ACUTELY ADMINISTERED HALOPERIDOL HAS LITTLE EFFECT ON STEADY-STATE VISUAL EVOKED-POTENTIALS FROM PATTERN-REVERSAL STIMULATIONS IN TREATED SCHIZOPHRENICS

The amplitude changes in steady-state visual evoked potentials (VEPs) from pattern-reversal stimulations at 30 min after an intramuscular in jection of haloperidol were examined in 10 treated schizophrenics. The VEP amplitudes to hemi-field or full-field pattern-reversal stimulati ons with a standard check size were almost unchanged after the haloper idol injection as compared with those before the injection. However, w hile the VEP amplitudes to the full-field stimulations were significan tly higher in the midline occipital portion than in the right occipita l portion before the injection, no significant difference was observed after the injection. Further, the VEPs similarly responded to the cha nge in the check sizes used in the full-field stimulations before and after the injection, both showing significantly lower amplitudes only at the large check size of 4.1-degrees in a visual angle than that of 1.0-degrees. These results indicate that acutely administered haloperi dol has little effect on steady-state VEPs from pattern-reversal stimu lations in treated schizophrenics.