Abstract
The motion after-effect (MAE) persists in crowding conditions, i.e., when the adaptation direction cannot be reliably perceived. The MAE originating from complex moving patterns spreads into non-adapted sectors of a multi-sector adapting display (i.e., phantom MAE). In the present study we used global rotating patterns to measure the strength of the conventional and phantom MAEs in crowded and non-crowded conditions, and when attention was directed to the adapting stimulus and when it was diverted away from the adapting stimulus. The results show that: (i) the phantom MAE is weaker than the conventional MAE, for both non-crowded and crowded conditions, and when attention was focused on the adapting stimulus and when it was diverted from it, (ii) conventional and phantom MAEs in the crowded condition are weaker than in the non-crowded condition. Analysis conducted to assess the effect of crowding on high-level of motion adaptation suggests that crowding is likely to affect the awareness of the adapting stimulus rather than degrading its sensory representation, (iii) for high-level of motion processing the attentional manipulation does not affect the strength of either conventional or phantom MAEs, neither in the non-crowded nor in the crowded conditions. These results suggest that high-level MAEs do not depend on attention and that at high-level of motion adaptation the effects of crowding are not modulated by attention.
Highlights
Primate single-cell recordings and human neuroimaging investigations have shown that at the highest levels of motion processing neurons encode the global patterns of motion usually created by forward locomotion through the environment [1,2,3]
A Lilliefors test performed on the percentage of fixational eye movements separately for the two experiments revealed a violation of normality assumption (p = 0.03 and p = 0.0001, respectively)
The repeated-measures ANOVA showed a significant effect of the test condition, the strength of the conventional motion after-affect (MAE) we reported in Experiment 3 was reduced with respect to the conventional MAE of Experiment 1
Summary
Primate single-cell recordings and human neuroimaging investigations have shown that at the highest levels of motion processing neurons encode the global patterns of motion (i.e., optic flow) usually created by forward locomotion through the environment [1,2,3]. Optic flow components such as radial motion (i.e., contracting/expanding), spiral motion and rotational motion are processed by high-level visual areas such as MT and MST [1, 2, 4,5,6,7,8,9,10,11]. In the phantom MAE, adaptation to some sectors of the visual field that contain, e.g., clockwise, counterclockwise, expanding or contracting motion, subsequently
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