Neurophysiological effects of Rhodiola rosea extract containing capsules (A double-blind, randomised, placebo-controlled study)

In 1947 Dr. Nicolai Lazarev introduced the term “adaptogen” in order to define special plant-derived extracts like Ginseng, which seemed to help to cope with stress-induced physical and psychic weakness. Extracts from Rhodiola rosea L. were recognized to belong to this category of food supplements. Due to contradictory results in the literature it was decided to examine the neurophysiological effect of Rhodiola rosea extract on surrogate parameters of cognitive and emotional brain processing in 20 volunteers. Spectral signatures of regional electric brain activity were recorded under control of an Eye-Tracking device, by means of which different challenges were presented. Among the cognitive challenges was a Stroop test, a memory test and a picture comparison for search of small deviations; among the emotional challenges were three pictures:a crying child, a bird spider and a picture taken from the TV series “Jungle Camp”. Additionally, three film excerpts were shown: a boring and an exciting animal film as well as a horror trailer. Evaluation of all challenges against looking at a fixation cross on the screen revealed highly statistically significant differences. These consisted (among others) in considerable higher spectral power values of delta and theta power in frontal and occipital brain areas during all cognitive and emotional tasks except for the crying child and bird spider, where only occipital power increased. Exactly these parameters changed in the presence of Rhodiola rosea extract, where increases of delta and theta power in these regions were documented in comparison to placebo. These statistically significant increases indicate mental activation according to literature. Likewise, an increase of alpha2 spectral power was observed during performance of the memory test indicating activation of memory processes as known from literature. In summary, the extract from Rhodiola rosea modulated cognitive and emotional surrogate parameters indicating improvement of mental processing in a stimulatory and activating sense.