P300 as an index of transition to psychosis and of remission: Data from a clinical high risk for psychosis study and review of literature

Abstract

Auditory P300 oddball and novel components index working memory operations and salience processing, respectively, and are regarded as biomarkers of neurocognitive changes in both chronic and first-episode schizophrenia. Much less is known about whether P300 abnormalities exist in individuals at clinical high risk for psychosis (CHR) and if they are predictors of both transition to psychosis and remission from symptoms. One hundred and four CHR and 69 healthy control individuals (HC) completed P300 oddball paradigm, and 131 CHR and 69 HC subjects completed P300 novel paradigm. All CHR subjects were followed up for one year and stratified into CHR converters (CHRC) and non-converters (CHR-NC), with CHR-NC further stratified into remitted and non-remitted subgroups. Between-group comparisons of P300 oddball and novel amplitude and latency were performed among CHRC, CHR-NC and HC, as well as among CHRC, non-remitted CHR, remitted CHR and HC. CHR converters had lower fronto-central P300 novel amplitude as well as marginally lower P300 oddball amplitude relative to HC. When CHR non-converters were stratified into remitted and non-remitted subgroups, P300 novel amplitude in remitted CHR subjects was comparable to HC, and it was higher than that in CHR subjects who converted to psychosis or who did not remit. Thus, reduced P300 novel amplitude indexing impaired salience processing marked both conversion to psychosis and remission from psychotic symptoms.

Keywords: Clinical high risk for psychosis; P300 novel; P300 oddball; Remission from psychotic symptoms; Transition to psychosis.

Figure 1.

Grand average ERPs at baseline to target stimuli in the P300 oddball paradigm (a) and to novel stimuli in the P300 novel paradigm (b). CHR-C, subjects at clinical high risk for psychosis who converted into psychosis; CHR-NC, CHR subjects who did not convert into psychosis; HC, healthy controls.

Figure 2.

Group differences in the P300 novel and oddball amplitudes. (a) CHR converters and non-remitted CHR subjects had lower P300 novel amplitudes at fronto-central electrodes (e.g. FCz) than remitted CHR subjects and HC. (b) Few group differences were observed in the P300 oddball amplitude.

Figure 3.

Significant correlations of the P300 oddball latency and scores of the speed of processing, attention/vigilance and working memory in CHR non-converters (CHR-NC) rather than CHR converters (CHR-C) and HC.