109. N100 and P300 ERP abnormalities in schizophrenia and epilepsy

Abstract

The occurrence of schizophrenia-like symptoms in patients with epilepsy has led to speculations regarding the commonalities between the two disorders, particularly with regard to temporal lobe abnormalities. The N1 and P300 components of the auditory event-related potential (ERP) elicited by infrequently occurring task-related stimuli are commonly reduced in patients with schizophrenia. Whether these reductions are related to the pathophysiological processes specific to schizophrenia or to psychotic symptoms more generally was addressed by comparing patients with schizophrenia (SZ, n = 25), epilepsy with interictal schizophrenia (SZ-EPI, n = 7), epilepsy without psychotic symptoms (EPI, n = 16), and normal controls (n = 32). ERPs were elicited using visual and auditory oddball paradigms involving a task (effortful) and an auditory non-task (automatic) paradigm. SZ-EPI and EPI patients had mixed foci, including right and left, frontal and temporal, unlocalized, partial, and generalized primary epilepsy. Auditory P300 at Pz was reduced in SZ and SZ-EPI, but not in the EPI group as a whole. In contrast, N1 was only reduced in SZ. While automatic P300 was not lateralized in the controls of schizophrenics (SZ and SZ-EPI), it was more reduced at left compared to right temporal lobe sites regardless of epileptic focus in the EPI group. Visual P300 was not reduced in any clinical group. These data suggest that reductions in N1 are specific to the pathophysiological process of schizophrenia, while P300 reduction is more generally associated with psychosis, whether it occurs in schizophrenia or epilepsy.