Increased sensitivity to speed changes during adaptation to first-order, but not to second-order motion.
Observers adapted to drifting patterns varying either in luminance (first-order pattern), or in contrast (second-order pattern). Sensitivity to increases or decreases in the speed of the first-order pattern increased sharply as adaptation time increased, but sensitivity to speed changes of the second-order pattern remained unchanged throughout the adaptation time. Adaptation of first-order motion mechanisms seems thus to mediate increased sensitivity to variations in speed around the adapting speed. No evidence was found for such effects of adaptation to second-order motion. The observed differences in the effects of adaptation accord well with reports of fundamental differences between after-effects to drifting first- and second-order patterns and are in harmony with models of motion perception emphasizing different mechanisms for the detection of first- and second-order motion.
Kristjánsson
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Vision Sciences Laboratory, Harvard University, William James Hall, 33 Kirkland Street, Cambridge, MA 02138, USA. kristjan@wjh.harvard.edu
D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D015350:Contrast Sensitivity / Q000502:physiology*; D005366:Figural Aftereffect / Q000502:physiology; D006801:Humans; D008029:Lighting; D016015:Logistic Models; D009039:Motion Perception / Q000502:physiology*; D011594:Psychometrics; D013997:Time Factors