in greater perceived motion, again as expected. Surprisingly, all motions that were in the opposite direction of eye motion (negative gains) appeared as stationary or only very slightly moving. Conclusions: Suppression of retinal image motion due to fixation eye movements includes information about the current eye motion direction, as well as the stimulus motion direction.
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