The method of this invention comprises administering to a patient suffering from or susceptible to schizophrenia or schizophreniform conditions an effective amount of a compound of formula (I), wherein X is oxygen or sulphur; G is selected from one of the following azabicyclic rings (a) or (b) wherein the thiadiazole or oxadiazole ring can be attached at any carbon atom of the azabicyclic ring.
