A composition for use in the prophylactic and/or therapeutic treatment of dementia, which comprises a compound represented by the following general formula, a tautomer or stereoisomer of the compound, or a pharmaceutically acceptable salt thereof, or a crystal or solvate thereof as an active ingredient: (wherein, R 1 represents an alkyl group having 1 to 8 carbon atoms, an alkyl group having 1 to 8 carbon atoms and substituted with 1 to 3 halogen atoms, -OR 4, -CO 2 R 5, or -S n R 6, where R 4 represents hydrogen atom, or an alkyl group having 1 to 8 carbon atoms, aralkyl group (the aryl moiety has 6 to 10 carbon atoms, and the alkyl moiety has 1 to 4 carbon atoms), alkylcarbonyl group having 2 to 9 carbon atoms, arylcarbonyl group (the aryl moiety has 6 to 10 carbon atoms), aralkylcarbonyl group (the aryl moiety has 6 to 10 carbon atoms, and the alkylcarbonyl moiety has 2 to 5 carbon atoms), or aryl group having 6 to 10 carbon atoms, which may have a group or atom selected from a halogen atom, hydroxy group, nitro group, and cyano group as a substituent, R 5 and R 6 independently represent hydrogen atom, or an alkyl group having 1 to 8 carbon atoms, aralkyl group (the aryl moiety has 6 to 10 carbon atoms, and the alkyl moiety has 1 to 4 carbon atoms), or aryl group having 6 to 10 carbon atoms, which may have a group or atom selected from a halogen atom, hydroxy group, nitro group, cyano group, and amino group as a substituent, and n represents an integer of 0 to 2, R 2 represents hydrogen atom, a halogen atom, nitro group, cyano group, formyl group, an alkyl group having 1 to 8 carbon atoms, an alkyl group having 1 to 8 carbon atoms and substituted with 1 to 3 halogen atoms, or CO 2 R 7, where R 7 has the same meaning as that of R 5 mentioned above, R 3 represents hydrogen atom, a halogen atom, hydroxy group, amino group, CO 2 R 8, PO 3 H, PO (OR 9), S m R 10, or an alkyl group having 1 to 8 carbon atoms, or alkylaminocarbonyl group (the alkyl group has 1 to 8 carbon atoms), which may have a group or atom selected from a halogen atom, hydroxy group, nitro group, cyano group, and amino group as a substituent, where R 8, R 9, and R 10 have the same meaning as that of R 5 mentioned above, and m has the same meaning as that of n mentioned above, X represents NR 11, oxygen atom, or sulfur atom, where R 11 represents hydrogen atom, or an alkyl group having 1 to 8 carbon atoms, which may have a group or atom selected from a halogen atom, hydroxy group, nitro group, cyano group, and amino group as a substituent, and Y and Z represent nitrogen atoms. R 1 represents an alkyl group having 1 to 8 carbon atoms, an alkyl group having 1 to 8 carbon atoms and substituted with 1 to 3 halogen atoms, -OR 4, -CO 2 R 5, or -S n R 6, where R 4 represents hydrogen atom, or an alkyl group having 1 to 8 carbon atoms, aralkyl group (the aryl moiety has 6 to 10 carbon atoms, and the alkyl moiety has 1 to 4 carbon atoms), alkylcarbonyl group having 2 to 9 carbon atoms, arylcarbonyl group (the aryl moiety has 6 to 10 carbon atoms), aralkylcarbonyl group (the aryl moiety has 6 to 10 carbon atoms, and the alkylcarbonyl moiety has 2 to 5 carbon atoms), or aryl group having 6 to 10 carbon atoms, which may have a group or atom selected from a halogen atom, hydroxy group, nitro group, and cyano group as a substituent, R 5 and R 6 independently represent hydrogen atom, or an alkyl group having 1 to 8 carbon atoms, aralkyl group (the aryl moiety has 6 to 10 carbon atoms, and the alkyl moiety has 1 to 4 carbon atoms), or aryl group having 6 to 10 carbon atoms, which may have a group or atom selected from a halogen atom, hydroxy group, nitro group, cyano group, and amino group as a substituent, and n represents an integer of 0 to 2, R 2 represents hydrogen atom, a halogen atom, nitro group, cyano group, formyl group, an alkyl group having 1 to 8 carbon atoms, an alkyl group having 1 to 8 carbon atoms and substituted with 1 to 3 halogen atoms, or CO 2 R 7, where R 7 has the same meaning as that of R 5 mentioned above, R 3 represents hydrogen atom, a halogen atom, hydroxy group, amino group, CO 2 R 8, PO 3 H, PO (OR 9), S m R 10, or an alkyl group having 1 to 8 carbon atoms, or alkylaminocarbonyl group (the alkyl group has 1 to 8 carbon atoms), which may have a group or atom selected from a halogen atom, hydroxy group, nitro group, cyano group, and amino group as a substituent, where R 8, R 9, and R 10 have the same meaning as that of R 5 mentioned above, and m has the same meaning as that of n mentioned above, X represents NR 11, oxygen atom, or sulfur atom, where R 11 represents hydrogen atom, or an alkyl group having 1 to 8 carbon atoms, which may have a group or atom selected from a halogen atom, hydroxy group, nitro group, cyano group, and amino group as a substituent, and Y and Z represent nitrogen atoms.