This invention provides methods of improving cognitive function by administering to a subject a therapeutically effective amount of a fused heterocycle having the formula: ##STR00001## in which R.sup.1 is a member selected from the group consisting of H, substituted or unsubstituted arylalkyl and substituted or unsubstituted heteroarylalkyl. R.sup.2 is a member selected from the group consisting of H substituted or unsubstituted alkenyl, substituted or unsubstituted arylalkyl and substituted or unsubstituted heteroarylalkyl. R.sup.3 is a member selected from the group consisting of H, C.sub.1-C.sub.6 substituted or unsubstituted alkyl, substituted or unsubstituted arylalkyl and substituted or unsubstituted heteroarylalkyl. R.sup.4 is a member selected from OH and O.sup.-X.sup.+, in which X.sup.+ is positive ion which is a member selected from organic positive ions and inorganic positive ions. Substituted or unsubstituted arylalkyl and substituted or unsubstituted heteroarylalkyl moieties have the formula: ##STR00002## in which Ar is a member selected from the group consisting of substituted or unsubstituted aryl and substituted or unsubstituted heteroaryl. The index n is an integer from 1 to 4.