Over recent years there has been increasing interest in the area of cognitive enhancement. This field has traditionally focused on the effects of so-called nootropics in those with fragile cognition (e.g. those with age-related cognitive decline, mild cognitive impairment or dementia). However in recent years the field of cognition enhancement has also embraced studies into cognition enhancement in young, cognitively intact individuals . In the context of pharmaceutical cognition enhancers, methylphenidate and modafinil (Provigil) have taken centre stage . Modafinil had been taken as a cognitive enhancer by around 10% of respondents to an online survey of the readership of the journal Nature , though it is worth noting that this study may have a high response bias from individuals using cognitive enhancers.
As well as pharmaceutical approaches to cognitive enhancement, there is growing interest in the possibility that certain nutraceuticals may enhance cognitive performance. Herbal extracts may contain multiple active components which, in concert, may influence numerous neuronal, metabolic and hormonal systems involved in behavioural processes . Additionally the interactions between these actives may be synergistic, resulting in complex dose and time dependent effects. These factors are challenging for psychopharmacology, making certain positive effects fragile even where there is strict batch to batch consistency across studies, and rendering negative findings sometimes difficult to interpret. Nevertheless there is growing evidence that certain standardized natural products have reproducible neurocognitive effects in humans, possibly because of their inherent polyphamacological properties. Examples of the most promising nutraceuticals in this context include species of Salvia (sage) [5-8], Panax ginseng [9-12] and Bacopa monniera [13-17]. For the purposes of this short review we chose to concentrate on Ginseng and Bacopa. The former has been shown to enhance robustly cognitive performance after acute dosing , whilst Bacopa has been shown to have nootropic effects with chronic dosing .
We are not aware of any study to date which has directly compared the cognition enhancing effects of a nutraceuticals and a pharmaceutical in a head to head trial in healthy volunteers. The purpose of this review is to examine the literature describing clinical trials of the neurocognitive effects of modafinil, Panax ginseng and Bacopa monniera in order to compare their effect sizes across different cognitive domains.