Reduced attention-related negative potentials in methamphetamine psychosis.

Auditory event-related potentials were recorded during a dichotic syllable discrimination task in 16 unmedicated patients who were in the residual state following the remission of acute methamphetamine (MAP) psychosis, and in 16 age-matched normal controls. The subjects were instructed to press a button in response to the target syllables applied to one designated ear. In the patients with MAP psychosis, the area of attention-related negative potentials was significantly smaller than that in the normal controls. The two groups did not differ significantly in P300 amplitude or latency. These results suggest that patients with MAP psychosis show impairment of selective attention, although they have less cognitive deficit than schizophrenic patients.