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Kevin D Johnston, Brian N Timney; Ethanol-induced changes in Westheimer functions consistent with decreases in lateral inhibition. Journal of Vision 2003;3(9):352. doi: 10.1167/3.9.352.
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Several studies have shown that alcohol modifies inhibitory neural interactions. We used the visual system as a model to determine the possible perceptual consequences of alcohol-induced reductions in inhibition. The rationale is as follows: if alcohol reduces lateral inhibition, then any visual phenomena that rely on such inhibition should show characteristic and predictable changes. We have already shown changes consistent with reduced inhibition in simultaneous contrast and the Hermann Grid Illusion. In the present studies we extended this logic to the Westheimer paradigm. The shape of Westheimer functions is assumed to depend on the relative contribution of the inhibitory surround in centre-surround receptive fields. We obtained these functions under two conditions: 1. consumption of sufficient alcohol to raise subjects' BAC to .08%; 2.consumption of an equivalent volume of fruit juice. Subjects were required to detect a 0.02 s target flash superimposed on a luminance pedestal of varying diameter. The pedestal was superimposed on a background field whose luminance was set 1 log unit beneath that of the pedestal. Functions were obtained on backgrounds that were photopic (0.5 cd m−2), mesopic (0.05 cd m−2), and scotopic (0.005 cd m−2). We predicted that if ethanol reduced lateral inhibition, increment thresholds in the photopic and mesopic conditions should be increased at pedestal diameters within the sensitization and plateau portions of the Westheimer function. Because dark adaptation has been shown to eliminate lateral inhibition, we also predicted that the scotopic Westheimer function should be unaffected. Changes consistent with this prediction were obtained in each condition.
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