Trial-by-trial ERP-behavior relationships in psychosis: Between- and within-person variability in performance monitoring adjustments

Cognitive impairment in schizophrenia, characterized by deficits in performance monitoring, predicts clinical and functional outcomes. The error-related negativity (ERN), a neurophysiological index of error detection, is reduced in psychosis, but it is unclear why this impaired error detection is not closely linked to behavioral adjustments. A possibility is that research has overrelied on examining between-person relationships of average ERN and behavior, rather than focusing on within-person, trial-by-trial changes. This study aimed to determine whether neurophysiological indices of error detection (ERN, error positivity [Pe]) predict within-person post-error behavioral adjustments in psychotic disorders and whether these relationships are weaker in people with psychosis than in controls. ERN and Pe were assessed during a flanker task in 72 participants with psychosis (PwP) and 82 healthy comparison participants. Multilevel location-scale models examined trial-by-trial changes in the relationships between event-related potentials (ERPs) and behavior (response [RTs], accuracy). Results showed that ERP-RT relationships were similar across PwP and controls. In both groups, greater within-person increases in ERN predicted longer and more variable RTs following correct trials. Larger within-person increases in Pe predicted shorter and more variable RTs following correct trials, but less variable RTs following error trials. Exploratory analyses in a subset of participants with schizophrenia showed similar effects. ERP-accuracy relationships were neither observed nor moderated by diagnostic group. Within-person ERP-behavior relationships were preserved in psychosis, indicating intact performance monitoring at the individual level. This supports performance monitoring as a transdiagnostic construct and underscores the importance of examining intraindividual variability to understand performance monitoring in psychotic disorders.