Neural anomalies during visual search in schizophrenia patients and unaffected siblings of schizophrenia patients.

Schizophrenia patients and their unaffected first-degree relatives exhibit performance deficits on attention tasks, perhaps indicating genetic influence over attentional abnormalities in schizophrenia. To identify anomalous brain function associated with attention in individuals who likely have unexpressed genetic liability for schizophrenia, we studied electrophysiological characteristics of unaffected siblings of schizophrenia patients during a visual serial search task. We gathered behavioral and electrophysiological data from 19 schizophrenia patients, 18 unaffected biological siblings of schizophrenia patients, and 19 nonpsychiatric control participants during performance of the Span of Apprehension (Span) task and a control task. Schizophrenia patients had lower Span task accuracy than the other two groups. Schizophrenia and sibling groups exhibited diminished late positive potentials (P300) over parietal brain regions during Span trials. Compared to control task stimuli, attentional demands of Span stimuli elicited augmented early negative potentials (N1, P2) over posterior brain regions. The degree of augmentation was reduced in schizophrenia patients but not in siblings compared to control subjects. Unaffected siblings of schizophrenia patients appear to modulate early attentional functions of posterior brain regions more effectively than schizophrenia patients but show later electrophysiological anomalies suggestive of abnormal updating of task-relevant information. While the latter may reflect neural mechanisms predisposing performance deficits on attentional tasks, the former may reflect compensatory processes present in unaffected relatives of schizophrenia patients.