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Ra�l Luna, Ignacio Serrano-Pedraza; Motion discrimination is impaired when coarse and fine-scale patterns move together at the same speed. Journal of Vision 2016;16(12):659. doi: https://doi.org/10.1167/16.12.659.
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Motion direction discrimination at short durations is impaired when a static coarse-scale pattern is added to a moving fine-scale pattern. It has been suggested that this impairment is a consequence of an antagonism between motion-sensors tuned to fine and coarse scales (high and low spatial frequencies) (Serrano-Pedraza, Goddard & Derrington, Journal of Vision, 2007). However, when a static fine-scale pattern is added to a moving coarse scale pattern, motion discrimination is facilitated (Serrano-Pedraza, et al, Journal of Vision, 2013). In this study we wanted to test whether this impairment or facilitation occurs when both coarse- and fine-scales move together at the same speed. We measured duration thresholds for 7 participants using adaptive Bayesian staircases in a motion direction discrimination task. Two types of stimuli were used: simple drifting vertical-Gabor patches and complex vertical-Gabor patches resulting from the addition of two Gabor patches of different spatial frequencies. We tested for the simple Gabor patches: 0.25,0.75,1,1.5,2,3,6c/deg. For the complex stimuli we tested the following pairs of spatial frequencies: 0.25-0.75c/deg; 0.75-1.5c/deg; 1-3c/deg; and 2-6c/deg. The speed of the stimuli was always 2deg/sec, the contrast 0.275 and the size Sxy=2deg. Results for simple stimuli showed a reduction of duration thresholds as a function of the spatial frequency. Duration thresholds obtained with complex stimuli were, in all cases, similar to the duration thresholds of the component with the lower spatial-frequency of the pair. This suggests that motion discrimination was driven by the lower spatial-frequency component. However, in a second experiment, reducing the contrast of the lower spatial-frequency component also showed that duration thresholds for complex stimuli, in particular the pairs 0.75-1.5c/deg and 1-3c/deg, were higher than the duration thresholds obtained for each single component. These results are consistent with an inhibitory interaction between motion-sensors tuned to coarse and fine scales.
Meeting abstract presented at VSS 2016
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