Neural stem cells proliferate in the subventricular zone and hippocampal dentate gyrus of adult mammals. However, the number of endogenous neural stem cells is insufficient to prevent cerebral ischemia/reperfusion injuries such as vascular dementia, so it is important to stimulate endogenous neural stem cell proliferation and differentiation. The ginkgo biloba extract EGb761 effectively and safely treats memory loss and cognitive impairments in patients with senile dementia. 

Thanks for posting, Myriam.  Very interesting. 

If I understand right, the clinical trials using ginkgo for memory have been mixed.  But on the positive side, ginkgo is the only supplement that WebMD rates as "possibly effective" for "memory impairment."

http://www.webmd.com/vitamins-supplements/condition-1746-Memory+impairment.aspx?diseaseid=1746&diseasename=Memory+impairment&source=2

WebMD also considers ginkgo to be one of the supplements "possibly effective" for Alzheimer's:

http://www.webmd.com/vitamins-supplements/condition-981-Alzheimer%27s+disease.aspx?diseaseid=981&diseasename=Alzheimer%27s+disease&source=2

And according to a press release, this EGb761 (the specific ginkgo used in the study you cited) is readily available over-the-counter in the U.S.:

"In the U.S., EGb761 is sold under the Ginkgold brand name and
distributed to natural product stores by Nature's Way Products, Inc..."

http://www.prnewswire.com/news-releases/us-study-proves-efficacy-of-patented-ginkgo-extract-for-alzheimersdementia-within-26-weeks-72596862.html