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Peter Smith, Leon McLin, Laura Barnes, Bret Rogers; Exploring the dynamics of light adaptation by measuring sensitivity against a flickering background. Journal of Vision 2007;7(9):270. doi: 10.1167/7.9.270.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction. Previous studies of the dynamics of light adaptation have used a probe-sinewave paradigm, where the threshold for detecting a probe flash is measured at various phases with respect to a sinusoidally modulated background. Our interest is in the temporal changes in visual adaptation that occur during exposure to a train of brief, high intensity flashes. To investigate this we have used a flash-probe paradigm, where the sinusoidally modulated background is replaced with a flashing background. Methods. Increment thresholds were measured for a test stimulus (10 ms) presented at various times (phases) during a periodic flickering background (10 ms, 1 to 64 Hz) while the average power in the flickering background was held constant (2.8 X 108 td). The results can be plotted as threshold for probe detection versus phase curves, from which summary measures, such as the peak-to-trough distance and the dc level, can be derived. Results. In general, probe threshold varied sinusoidally and the effects of the flickering background frequency on the summary measures were very similar to those from other laboratories where the background was modulated sinusoidally: as pulse frequency increased, the average threshold for detection of the probe increased and the peak-to-trough distance decreased. Conclusions. In traditional probe-sinewave experiments the duty cycle for the pulses is 50%. In our experiments, the pulse duration was held constant and so the duty cycle increased with frequency. Despite these differences the summary data patterns are very similar. These data are being used to test existing models of visual adaptation.
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