Determinants of adaptation rate in the visual motion aftereffect L C van Dam, M Ernst |
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Cognitive Neurosciences, Bielefeld University, Germany
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| The motion aftereffect is often explained by motion sensitive neurons decreasing their firing rate with prolonged stimulation. Much less is known how the perceived motion aftereffect changes over time with prolonged exposure and how this is influenced by motion uncertainty. To answer this question, we investigate how different types of noise influence the rate of visual motion adaptation perceptually. Participants watched sequences of alternating adaptation (3 sec) and test stimuli (0.5 sec) which both consisted of randomly distributed dots. For the adaptation stimulus, dots could either all be moving in the same direction with the same speed (no noise) or moving in several different directions (noise on direction) or at several different speeds (noise on speed). Test stimuli consisted of limited-life-time dots without any specific movement direction or speed. Participants reproduced the motion perceived for test stimuli on a graphics tablet, thus indicating both aftereffect direction and strength. We found that noise within the stimulus slows down the adaptation rate. Furthermore, when switching between different levels of noise, the noise before such a switch influenced adaptation rates after the switch. These results indicate that current as well as past motion uncertainty affects the adaptation rate in the visual motion aftereffect. |
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