A temporal model for early vision that explains detection thresholds for light pulses on flickering backgrounds

Abstract

A model is presented for the early (retinal) stages of temporal processing of light inputs in the visual system. The model consists of a sequence of three adaptation processes, with two instantaneous nonlinearities in between. The three adaptation processes are, in order of processing of the light input: a divisive light adaptation, a subtractive light adaptation, and a contrast gain control. Divisive light adaptation is modeled by two gain controls. The first of these is a fast feedback loop with square-root behavior, the second a slow feedback loop with logarithm-like behavior. This can explain several aspects of the temporal behavior of photoreceptor outputs. Subtractive light adaptation is modeled by a high-pass filter equivalent to a fractional differentiation, and it can explain the attenuation of low frequencies observed in ganglion cell responses. Contrast gain control in the model is fast (Victor, 1987), and can explain the decreased detectability of test signals that are superimposed on dynamic backgrounds. We determine psychophysical detection thresholds for brief test pulses that are presented on flickering backgrounds, for a wide range of temporal modulation frequencies of these backgrounds. The model can explain the psychophysical data for the full range of modulation frequencies tested, as well as detection thresholds obtained for test pulses on backgrounds with increment and decrement steps in intensity.

Exploring Visual Adaptation at High Intensity Levels with a Flash-Probe Paradigm

“…Research has been targeted at a full understanding of the temporal dynamics of these adaptation processes; at least to the extent that the processes can be modeled with sufficient accuracy, to serve as input to models of higher-level visual processes. 8 Historically, to investigate temporal effects in light adaptation, both aperiodic light stimuli, [1][2][3] and periodic stimuli, 4,[21][22][23] , including the probe-sinewave paradigm, 5,6,10,[24][25][26] have been used. These studies have both driven the development of, and challenged, computational models of visual adaptation; often a model based on one paradigm was not able to predict the results of another.…”

“…8 In a recent review of probe-sinewave studies, Wolfson and Graham 7 tested existing models of light adaptation dynamics with probe-sinewave data. They concluded that the model of Snippe et al 10,11 was most attractive, primarily because it correctly predicts most of the probesinewave effects very well. Figure 4 shows how the increment thresholds (as measured with a probe stimulus) vary in the presence of the flashing adapting background.…”

“…In a recent review of probed-sinewave experiments investigating the dynamics of light adaptation, Wolfson and Graham (2006) challenged existing models of light adaptation dynamics with probe-sinewave data and found that the model of Snippe et al 10,11 correctly predicts most of the probe-sinewave effects very well.…”

“…The model introduced by Wilson 12 modified by Hood & Graham 27 and Snippe, Poot, & van Hateren 10,11 have been shown to be able to fit both sets of results. 7 The latter model has previously been regarded as most attractive because it predicted most of the probe-sinewave effects very well.…”

Processing of Natural Temporal Stimuli by Macaque Retinal Ganglion Cells

“…It assumed that MC cells receive summed input from L-and M-cones in a ratio of 1.6:1. The model consists of an initial luminance gain control (Lankheet et al, 1993;Snippe et al, 2000;Smith et al, 2001), followed by a compressive nonlinearity. These may represent outer retinal mechanisms.…”