Examining brain-cognition effects of ginkgo biloba extract: brain activation in the left temporal and left prefrontal cortex in an object working memory task.

Ginkgo Biloba extract (GBE) is increasingly used to alleviate symptoms of age related cognitive impairment, with preclinical evidence pointing to a pro-cholinergic effect. While a number of behavioral studies have reported improvements to working memory (WM) associated with GBE, electrophysiological studies of GBE have typically been limited to recordings during a resting state. The current study investigated the chronic effects of GBE on steady state visually evoked potential (SSVEP) topography in nineteen healthy middle-aged (50-61 year old) male participants whilst completing an object WM task. A randomized double-blind crossover design was employed in which participants were allocated to receive 14 days GBE and 14 days placebo in random order. For both groups, SSVEP was recorded from 64 scalp electrode sites during the completion of an object WM task both pre- and 14 days post-treatment. GBE was found to improve behavioural performance on the WM task. GBE was also found to increase the SSVEP amplitude at occipital and frontal sites and increase SSVEP latency at left temporal and left frontal sites during the hold component of the WM task. These SSVEP changes associated with GBE may represent more efficient processing during WM task completion.

High-dose glycine impairs the prepulse inhibition measure of sensorimotor gating in humans.

An impaired capacity to filter or 'gate' sensory information is a core deficit in cognitive function associated with schizophrenia. These deficits have been linked in part to N-methyl-d-aspartate (NMDA) receptor dysfunction. An association between high levels of glycine, a positive allosteric modulator of the NMDA receptor, and sensorimotor gating impairments (i.e. prepulse inhibition (PPI) deficit) have been reported in animal models of schizophrenia as well as patients with schizophrenia. This study examined the acute effects of modulating the glycine site of the NMDA receptor (with high-dose glycine) on sensory gating as measured by PPI. Sixteen healthy male subjects (final sample size of 12) participated in a double-blind, placebo-controlled, crossover design in which each subject was tested under two acute treatment conditions separated by at least a 5-day washout period; placebo and 0.8 g/kg glycine. PPI was recorded 45 min post treatment using electromyography of the eye-blink response. Relative to placebo, high-dose glycine significantly impaired sensorimotor gating as demonstrated by a decrease in PPI (t(11) = -2.983, p < 0.05). Administration of a high dose of glycine is associated with impairments in PPI supporting earlier observations in animals and patients with schizophrenia. This result, when taken together with findings in patients, suggests that high synaptic levels of glycine may have some clinically relevant detrimental effects and suggests a potential dissociation of clinical symptomatology and sensory information processing as a function of NMDA receptor modulation in schizophrenia.

The chronic effects of an extract of Bacopa monniera (Brahmi) on cognitive function in healthy human subjects.

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.

An investigation into the acute nootropic effects of Hypericum perforatum L. (St. John's Wort) in healthy human volunteers.

Hypericum perforatum L. (St. John's Wort) is a complex herb that has been used for centuries for its putative medicinal properties, and has current therapeutic relevance as a treatment of mild to moderate depression. Recently, two studies in rodents have suggested that hypericum may also have memory-enhancing effects. It has a complex pharmacology, in that acute administration modulates numerous neurotransmitter systems that have previously been observed to either augment or impair a variety of memory processes in humans. This study aimed to examine whether acute administration of standardized hypericum extract could exert a nootropic effect in normal human subjects. The study employed a double-blind, crossover, repeated-measures design. Twelve healthy young subjects completed the Cognitive Drug Research (CDR) memory battery, following administration of placebo, 900 mg and 1800 mg hypericum (Blackmore's Hyperiforte). The findings suggested that hypericum does not have an acute nootropic effect in healthy humans at these doses. However, there was some evidence for an impairing effect on accuracy of numeric working memory and delayed picture recognition at the higher dose. This observed impairment could be due to a sensitivity of these specific tasks to modulation by neurotransmitters that have been noted to have memory-impairing effects (e.g. y-aminobutyric acid (GABA), serotonin).

Neuropsychological changes after 30-day Ginkgo biloba administration in healthy participants.

Ginkgo biloba extract (EGb) from the world's oldest living tree has been reputed to ameliorate cognitive decline in the elderly and slow cognitive deterioration in patients with dementia of the Alzheimer's type. EGb remains as one of the most popular plant extracts to alleviate symptoms associated with a range of cognitive disorders such as Alzheimer's disease, vascular dementia and age-related amnesic conditions. EGb is known to contain a range of chemically active components that have antagonistic effects on platelet-activating factor, free-radical scavenging activity and direct effects on the cholinergic neurotransmitter system. Recently there has been much speculation, that EGb may act as a 'smart drug' or nootropic agent in the healthy young to improve intelligence. We conducted a 30-d randomized, double-blind, placebo-controlled clinical trial in which 61 participants were administered a battery of validated neuropsychological tests before and after treatment. Statistical analysis indicated significant improvements in speed of information processing working memory and executive processing attributable to the EGb.

Hypericum perforatum (St John's Wort): a non-selective reuptake inhibitor? A review of the recent advances in its pharmacology.

Hypericum possesses a unique pharmacology in that it displays the pharmacology of many classes of antidepressants and new mechanisms not typical of standard antidepressants. The most potent of all its action is the moderate to high potency for inhibition of the reuptake of monoamines, serotonin, dopamine and noradrenaline and the amino-acid neurotransmitters GABA and glutamate. Unlike standard reuptake inhibitors, hypericum exerts this reuptake inhibition non-competitively by enhancing intracellular Na+ ion concentrations. At a receptor level, chronic treatment with hypericum downregulates beta1-adrenoceptor, upregulates post-synaptic 5-HT1A receptors and 5-HT2 receptors. Although the major constituent responsible for the antidepressant effect is thought to be hyperforin, other constituents such as hypericin, pseudohypericin, flavonoids and oligomeric procyanidines may also play a direct or indirect role. While reuptake inhibition may more than likely be responsible for most of the antidepressant effect, other mechanisms may also contribute alone or in combination to exert the overall antidepressant action.

The acute effects of an extract of Bacopa monniera (Brahmi) on cognitive function in healthy normal subjects.

The Ayurvedic medicine Bacopa monniera (Brahmi) has been shown to exert cognitive enhancing effects in animals. The current study examined the acute effects of an extract of Bacopa monniera on cognitive function in normal healthy human subjects. The study was a double-blind, placebo-controlled independent group design in which subjects were randomly allocated to one of two treatment conditions, Bacopa monniera (300 mg) (n = 18) or placebo (n = 20). Neuropsychological testing was conducted before and 2 h after drug administration. No significant changes were found on any of the tests. The findings suggest that Bacopa monniera, at least for the dose administered, has no acute effects on cognitive functioning in normal healthy subjects. Copyright 2001 John Wiley & Sons, Ltd.

A preliminary investigation on the acute pharmacodynamic effects of hypericum on cognitive and psychomotor performance.

Research has indicated that the herb St John's Wort (Hypericum perforatum) has comparable efficacy to conventional antidepressants in the treatment of depression. Although clinical studies have demonstrated that hypericum has a superior side-effect profile compared to standard antidepressants, no study has directly compared the cognitive and psychomotor effects of hypericum with those of other antidepressants. The aim of the current study was to examine the acute effects of hypericum on cognitive and psychomotor function, and to compare its effects with those of amitriptyline. Thirteen healthy volunteers received an acute dose of placebo, amitriptyline (25 mg, positive control) or hypericum (900 mg or 1800 mg) in a double-blind, placebo-controlled design. Cognitive and psychomotor tests and subjective measures of sedation were administered before and 1, 2 and 4 hours after drug administration. Amitriptyline impaired performance on a battery of psychological tests, which included critical flicker fusion (CFF), choice reaction time (CRT), digit symbol substitution test (DSST), profile of mood states (POMS) and the line analogue rating scale (LARS), while hypericum had neutral effects on performance in these tests. However, hypericum induced a dose-related impairment on DSST. Current findings suggest that clinical doses of hypericum do not impair attention, sensorimotor function or information processing.

Isolation of 6-O-(p-coumaroyl)-catalpol from Tabebuia rosea.

From the bark of Tabebuia rosea, the iridoid 6-O-(p-coumaroyl)-catalpol (specioside) was isolated. Antimalarial properties have been attributed to the infusion prepared from this part of the plant, although the compound failed to exhibit antimicrobial activity. The structure was corroborated by comparison with reported data for specioside as well as some additional chemical and spectroscopic data described herein.