A gain-control model relating nulling results to the duration of dynamic motion aftereffects.
Strength of the motion aftereffect (MAE) is most often quantified by its duration, a high-variance and rather 'subjective' measure. With the help of an automatic gain-control model we quantitatively relate nulling-thresholds, adaptation strength, direction discrimination threshold, and duration of the dynamic MAE (dMAE). This shows how the nulling threshold, a more objective two-alternative forced-choice measure, relates to the same system property as MAE-durations. Two psychophysical experiments to test the model use moving random-pixel-arrays with an adjustable luminance signal-to-noise ratio. We measure MAE-duration as a function of adaptation strength and compare the results to the model prediction. We then do the same for nulling-thresholds. Model predictions are strongly supported by the psychophysical findings. In a third experiment we test formulae coupling nulling threshold, MAE-duration, and direction-discrimination thresholds, by measuring these quantities as a function of speed. For the medium-to-high speed range of these experiments we found that nulling thresholds increase and dMAE-durations decrease about linearly, whereas direction discrimination thresholds increase exponentially with speed. The model description then suggests that the motion-gain decreases, while the noise-gain and model's threshold increase with speed.
van de Grind
W A
WA
Department of Biology, Functional Neurobiology, Helmholtz Institute, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands. w.a.vandegrind@bio.uu.nl
Lankheet
M J M
MJ
Tao
R
R
D000222:Adaptation, Physiological / Q000502:physiology; D004192:Discrimination, Psychological / Q000502:physiology; D005366:Figural Aftereffect / Q000502:physiology*; D006801:Humans; D008959:Models, Neurological; D008960:Models, Psychological; D009039:Motion Perception / Q000502:physiology*; D011601:Psychophysics; D012684:Sensory Thresholds / Q000502:physiology; D013997:Time Factors