Effects of Ginkgo biloba extract EGb 761® on cognitive control functions, mental activity of the prefrontal cortex and stress reactivity in elderly adults with subjective memory impairment – a randomized double‐blind placebo‐controlled trial

OBJECTIVE: Cognitive control as well as stress reactivity is assumed to depend on prefrontal dopamine and decline with age. Because Ginkgo biloba extract EGb761® increases prefrontal dopamine in animals, we assessed its effects on cognitive functions related to prefrontal dopamine. METHODS: Effects of 240‐mg EGb761® daily on task‐set‐switching, response‐inhibition, delayed response, prospective‐memory, task‐related fMRI‐BOLD‐signals and the Trier Social Stress‐Test were explored in a randomized, placebo‐controlled, double‐blind pilot‐trial in 61 elderly volunteers with subjective memory impairment. RESULTS: Baseline‐fMRI‐data showed BOLD‐responses in regions commonly activated by the specific tasks. Task‐switch‐costs decreased with EGb761® compared to placebo (ANOVA‐interaction: Group × Time × Switch‐Costs p = 0.018, multiple tests uncorrected), indicating improved cognitive flexibility. Go–NoGo‐task reaction‐times corrected for error‐rates indicated a trend for improved response inhibition. No treatment effects were found for the delayed response and prospective‐memory tasks and fMRI‐data. A non‐significant trend indicated a potentially accelerated endocrine stress‐recovery. EGb761® was safe and well tolerated. CONCLUSION: We observed indications for improved cognitive flexibility without changes in brain activation, suggesting increased processing efficiency with EGb761®. Together with a trend for improved response inhibition results are compatible with mild enhancement of prefrontal dopamine. These conclusions on potential beneficial effect of EGb761® on prefrontal dopaminergic functions should be confirmed by direct measurements. © 2016 The Authors. Human Psychopharmacology: Clinical and Experimental published by John Wiley & Sons, Ltd.