Triazolam and ethanol effects on human matching-to-sample performance vary as a function of pattern size and discriminability

Effects of D-amphetamine and ethanol on variable and repetitive key-peck sequences in pigeons

This experiment assessed the effects of d-amphetamine and ethanol on reinforced variable and repetitive key-peck sequences in pigeons. Pigeons responded on two keys under a multiple schedule of Repeat and Vary components. In the Repeat component, completion of a target sequence of right, right, left, left resulted in food. In the Vary component, 4-peck sequences differing from the previous 10 produced food. d-Amphetamine (0.1-3.0 mg/kg, i.m.) was administered in two separate phases, separated by ethanol administration (1.0-2.0 g/kg, i.g.). Under control conditions, measures of variability were high in the Vary component, and lower in the Repeat component. Following administration of the highest dose of d-amphetamine, but not ethanol, response rates decreased in both components. d-Amphetamine and ethanol tended to increase overall sequence variability in the Repeat component, and had less of an effect in the Vary component. Performance in the Repeat component during Phase 2 of d-amphetamine administration was more disrupted than during Phase 1. Measures of variability and repetition based on shifts in the relative frequency distributions of the 16 possible keypeck sequences differed from those based on the overall measure of variability, highlighting the importance of considering both molar and molecular measures when assessing the effects of drugs on reinforced variability and repetition. In addition, the shifts in the relative frequency distribution of response sequences suggest that d-amphetamine produced decrements in repeat performance by decreasing discriminative control within response sequences, whereas ethanol decreased repeat performance by decreasing discriminability between components as well as discriminative control within response sequences.

Errors in performance testing: a comparison of ethanol and temazepam

Both ethanol and benzodiazepines impair psychomotor function. Previous work has suggested that ethanol may have a greater effect on errors while benzodiazepines may cause greater slowing, but this has not been tested in a direct comparison. We assessed the effects of ethanol, at blood concentrations of approximately 80-100 mg/100 ml, compared to two doses of temazepam (20 mg and 30 mg) on psychomotor speed and accuracy and on long-term memory. Sixteen healthy volunteers (eight male, aged 20-25 years) took part in a four-period, placebo-controlled cross-over study. Performance was evaluated using analysis of covariance (critical significance level, p = 0.05) comparing the areas under the response-time curves. Performance on a psychomotor maze showed an almost complete dissociation, with ethanol leading to a substantial and significant increase in errors with little effect on speed, while temazepam slowed performance with no significant change in accuracy. Other tasks showed a similar pattern, but the dissociation was less complete. Handwriting size was substantially increased by ethanol, but not by temazepam. Information processing capacity and long-term memory formation were reduced by a similar amount both for ethanol and 30 mg temazepam. The faster, more error-prone, behaviour on ethanol than with a similarly impairing dose of temazepam has clear implications for the relative potential of the two drugs to contribute to accidents. The results are also important in understanding the differential effects of drugs with different mechanisms of action on human performance.

Effects of lorazepam on perceptual integration of visual forms in healthy volunteers

We tested whether lorazepam (a benzodiazepine) affects perceptual processes involved in the computation of contour information. Subjects matched incomplete forms whose contour was composed of line segments varying in their spacing and in their alignment. An initial centrally displayed object (a reference) was followed by two laterally displayed pictures, a target and a distractor. The distractor was the mirror-reversed version of the target. In one condition, the reference was always an outline drawing of an object. In another condition, the reference was either an outline drawing or an incomplete form. All subjects were run in both conditions. Lorazepam 0.038 mg/kg induced a larger increase in RTs than the placebo and lorazepam 0.026 mg/kg when the spacing between local contour elements was larger than 10.8' arc and when the line segments were not aligned. Performance was improved in the 0.038 mg/kg lorazepam group when subjects started with the condition in which the reference was always an outline drawing. Performance was not correlated with sedation. These results show that lorazepam impairs visual perception. They are interpreted in terms of impaired binding processes, which can be compensated for by the use of stored object representations. This effect is consistent with electrophysiological studies showing that the neuromediator GABA is involved in perceptual processes.