The present invention relates to compounds 3-amino-1-hydroxy-2-oxo-1,2,3, 4-tetrahydroquinoline-7-carbonitrile, 3-amino-1-hydroxy-7-(2-methoxyethoxy)-3,4-dihydroquinolin-2(1H)-one, and 3-amino-1-hydroxy-7-[(1S)-2-methoxy-1-methylethoxy]-3,4-dihydroquinolin-2(1H)-one, including racemic mixtures and resolved enantiomers thereof, to pharmaceutically acceptable salts thereof, and to the treatment of cognitive deficits associated with schizophrenia and other psychiatric, neurodegenerative and/or neurological disorders in mammals, including humans.