Agents potentiating nerve growth factor activity are provided for treating Alzheimer's disease which contain as the active ingredient dodecatrienoic acid derivatives represented by the general formula (I): 1 wherein X represents hydrogen, CHO, COOH, COOR (wherein R represents an ester residue or an addition salt comprising an alkali metal salt or an organic acid salt group), provided that in case where X is COOH, it is bonded to the carbon atom at the position marked with * so as to form a lactam O.dbd.C--O--.