A pharmaceutical composition for use in the treatment or prevention of cerebral acetylcholine neuron dysfunction in the sequelae of cerebrovascular dementia, senile dementia, Alzheimer's disease, ischemic brain injury and cerebral apoplexy or memory impairment caused by neuronal death selective, comprising the following ingredients (A) and (B): Ingredient (A) an alkyl ether derivative represented by the following formula: in which (R1 is a benzothienyl or benzofuranyl group which may be substituted with a group selected from halogen atom, alkyl group optionally substituted with a hydroxyl group, alkoxy group, carboxyl group, aminocarbonyl group, hydroxyl group, alkylthio group, phenyl group and pyridyl group； R2 represents a hydrogen atom； R3 is an alkyl group that may be substituted with a group selected from phenyl group optionally substituted with a hal atom Oxygen, alkoxy group or nitro group, optionally protected hydroxyl group, alkylamino group and alkynyl group； R4 is an alkyl group that may be substituted with a phenyl group； m is 1； and n represents an integer of 2 or 3；) or (R1 is a benzothienyl or benzofuranyl group which may be substituted with a group selected from halogen atom, alkyl group or phenyl group； R2 represents a hydrogen atom； R3 or R4 is an alkyl group that may be substituted with a hydroxyl group, optionally protected amino group and an alkylamino group； or R3 and R4 represents an azetidine ring, a pyrrolidine ring, a piperidine ring, a piperazine ring or a morpholine ring that it is formed by R3 and R4 together with the nitrogen atom to which R3 and R4 are attached, said ring being able to be substituted with at least one group chosen from halogen atom, optionally protected hydroxyl group, protected carboxyl group of optionally, optionally protected amino group, straight or branched chain C1-6 alkyl group, straight or branched chain C1-6 alkoxy group, C1-6 acyl group, cycloalkyl group, alkyl group C1-6-ar； m is 1； and n represents an integ
