Forty-four Years of Studying Light Adaptation Using the Probed-sinewave Paradigm

Here we examine results from 44 years of probed-sinewave experiments investigating the dynamics of light adaptation. We also briefly examine four models that have been tested against the results. In these experiments, detection threshold is measured for a test stimulus superimposed at various times (phases) on a sinusoidally flickering homogeneous background. The results can be plotted as probe-threshold versus phase curves. Overall, the curves from different laboratories are remarkably similar given the substantial differences in experimental parameters. However, at medium frequencies of background flicker, there are some differences between the majority of the studies and a minority of two. An examination of the full set of results suggests that the differences are not as significant as they first appear and that the experimental condition leading to the differences is the use of long wavelength light in the two minority studies. Of the four models that have been tested, two fail to predict important features of the results, another is critically dependent on a mechanism unlikely to exist in the appropriate physiology, and the last seems quite promising.