Visual Scanning Deficits in Patients with Schizophrenia
Ziwich, Rachel T.
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Scanning of visual images is widely known to be abnormal in patients with schizophrenia. This impaired processing has been proposed to underlie patients' social and functional impairments. Patients with schizophrenia also show impaired reaction time on visual search tests. The present study was designed to determine whether these deficits, which had previously been tested separately and with simple visual displays, could be replicated when patients performed a visual search task with complex stimuli. Patients with schizophrenia (N = 28) and healthy controls (N = 22) performed a task in which they searched for a picture of a small house key hidden within photographs of natural scenes. The observers' eye movements were recorded while they performed the task. Patients exhibited significantly shorter saccade length and longer fixation duration than controls. Patients also took significantly longer to locate the target key. Separately, contrast sensitivity was measured for participants. Contrast sensitivity was found to be significantly negatively correlated with the time needed to locate a target and the number of targets not found within 30 seconds. The results indicate that visual scanning deficits found in free-viewing tasks also exist in tasks of directed attention, and that deficits in contrast sensitivity impact visual functioning.
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