The present invention relates to heterocyclic compound as cognitive enhancers. The heterocyclic compound may be represented by the formula I: (see formula I) wherein (see formula II) represents (see formula III), (see formula IV), (see formula V), (see formula VI), (see formula VII), (see formula VIII) or (see formula IX). In formula 1, R1 represents hydrogen atom, C1-C6 alkyl or benzyloxy; R2 represents methyl or nil; R3 represents hydrogen atom, C1-C6 alkyl, C2-C6 alkenyl, C3-C8 cycloalkyl or -CH2R5, wherein R5 represents thienyl or phenyl which may be substituted with C1-C6 alkyl, halogen atom or cyano; R4 represents C1-C6 alkyl, C2-C6 alkenyl, C3-C8 cycloalkyl or -CH2R6, wherein R6 represents naphthyl, thienyl or phenyl, which may be substituted with C1-C6 alkyl, halogen atom or cyano; or R3 is coupled with R4 into (see formula X), (see formula XI), (see formula XII) wherein R7 represents hydrogen atom, halogen atom, C1-C6 alkoxy, cyano or trifluoromethyl, (see formula XIII), cyclopentene or cyclopentane, provided that, when (see formula XIV) represents (see formula XV), R3 is a hydrogen atom or is coupled with R4 into (see formula XVI), (see formula XVII), (see formula XVIII) wherein R8 represents halogen atom, C1-C6 alkoxy, cyano or trifluoromethyl, (see formula XIX), cyclopentene or cyclopentane, where * is a point of attachment to formula (I).
HETEROCYCLIC COMPOUNDS AND COGNITIVE ENHANCERS COMPRISING THE SAME AS EFFECTIVE COMPONENTS