First-Episode Schizophrenic Psychosis Differs From First-Episode Affective Psychosis and Controls in P300 Amplitude Over Left Temporal Lobe

Abstract

Left-sided P300 abnormality in first-episode schizophrenia relative to first-episode affective psychosis and controls suggests that P300 asymmetry is specific to schizophrenic psychosis and present at initial hospitalization. This P300 asymmetry suggests left temporal lobe dysfunction at the onset of schizophrenia.

P300 asymmetry and positive symptom severity: A study in the early stage of a first episode of psychosis

“…The substantial reduction in midline P300 amplitude in FEP-S patients relative to normal controls confirms previous findings (e.g., Salisbury et al 1998;McCarley et al 2002). However, this reduction appears to be of greater magnitude in the present study: P300 peak amplitudes in FEP-S patients were about half of that found by Salisbury et al (1998), and one third of that found by McCarley et al (2002).…”

“…However, this reduction appears to be of greater magnitude in the present study: P300 peak amplitudes in FEP-S patients were about half of that found by Salisbury et al (1998), and one third of that found by McCarley et al (2002). In addition to the differences between the experimental protocols used, a possible explanation for this discrepancy is medication.…”

“…For the study of P300 amplitude, one ANOVA was run with anterior-posterior site (Fz vs. Cz vs. Pz) as within subject factor to investigate midline P300 amplitude, and the other ANOVA with laterality (T3 vs. T4) to investigate P300 asymmetry. To avoid confounding effects that could be generated by global between group differences as to their P300 amplitudes, all lateral analyses were conducted on normalized mean amplitudes, that is by dividing amplitudes at T3 and at T4 by the mean amplitude observed at Cz, as in Salisbury et al (1998).…”

“…The amplitude of the P300 event-related potential (ERP) is consistently reduced over midline electrodes, not only in schizophrenia patients (reviewed in Ford, 1999), their relatives (Bharath et al, 2000), subjects at high risk for schizophrenia (van der Stelt et al, 2005) and patients having suffered from a first-episode of schizophrenia (Hirayasu et al, 1998;Salisbury et al, 1998;Brown et al, 2002;McCarley et al, 2002) but also in patients with an affective psychosis (Salisbury et al, 1999;O'Donnell et al, 2004) and in several other diseases compared to normal controls (Ford, 1999).…”

“…As to studies of patients having suffered from a first-episode of psychosis (FEP), two did report a greater reduction of P300 over the left than the right temporal lobe (Salisbury et al, 1998;McCarley et al, 2002), whereas others, like Hirayasu et al (1998), did not describe this asymmetry. Interestingly, the mean age of the patients of the latter study was close to that of the younger patients of Iwanami et al (2002), whereas, in the two FEP studies that reported P300 asymmetry (Salisbury et al, 1998;McCarley et al, 2002), mean age was clearly greater. Thus, it is possible that the asymmetry develops, or is detectable, only after having experienced symptoms of schizophrenia for a relatively longer period of time.…”