EFFECTS OF CLOZAPINE, FLUPHENAZINE, AND PLACEBO ON REACTION-TIME MEASURES OF ATTENTION AND SENSORY DOMINANCE IN SCHIZOPHRENIA

Two reaction time (RT) paradigms were used to study clozapine's effect s on sustained and selective attention compared to fluphenazine and pl acebo in 25 chronic schizophrenic patients. Sensory dominance was stud ied via simple and choice RTs to lights and tones, and on double-stimu lus trials in which the two stimuli were presented simultaneously. Alt hough 8 of the 25 patients could not perform the RT tasks when taking placebo, there were no effects of clozapine on simple or choice RT com pared to placebo or fluphenazine. Subjects on all 3 treatments showed visual dominance: faster RT to lights than to tones on choice and doub le-stimulus trials. However, clozapine reduced this by means of a sele ctive increase in RT to lights. Clozapine reduced failures to respond to the tone on double-stimulus trials. This was shown to be due to red uctions in hallucinations. Clozapine does not generally improve attent ion, but it may increase the ability of schizophrenic persons to proce ss nondominant or unattended stimuli possibly by increasing the effici ency of resource allocation. This may be partially mediated by a reduc tion in hallucinations.