The invention relates generally to muscarinic agonists, which are useful for stimulating muscarine receptors, and treating cognitive disorders. Included among the muscarinic agonists disclosed herein are oxadiazole derivatives, compositions, and preparations thereof. Methods of synthesizing oxadiazole compounds also are provided. This disclosure also relates in part to compositions for enhancing cognitive function in subjects such as humans, the compositions comprising a muscarinic agonist or a pharmaceutically suitable form thereof. This disclosure relates in part to methods of treating animals such as humans by administering such compositions.