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Melissa Ferreira, Brian Timney; Alcohol induced changes in visual sensitivity: Are they purely sensory?. Journal of Vision 2004;4(8):789. doi: 10.1167/4.8.789.
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Several studies have shown that contrast sensitivity is reduced following acute ingestion of alcohol. The purpose of the present study was to assess the relative contribution of non-sensory factors to this deficit. We did this by assessing performance on a contrast detection task using both conventional threshold procedures and signal detection methods. In three experiments we measured sensitivity for stationary Gabors following either ingestion of a non-alcoholic drink or sufficient alcohol to bring participants' BACs up to 0.08 ml dl-1. In the first experiment we measured contrast sensitivity for patterns of differing spatial frequencies using a staircase procedure. Consistent with previous studies, we found that contrast thresholds increased following alcohol. In the second experiment, we measured detection of a 5 cyc deg-1 pattern of fixed contrast while changing the probability of stimulus occurrence to obtain multiple estimates of d′. The data showed no significant changes in d′ following alcohol. However, the proportion of hits was lower in the alcohol condition. The third experiment was designed to obtain both d′ and a threshold measure from the same data set. We did this by using a method of constants with a single “yes/no” presentation. The probability of a signal on a given trial was set at 50%. This allowed us to use the proportion of hits to construct a psychometric function and the hits and false alarms to calculate d′. As in Experiment 1, contrast thresholds increased following alcohol. However, there were no significant changes in d′ at any of the contrast levels tested. Further analysis showed that both the hit and false alarm rates declined, indicating a shift to a more conservative response criterion. Taken together, these experiments show that, while alcohol increases contrast thresholds when assessed using standard procedures, at least part of this impairment may be attributed to non-sensory factors.
NSERC grant to Brian Timney
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