reprint (pdf 500K)
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 msec 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 WilsonUs model [Wilson (1997), Vis. Neurosci., 14, 403-423; Hood & Graham (1998), Vis. Neurosci., 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.
Supported by NIH grants EY08459 to Norma Graham and EY06933 to Sabina Wolfson.