N1 and P300 abnormalities in patients with schizophrenia epilepsy, and epilepsy with schizophrenialike features

Background: The scalp-recorded N1 and P300 components of the event-related brain potential (ERP) are commonly reduced in patients with schizophrenia b ut not in patients with epilepsy. Epilepsy patients with interictal chronic schizophrenialike features (EPI-SZ) provide a comparison group for determi ning whether the ERP amplitude abnormalities seen in schizophrenic patients nl E associated with shared clinical features of EPI-SZ and schizophrenic patients or overlapping pathophysiologies, or are specific to a distinct sc hizophrenia etiology. Methods: Patients with schizophrenia (n = 24) were compared with normal con trol subjects (n = 32) and patients with epilepsy syndromes on visual and a uditory oddball ERP paradigms. Epilepsy patients included those with chroni c interictal schizophrenialike features (n = 6) and those without (n = 16). Results: Auditory P300 amplitude was reduced in both schizophrenic and EPI- SZ patients, whose positive or negative symptoms did not differ. In contras t, N1 amplitude was reduced only in schizophrenic patients. Delays in both N1 and P300 were associated with epilepsy patients and EPI-SZ but not schiz ophrenic patients. Conclusions: The schizophrenialike symptoms in epilepsy probably represent a phenocopy of schizophrenia with common clinical features and some common pathophysiologies but distinct etiologies, P300 amplitude appears to be sen sitive to schizophrenialike features, regardless of whether they occur in t he context of schizophrenia ol epilepsy. N1 amplitude reduction appears to be specific to schizophrenia, suggesting its sensitivity to the distinct et iology of schizophrenia.