A reduction in the error-related negativity (ERN), a response-locked event-related potential (ERP) observed when participants commit errors during processing of stimuli, is a well-replicated cerebral abnormality in schizophrenia. However, the extent to which this abnormality reflects susceptibility to schizophrenia rather than overt change in behavioural state is unclear. As the unaffected siblings of individuals with schizophrenia are at an increased genetic risk, this study examines whether they display abnormality of the ERN similar to that observed in individuals with schizophrenia. ERPs were recorded from 29 individuals with schizophrenia, 36 unaffected siblings and 35 healthy control participants while they performed a simple Go/No-Go task. Group differences in the ERN and also in the error positivity (Pe), a response-locked positive component that follows the ERN, were investigated. Reductions of ERN amplitudes were found in both individuals with schizophrenia and siblings. No significant abnormalities were observed in Pe. The finding of reduced ERN amplitudes in siblings without prodromal symptoms supports the hypothesis that the abnormality is not a consequence of behavioural disturbance, and that it is a trait marker for susceptibility to schizophrenia, rather than being a result of illness or medication.
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