The invention relates to therapeutic uses of a 2-(diaza-bicyclo-alkyl)-pyrimidone derivative represented by formula (I): ##STR00001## Wherein R1, R2, R3, R4 and n are as defined herein. Specifically, the compounds of formula (I) are used for preventive and/or therapeutic treatment of a neurodegenerative disease caused by abnormal activity of GSK3.beta., such as Alzheimer's disease. The invention relates also to intermediates for the preparation of compound of formula (I).