Use of neuroimaging techniques in the assessment of nutraceuticals for cognitive enhancement: Methodological and interpretative issues

The following review provides a comparison of neuroimaging techniques (electrophysiology [EEG], steady-state topography [SST], near-infrared spectroscopy [NIRS], functional magnetic resonance imaging [fMRI] and positron-emission tomography [PET]) which have been used to study nutraceutical interventions for cognition in healthy adults. Recent research in the area is summarised for the following substances: glucose, green tea extracts, caffeine, theanine, chlorogenic acid, Panax ginseng, nicotine, Ginkgo biloba, multivitamins, fish oils, soybean peptide, resveratrol, creatine, guaraná and cocoa flavanols. A brief outline of the individual neuroimaging techniques, together with methodological and interpretative issues associated with each of these technologies, is presented. A review of acute and chronic neurocognitive intervention studies featuring nutraceutical substances over the past 20 years is also presented for each of these neuroimaging modalities. Following this, a general discussion of common pitfalls associated with neuroimaging and psychopharmacology is also included, including the importance of directional hypothesis testing, the careful selection of difficulty level when specifying a cognitive activation task and how to correct for multiple comparisons whilst maintaining an acceptable level of statistical power. Recommendations for future research using neuroimaging in conjunction with nutraceutical interventions are outlined.