N. Sherwood

Separate and combined effects of the social drugs on psychomotor performance

Ten female subjects (five smokers and five non-smokers) performed a choice reaction time task (CRT), a compensatory tracking task (CTT), a short-term memory task (STM) and were tested for their critical flicker fusion threshold (CFF) at set points over 4 h after the administration of each possible combination of nicotine (2 mg gum or placebo), caffeine (250 mg capsule or placebo) and alcohol (30 g or placebo). Memory and motor function were shown to be facilitated by nicotine or caffeine, and the debilitating effects of alcohol were frequently antagonised by either drug. In spite of the differences in their neuropharmacological actions, combinations of nicotine, caffeine and alcohol may be compared through their effects on common information processing mechanisms involved in psychomotor performance.

Psychomotor performance in smokers following single and repeated doses of nicotine gum

The psychomotor effects of single and repeated doses of 2 mg nicotine gum were investigated in 13 regular smokers who had abstained from tobacco overnight. In comparison to baseline, a first dose of nicotine led to significantly raised critical flicker fusion thresholds, faster motor reaction times, improved compensatory tracking performance, and faster short-term memory reaction times. Performance after a second and third dose of nicotine remained significantly improved on all measures in comparison to baseline, and absolutely improved when comparing first and third nicotine doses on measures of sensorimotor performance. Throughout, comparisons with a placebo gum condition confirmed that these effects were genuine and not subject to the development of acute nicotine tolerance, suggesting that the enhancement of psychomotor performance experienced by smokers after a first cigarette may be maintained by repeated smoking.

Effects of cigarette smoking on performance in a simulated driving task

A double-blind study was conducted to investigate the psychomotor effects of cigarette smoking on a 1-hour computer-based simulation of driving comprising continuous tracking and brake reaction time tasks. Twelve minimally abstinent smoker subjects were asked to operate the simulator on four occasions while smoking single cigarettes yielding varying levels of nicotine (< 0.1, 0.6, 1.0 or 2.1 mg) but similar levels (8-10 mg) of tar. Data were transformed with regard to baseline scores to counter day-to-day differences in performance and showed brake reaction times to be improved after all active treatments (p < 0.01) but tracking accuracy to be enhanced after the two cigarettes of middle strength alone (p < 0.05). These results suggest that, among smokers cigarette smoking may improve driving performance and that there may exist an optimal nicotine dose for the enhancement of cognitive and psychomotor function.

Comparison of Five Anxiolytic Benzodiazepines on Measures of Psychomotor Performance and Sleep

The behavioural toxicity of five anxiolytic benzodiazepines was examined in 28 volunteers who were studied in two groups of 14 subjects each. Each drug was taken nocte for 7 days, with a 4-week washout period between drugs. Assessments of psychomotor performance and sleep were made the morning following the first administration and the morning following the last administration. Comparisons of drug effect magnitudes using Cohens d scores suggest that effects on psychological function should be considered as central to the selection and use of such compounds.

Effects of Nicotine Gum on Short-Term Memory

To investigate the effects of nicotine on memory function, 20 subjects (10 non-smokers and 10 smokers who had been allowed to smoke normally until testing) attended the laboratory at their “preferred nicotine level” and completed a short-term memory task (memory scanning) at set points for 4 hours after the administration of 2mg or 0mg (placebo) nicotine polacrilex gum. The results suggest that nicotine enhanced memory reaction time performance (P>0.01) when subjects were probed for information already present in short-term memory (correct positive responses) but had no effect on reaction time when the information was absent from memory (correct negative responses). It is suggested that nicotine facilitates the processing of stimulus information in short-term memory.

Comparative behavioural toxicity of the selective serotonin reuptake inhibitors

The psychopharmacological profiles of several selective serotonin reuptake inhibitors (SSRIs) were compared and their behavioural toxicity contrasted both to placebo and the tricyclic antidepressants dothiepin and amitriptyline. On measures of central nervous system arousal (critical flicker fusion), psychomotor speed (choice reaction time), skilled performance (compensatory tracking) and subjective ratings of sedation (line analogue rating scales), the tricyclic compounds clearly impaired performance and led to higher ratings of sedation. While the SSRIs were generally clear of these gross effects, there were quantifiable differences between the compounds, seen mainly as an increase in central nervous system arousal. It remains to be established whether these minor differences have any clinical relevance.

Amnestic effects of triazolam and other hypnotics

1. The effects of a number of hypnotics were compared to a range of results collected for triazolam on objective measures of CNS sedation (critical flicker fusion) and short-term memory function (memory scanning). 2. Assessments taken after the drugs had been administered but prior to the onset of sleep showed that in comparison to placebo most of the compounds were effective sedatives and this correlated highly (r = 0.734, p < 0.04) with amnestic effects found at the same time, suggesting that general CNS sedation is a major component of anterograde amnesia. 3. Residual effects assessed the morning after the hypnotics had been used showed a similar relationship (r = 0.896, p < 0.005). 4. The distribution of results indicates that 0.25 mg triazolam has an acute amnestic profile which is similar to other hypnotics, but possesses a distinct lack of residual effects.

The Comparative Psychopharmacology of Nicotine

The psychopharmacological profile of nicotine was compared with those of 25 other substances including other social drugs and medicinal compounds. The sizes of effect of drugs on various items in a standardised test battery were calculated and ranked. It was shown that nicotine, in contrast to the other substances had small, specific, positive effects and a negative rating of behavioural toxicity.