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Adaptation to one perceived motion direction can generate multiple velocity aftereffects

Gekas, Nikos; Mamassian, Pascal


Pascal Mamassian


Sensory adaptation is a useful tool to identify the links between perceptual effects and neural mechanisms. Even though motion adaptation is one of the earliest and most documented aftereffects, few studies have investigated the perception of direction and speed of the aftereffect at the same time, that is the perceived velocity. Using a novel experimental paradigm, we simultaneously recorded the perceived direction and speed of leftward or rightward moving random dots before and after adaptation. For the adapting stimulus, we chose a horizontally-oriented broadband grating moving upward behind a circular aperture. Because of the aperture problem, the interpretation of this stimulus is ambiguous, being consistent with multiple velocities, and yet it is systematically perceived as moving at a single direction and speed. Here we ask whether the visual system adapts to the multiple velocities of the adaptor or to just the single perceived velocity. Our results show a strong repulsion aftereffect, away from the adapting velocity (downward and slower), that increases gradually for faster test stimuli as long as these stimuli include some velocities that match some of the ambiguous ones of the adaptor. In summary, the visual system seems to adapt to the multiple velocities of an ambiguous stimulus even though a single velocity is perceived. Our findings can be well described by a computational model that assumes a joint encoding of direction and speed and that includes an extended adaptation component that can represent all the possible velocities of the ambiguous stimulus.

Journal Article Type Article
Acceptance Date Apr 13, 2021
Online Publication Date May 18, 2021
Publication Date 2021-05
Deposit Date Dec 7, 2021
Publicly Available Date Dec 7, 2021
Journal Journal of Vision
Publisher Association for Research in Vision and Ophthalmology
Peer Reviewed Peer Reviewed
Volume 21
Issue 5
Article Number 17
Public URL


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