An alkyl ether derivative represented by theformula:(see formula 1)wherein R1, R2, R3, R4, m and n are as defined in thespecification, or salts thereof exhibitssynergistically improved anti-hypoxic activity whencombined with a compound having an acetylcholineesterase inhibitory activity. Therefore, thecombination according to the present invention isuseful as a method for improving cerebral function.Further, a pharmaceutical composition containing thecompound relating to the combination according to thepresent invention is useful for treatment andprevention of dysfunction of cerebral acetylcholineneurons in the sequelae of cerebrovascular dementia,senile dementia, Alzheimer's disease and ischemiccerebral lesion and in the cerebral apoplexy or thememory impairment caused by selective neuronal death.
