EGb-761, a standardized extract of Ginkgo biloba, is approved by German authorities as an effective treatment for primary degenerative dementia and vascular dementia. Tacrine® (tetrahydroaminoacrine) is the only drug approved in the U.S. for the treatment of Alzheimer's disease. An open, uncontrolled trial was conducted to compare the pharmacological activity of ginkgo and Tacrine in elderly patients with mild-to-moderate dementia. Results showed that both substances exhibit "cognitive activator" type effects, characterized by CEEG profiles demonstrating an increase of 7.5 to 13 cps activity and decreased slow frequencies. Ginkgo biloba (240 mg) exhibited "cognitive activator" profiles in more subjects than Tacrine (40 mg), and subjects who showed more cognitive-activator responses to the first dose of ginkgo also demonstrated better therapeutic effects with chronic administration of ginkgo.  

Itil T, Ahmed I, Le Bars P, et al. "The pharmacological effects of ginkgo biloba (GB), a plant extract, on the brain in comparison to Tacrine." Psychopharmacology Bulletin 1996;32(3):459.