Journal
VISUAL NEUROSCIENCE
Volume 24, Issue 2, Pages 183-189Publisher
CAMBRIDGE UNIV PRESS
DOI: 10.1017/S0952523807070253
Keywords
schizophrenia; high-risk mental state; prodrome; visual perception; magnocellular pathways; contrast sensitivity
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Evidence suggests that patients with schizophrenia show impaired performances on tests assessing the magnocellular (M) visual pathway. The aim of this study was to investigate M pathway functioning in persons at high-risk of psychosis. Sixteen high-risk persons at the prodromal phase of psychosis and 20 healthy controls participated. Two types of contrast sensitivity measurements were used, during which participants were asked to detect a briefly presented target Gabor patch. In the pulsed-pedestal paradigm, the luminance of the background field was decreased to saturate M pathways and to bias information processing to parvocellular (P) pathways. In the steady-pedestal paradigm, the luminance of the background field was constant and briefly presented targets were processed by the M pathway. Anomalous perceptual experiences were assessed using the Structured Interview for Assessing Perceptual Anomalies (SlAPA). Results revealed that the high-risk persons showed elevated contrast sensitivity during the M pathway test, and normal sensitivity during the P pathway test. The visual SIAPA scores showed significant positive correlations with the M pathway sensitivity values. These results suggest that the high-risk mental state is associated with hyper-reactive M pathways, which may be responsible for some anomalous perceptual experiences, including abnormal intensity of environmental stimuli, feelings of being flooded and inundated, and inability to focus attention to relevant details.
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