Event-related potentials during a selective attention task with short interstimulus intervals in patients with schizophrenia.

OBJECTIVE

To study selective attention in schizophrenia by examining event-related potentials during a dichotic listening task with short interstimulus intervals (ISIs).

DESIGN

Prospective study.

PARTICIPANTS

Twelve patients with schizophrenia in remission and 12 age-matched controls with no history of psychiatric or neurological illness.

INTERVENTIONS

Participants were asked to push a button in response to target stimuli in either ear.

OUTCOME MEASURES

Reaction time, correct response rate and results of electroencephalography recorded at 3 regions: mean segmental amplitudes between 0 and 200 ms and between 200 and 400 ms after stimuli and processing negativity (Nd), measured by the negative area during these periods.

RESULTS

Distinct slow-positive potentials for unattended stimuli, which were elicited in a task with long ISIs in a previous report, did not emerge in either group in this study. Although the 2 groups did not differ significantly in terms of Nd area, in the controls the mean segmental amplitude for attended standard stimuli was significantly greater than that in the patients with schizophrenia.

CONCLUSIONS

Impairment of selective attention in patients with schizophrenia is related to a lack of ability to focus attention on attended task-relevant stimuli during a selective attention task with short ISI.