Exploring the dynamics of light adaptation: the effects of varying the flickering background's duration in the probed-sinewave paradigm.
In the probed-sinewave paradigm, threshold for detecting a probe is measured at various phases with respect to a sinusoidally-flickering background. Here we vary the duration of the flickering background before (and after) the test probe is presented. The adaptation is rapid; after approximately 10-30 ms of the flickering background, probe threshold is the same as that on a continually-flickering background. It is interesting that this result holds at both low (1. 2 Hz) and middle (9.4 Hz) frequencies because at middle frequencies (but not at low) there is a dc-shift, i.e. probe threshold is elevated at all phases relative to that on a steady background (of the same mean luminance). We compare our results to predictions from Wilson's model [Wilson (1997), Visual Neuroscience, 14, 403-423; Hood & Graham (1998), Visual Neuroscience, 15, 957-967] of light adaptation. The model predicts the rapid adaptation, and the dc-shift, but not the detailed shape of the probe-threshold-versus-phase curve at middle frequencies.
Wolfson
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Department of Psychology, Columbia University, Mail Code 5501, New York, NY 10027, USA. sabina@psych.columbia.edu
Graham
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D000221:Adaptation, Ocular / Q000502:physiology*; D015350:Contrast Sensitivity / Q000502:physiology*; D005425:Flicker Fusion; D006801:Humans; D008432:Mathematical Computing