Exploring the dynamics of light adaptation: the effects of varying the flickering background's duration in the probed-sinewave paradigm

In the probed-sinewave paradign, threshold for detecting a probe is measure d at various phases with respect to a sinusoidally-flickering background. H ere we vary the duration of the flickering background before land after) th e 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 hol ds at both low (1.2 Hz) and middle (9.4 Hz) frequencies because at middle f requencies (but not at low) there is a dc-shift, i.e. probe threshold is el evated at all phases relative to that on a steady background (of the same m ean luminance). We compare our-results to predictions from Wilson's model [ Wilson (1997), Visual Neuroscience, 14, 403-423; Hood & Graham(1998), Visua l Neuroscience, 15, 957-967] of light adaptation. The model predicts the ra pid adaptation, and the de-shift, but not the detailed shape of the probe-t hreshold-versus-phase curve at middle frequencies. (C) 2000 Elsevier Scienc e Ltd. All rights reserved.