The cognitive effects of acute administration of herbal remedies to healthy volunteers
A number of Oriental and European herbal remedies have been historically attributed with cognition enhancing properties. They also exhibit physiological effects that may be commensurate with the enhancement of cognitive performance. This thesis examined the cognitive and mood effects of acute administration of Gingko biloba, Panax ginseng, a combination of ginkgo/ginseng, S. lavandulaefolia (Sage) and Melissa officinalis (Lemon balm) to healthy volunteers, in a series of double-blind, placebo-controlled, balanced cross-over, multiple-dose, multiple time-point experiments. In the case of each herbal remedy, treatment related changes in cognitive performance were quantified with computerised assessment tools (the CDR battery and serial subtraction tasks), and mood was assessed with Bond-Lader visual analogue scales. Relevant in vitro properties of both sage and lemon balm were also assessed. In separate studies electroencephalograph (EEG) recordings following both Ginkgo biloba and Panax ginseng, and blood glucose levels obtained following the latter of these, were also analysed. The results show that all of the herbal remedies under investigation are capable of modulating cognitive performance, mood, and, where they have been assessed, physiological parameters. The most striking results include: improved speed of attentional tasks following ginkgo; improved serial subtraction performance following both ginkgo and the ginkgo/ginseng combination; consistently improved secondary memory performance following ginseng and the ginkgo/ginseng combination, but with decrements in the speed of performing attentional tasks for the less optimum doses of each; modulation of EEG recordings following both ginkgo and ginseng; improved memory performance and mood following sage; and decrements on timed memory tasks for lemon balm, but with differential modulation of mood and improved accuracy of memory task performance depending on the dose and cholinergic properties of the specific treatment. The majority of these studies represent either the first studies to investigate cognitive modulation in humans, or alternatively the first studies to investigate the cognitive effects of single doses in humans, of each of the treatments under investigation.