Impaired cognitive function in schizophrenia, once thought to be a sec
ondary effect of the psychosis, is now seen as an enduring and core fe
ature. It has many manifestations, but the most disruptive element is
arguably a fundamental defect in the patient's ability to manipulate a
vailable information. The magnitude of the cognitive deficit in schizo
phrenia is considerable and remains relatively stable despite fluctuat
ions in other symptoms. The degree of dysfunction also has a high pred
ictive value for long-term disability. In recent years, more attention
has been directed towards cognitive dysfunction in schizophrenia as a
result of which assessment scales and diagnostic systems increasingly
incorporate cognitive dysfunction as an independent domain. Good cogn
itive function depends upon the brain's ability to prioritize tasks an
d to switch from parallel processing to sequential processing when the
processing load is excessive. This requires working executive memory.
Neuroimaging and functional analyses suggest that such cognitive func
tion relies upon unimpaired prefrontal activity. In addition, there is
increasing evidence that antipsychotic drugs with 5-hydroxytryptamine
(5-HT)(2A)-blocking activity produce better cognitive function in pat
ients with schizophrenia than drugs with predominantly dopamine (D)(2)
-blocking activity (conventional neuroleptics). The development of sop
histicated, computer-delivered maze tasks has shown that newer antipsy
chotics, such as clozapine and risperidone, differ from conventional n
euroleptics in their effects on cognitive function. The prospects, the
refore, are that patients treated with drugs having 5-HT2A-blocking ac
tivity will have better cognitive function and will be better able to
function in life's roles than will patients treated with conventional
neuroleptics.