Neurophysiologic mechanisms of attention deficits in schizophrenia

Background: Despite advances in the pharmacologic treatment of schizophreni a, the neurophysiologic mechanism(s) of disordered attention in schizophren ia remain elusive. Objective: The goal of the present study was to assess s pecific components of attention, including disengagement, movement, re-enga gement, and the inhibitory processes involved their control. Methods: Thirt een chronic schizophrenics from the inpatient and outpatient units of the V eterans Administration Medical Center (New Orleans, LA) and thirteen normal control subjects were administered a saccadic eye movements task. Saccade latency was measured in the presence of contra-lateral distracter stimuli t hat preceded the target onset (Distracter-before), followed the target onse t (Distracter - after) or in the absence of a distracter (No-distracter). I n order to assess the interactive process of fixation disengagement and tar get selection, fixation was either offset before the target (Gap) or it rem ained on in the presence of the target (Overlap). Results: Repeated measure s analysis of variance revealed that saccadic latency in patients with schi zophrenia is prolonged to a greater extent than in normal control subjects in the presence of distracter stimuli. Patients with schizophrenia are also characterized by a greater percentage of error saccades directed to the di stracter, and require a longer latency to "issue" corrective saccades follo wing error saccades. Conclusions: The findings suggest that patients with s chizophrenia are required to invoke volitional control under distracter con ditions, whereas normal control subjects require minimal volitional control . The results are interpreted in terms of the inhibitory mechanisms that re gulate attention.