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Tobias Otte; Psychophysical evidence for long-range influence on foveal adaptation. Journal of Vision 2006;6(6):703. doi: 10.1167/6.6.703.
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In 1985, Valberg, Lee, Tigwell & Creutzfeld showed that intensity-response curves of cells in the macaque geniculate nucleus are shifted to higher ranges when a white annulus is added around the adaptation field of the recorded cells. We found psychophysically that a flash-induced foveal afterimage appears light when the background is surrounded by a dark annulus of 8 deg inner radius, and dark when the surrounding annulus is light. We conclude that the annulus affects the afterimage by a long-range neural signal (Otte, Valberg & Spillmann, 2005). Results differ from the “periphery-effect” (McIlwain, 1964) and similar lateral effects. Whereas these effects are elicited by a strong motion signal, the polarity of the afterimage depends on the luminance in the surround.
Afterimages elicited by a strong light are known to change their brightness in counter-phase to the background. Here I present a model demonstrating how the luminance in the periphery affects the brightness of a foveal afterimage, assuming that the surround signal alters the adaptation level of the foveal cells as suggested by Valberg et al. (1985). This model strengthens the correlation between the neurophysiological results by Valberg et al. and our psychophysical findings.
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