Abstract: A use of the pyrrolidone derivative represented by the following formula [I] as an anti-amnesitc agent: ##STR1## wherein R represents a group ##STR2## X represents --SO.sub.2 -- or --CO--; R' represents a hydrogen atom, a lower alkyl group, a trifluoromethyl group, a halogen atom or a nitro group; n denotes an integer of 1-5; and, when n is an integer of 2 or more, R' may be the same or different, provided that(a) when X is --SO.sub.2 --, there is no case where R' is 3-CF.sub.3, 4-Cl-5-CF.sub.3, 3,5-(CF.sub.3).sub.2 or 3-NO.sub.2 ;(b) when X is --CO--, there is no case where n denotes 1 or 2 and R' is a halogen atom or a nitro group;(c) when X is --SO.sub.2 --, there is no case where n denotes 1 or 2 and R' is a group other than 4-Cl or 3-NO.sub.2 ; and(d) when n denotes 2, there is no case where the groups R' represent the same group which is halogen atom or a nitro group.