The effect of neuroleptics on cognitive and psychomotor function.

There has been great variability and inconsistency in the reported effects of neuroleptic drugs on cognitive and psychomotor function in both patients and normal controls. Experimental design rather than any particular cognitive or psychomotor test appears to have determined the sensitivity of detection of neuroleptic drug effects. In general, sedative phenothiazines have been found to depress psychomotor function and sustained attention, but higher cognitive functions are relatively unaffected. In the majority of studies of schizophrenic patients, both cognitive function and attention improve with neuroleptic treatment, in parallel with clinical recovery. Negative symptoms are not increased and usually show slight improvement with neuroleptic treatment. Controls are more sensitive than schizophrenic patients to neuroleptic drug-induced impairments. Tolerance has been seen in patients but has not been demonstrated in normal volunteers. The way in which neuroleptics produce their beneficial effects in patients remains unknown. Three main hypotheses to replace early arousal theories are proposed: normalisation of attention, facilitated indirectly by suppression of 'released' limbic dopamine hyperactivity; normalisation of asymmetrical temporohippocampal function; or direct improvement of attentional processing. Studies of the effects of new antipsychotic drugs with selective actions and the development of more reliable and selective tests of psychomotor and cognitive functions are required.