Topographic abnormalities of P3 in schizotypal personality disorder.

Schizotypy, a schizophrenia spectrum disorder, is of interest because schizotypes share traits with schizophrenics, albeit milder, without potential confounds such as chronic neuroleptic treatment and/or hospitalization. Thus, schizotypy may be particularly useful in exploring biological correlates of an underlying schizophrenic predisposition. The P3 event-related potential, which is aberrant in schizophrenia, was measured in 11 male, right-handed, DSM-III-R-defined schizotypes and 11 matched controls while subjects covertly counted 1.5 kHz target tones (15%) in trains of 1 kHz standard tones. Like schizophrenics, schizotypes displayed an asymmetrical P3, with smaller amplitudes over the left temporal lobe. Unlike schizophrenics, schizotypes were not significantly smaller in P3 amplitude over the sagittal midline of the head, although there was a trend towards reduced amplitudes at central and posterior midline sites. Asymmetry of P3 amplitude, with left-sided deficit, may be associated with the schizophrenia diathesis, but overall P3 reductions may be more associated with chronic effects.