ABSTRACT
While a number of behavioural studies have been conducted to investigate the acute effects of amphetamines on tasks of attention and information processing, there is currently a scarcity of research concerning their electrophysiological effects in healthy adults. It is also unclear as to whether amphetamines exert effects on stimulus evaluation or response selection. In two studies, independent groups of twenty healthy illicit stimulant users aged between 21 and 32 years were administered 0.42 mg/kg d-amphetamine versus placebo, and 0.42 mg/kg d-methamphetamine versus placebo respectively, and completed an auditory oddball task on two separate testing days. A 62-channel EEG was recorded during the completion of the task, and the effects of amphetamines on N200 and P300 ERP components were analysed. d-amphetamine significantly decreased reaction time, improved accuracy, and reduced the latency of the P300 component relative to placebo, while having no effect on the N200 component. d-methamphetamine had no effect on reaction time, accuracy or the P300 component, but reduced the amplitude of the N200 component, relative to placebo. It was concluded that there is tentative support to suggest that d-amphetamine at a dose of 0.42 mg/kg may enhance speed of information processing while d-methamphetamine at a dose of 0.42 mg/kg may reflect changes to stimulus evaluation.
Subject(s)
Brain Waves/drug effects , Central Nervous System Stimulants/pharmacology , Dextroamphetamine/pharmacology , Evoked Potentials/drug effects , Methamphetamine/pharmacology , Acoustic Stimulation , Adult , Analysis of Variance , Dose-Response Relationship, Drug , Electroencephalography , Female , Humans , Male , Neuropsychological Tests , Reaction Time/drug effects , Young AdultABSTRACT
RATIONALE: Extracts of Bacopa monniera have been reported to exert cognitive enhancing effects in animals. However, the effects on human cognition are inconclusive. OBJECTIVE: The current study examined the chronic effects of an extract of B. monniera (Keenmind) on cognitive function in healthy human subjects. METHODS: The study was a double-blind placebo-controlled independent-group design in which subjects were randomly allocated to one of two treatment conditions, B. monniera (300 mg) or placebo. Neuropsychological testing was conducted pre-(baseline) and at 5 and 12 weeks post drug administration. RESULTS: B. monniera significantly improved speed of visual information processing measured by the IT task, learning rate and memory consolidation measured by the AVLT (P<0.05), and state anxiety (P<0.001) compared to placebo, with maximal effects evident after 12 weeks. CONCLUSIONS: These findings suggest that B. monniera may improve higher order cognitive processes that are critically dependent on the input of information from our environment such as learning and memory.