A 5-HT 6 receptor antagonist for use in a method of treating Down syndrome, wherein the 5-HT 6 receptor antagonist is an effective amount of a compound having a structure according to Formula II: wherein: R z is selected from -H, -OH, -O(alkyl), -O(aryl) -O-S-phenyl, -O-S(=O)-phenyl, -O-S(=O) 2 -phenyl, -O-S-alkyl, -O-S(=O)-alkyl, -O-S(=O) 2 -alkyl, -O-S-haloalkyl, -O-S(=O)-haloalkyl, -O-S(=O) 2 -haloalkyl, -O-S-2,6-dihalophenyl, -O-S(=O)-2,6-dihalophenyl, or -OS(=0) 2 -2,6-dihalophenyl; R Y is selected from -H, -halogen, -NH 2, -NH(alkyl), -N(alkyl) 2, -NH(aryl), -N(aryl) 2, - N(aryl)(alkyl), -N-heterocycle, or -N-heterocycloalkyl, where, in the case of - N(alkyl) 2 or -N(aryl) 2, the alkyl groups or the aryl groups can be identical or different; R w is selected from -H, -OH, -O(alkyl), -O(aryl), -halogen, -alkyl, or haloalkyl; R v is selected from -H, -2-ethyl-NH(alkyl), -2-ethyl-N(alkyl) 2, -2-ethyl-NH(aryl), -2-ethyl-NH(arylalkyl), -2-ethyl-NH(benzyl), -2-ethyl-NH(alkoxybenzyl), -2-ethyl-NH(haloalkoxybenzyl), -2-ethyl-NH(m-haloalkoxybenzyl), -2-ethyl-N(aryl) 2, -2-ethyl-N(alkyl)(aryl), -3-propyl-NH(alkyl), -3-propyl-N(alkyl) 2, -3-propyl-NH(aryl), -3-propyl-N(aryl) 2, -3-propyl-N(aryl)(alkyl), -N-heterocycle, or -N-heterocycloalkyl, where, in the case of a dialkyl or diaryl nitrogen, the alkyl groups or the aryl groups can be identical or different; Z' is selected from -H, -CH 2 - -CHX-, -CX 2 - -CH(alkyl)-, -CH(aryl)-, -C(aryl)(alkyl)-, - C(alkyl) 2 -, -C(aryl) 2 - -O-, -S-, -S(=O)-, or -S(=O) 2 - where X is a halogen and where, in the case of -C(alkyl) 2 - or -C(aryl) 2 -, the alkyl groups or the aryl groups can be identical or different; and R x is optionally present, and if present is selected from -H, -OH, -O(alkyl), -O(aryl), - halogen, -alkyl, -haloalkyl, or -aryl; and pharmaceutically acceptable hydrates, solvates, tautomers, and salts thereof. R z is selected from -H, -OH, -O(alkyl), -O(aryl) -O-S-phenyl, -O-S(=O)-phenyl, -O-S(=O) 2 -phenyl, -O-S-alkyl, -O-S(=O)-alkyl, -O-S(=O) 2 -alkyl, -O-S-haloalkyl, -O-S(=O)-haloalkyl, -O-S(=O) 2 -haloalkyl, -O-S-2,6-dihalophenyl, -O-S(=O)-2,6-dihalophenyl, or -OS(=0) 2 -2,6-dihalophenyl; R Y is selected from -H, -halogen, -NH 2, -NH(alkyl), -N(alkyl) 2, -NH(aryl), -N(aryl) 2, - N(aryl)(alkyl), -N-heterocycle, or -N-heterocycloalkyl, where, in the case of - N(alkyl) 2 or -N(aryl) 2, the alkyl groups or the aryl groups can be identical or different; R w is selected from -H, -OH, -O(alkyl), -O(aryl), -halogen, -alkyl, or haloalkyl; R v is selected from -H, -2-ethyl-NH(alkyl), -2-ethyl-N(alkyl) 2, -2-ethyl-NH(aryl), -2-ethyl-NH(arylalkyl), -2-ethyl-NH(benzyl), -2-ethyl-NH(alkoxybenzyl), -2-ethyl-NH(haloalkoxybenzyl), -2-ethyl-NH(m-haloalkoxybenzyl), -2-ethyl-N(aryl) 2, -2-ethyl-N(alkyl)(aryl), -3-propyl-NH(alkyl), -3-propyl-N(alkyl) 2, -3-propyl-NH(aryl), -3-propyl-N(aryl) 2, -3-propyl-N(aryl)(alkyl), -N-heterocycle, or -N-heterocycloalkyl, where, in the case of a dialkyl or diaryl nitrogen, the alkyl groups or the aryl groups can be identical or different; Z' is selected from -H, -CH 2 - -CHX-, -CX 2 - -CH(alkyl)-, -CH(aryl)-, -C(aryl)(alkyl)-, - C(alkyl) 2 -, -C(aryl) 2 - -O-, -S-, -S(=O)-, or -S(=O) 2 - where X is a halogen and where, in the case of -C(alkyl) 2 - or -C(aryl) 2 -, the alkyl groups or the aryl groups can be identical or different; and R x is optionally present, and if present is selected from -H, -OH, -O(alkyl), -O(aryl), - halogen, -alkyl, -haloalkyl, or -aryl;