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Adela SY. Park, Alexander C. Schütz; Selective enhancement of motion perception for small, low contrast stimuli immediately after saccadic eye movements. Journal of Vision 2020;20(11):1027. doi: https://doi.org/10.1167/jov.20.11.1027.
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© ARVO (1962-2015); The Authors (2016-present)
Saccadic eye movements have drastic consequences for motion perception: during saccades, the perception of visual motion is attenuated by the fast motion of the eyes (Burr & Ross, 1982; Castet & Masson, 2000). After saccades, reflexive tracking movements in response to large field motion are enhanced and this response is well correlated with post-saccadic enhancement of neural activity in the primate motion processing areas (Takemura & Kawano, 2006). Currently it is unclear how this postsaccadic enhancement is achieved. Therefore, we tested if the enhancement is related to the balance of centre-surround antagonism in motion processing, favouring spatial summation at low contrasts and surround suppression at high contrasts (Tadin et al., 2003).
We investigated the influence of saccades on motion direction discrimination by presenting Gabor stimuli following horizontal saccadic eye movements. The Gabors had a spatial frequency of 1 cpd and were drifting vertically inside a stationary aperture at a speed of 2 deg/s. We measured minimum duration thresholds for small and large (0.7 and 5 deg diameter) and low and high contrast (2.8 and 92%) Gabor stimuli presented immediately after saccade offset or with a delay of 300 ms.
For small, low contrast stimuli, motion discrimination thresholds were lower directly after the saccade than 300 ms later. This enhancement of motion sensitivity was not present for large stimuli or high contrast stimuli, resulting in a smaller amount of spatial summation for low contrast stimuli. Our results could be interpreted in the sense that the amount of spatial summation is transiently reduced after saccades or that a non-linearity in motion processing leads to the selective enhancement of sensitivity for weak, i.e. small and low contrast stimuli immediately after saccades. Either way, visual sensitivity is altered after saccades, possibly to maximize sensitivity for the saccade target as the primary object of interest.
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