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Alcohol does not affect visual contrast gain mechanisms

Published online by Cambridge University Press:  01 July 1999

PAULINE PEARSON
Affiliation:
Department of Psychology, The University of Western Ontario, London, Ontario, Canada, N6A 5C2 The Retina Foundation of the Southwest, 9900 N. Central Expressway, Suite 400, Dallas, TX 75231, USA.
BRIAN TIMNEY
Affiliation:
Department of Psychology, The University of Western Ontario, London, Ontario, Canada, N6A 5C2 Dean's Office, Social Science Center, The University of Western Ontario, London, Ontario, Canada, N6A 5C2.

Abstract

It has been suggested that acetylcholine plays a role in contrast discrimination performance and the regulation of visual contrast gain (Smith, 1996). Since alcohol has been shown to reduce levels of acetylcholine and contrast sensitivity, the present study measured the effects of alcohol on contrast discrimination and explored whether the deficits could be explained as a consequence of reduction in contrast gain. Detection thresholds and contrast increment thresholds under placebo and alcohol (0.06% BAC) conditions were measured in six volunteers. Alcohol was found to impair both detection and discrimination of only high spatial frequencies. However, when the base contrasts used in the increment threshold task were equal multiples of detection threshold, no alcohol-induced changes in increment thresholds were obtained at any spatial frequency. We conclude that alcohol impairs contrast discrimination performance but that no change in contrast gain mechanisms need be postulated to account for the data.

Type
Research Article
Copyright
1999 Cambridge University Press

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