 The aim of the study is to evaluate the effect of EGb761, in comparison to placebo, on cerebral glucose metabolism, in three groups of elderly patients: newly diagnosed mild Alzheimers disease AD, memory complaint patients with cognitive impairment MC and memory complaint patients cognitively normal CNE. The first phase includes four weeks treatment with EGb761 for all groups, with change in brain glucose metabolism at month 1 using 18 FDG-PET, as primary endpoint which will be followed by an open 17 months follow-up FU period with EGb761 treatment in MC and CNE patients. 