Schizophrenia: Cognitive Deficits and Perceptual Deficits

Schizophrenia is a complex and severe mental disorder that affects about 1% of the population, clinically characterized by positive, negative, and disorganized symptoms. It is widely accepted that a combination of genetic and environmental factors lead to the onset of schizophrenia. The past two decades have witnessed the increasingly important role of cognitive deficits in schizophrenia, such as attentional problems, impaired working memory, and abnormal executive functioning. Indeed, cognitive deficits are better at predicting the prognosis of schizophrenia than clinical symptoms. Although perceptual processes play a crucial role in cognition, very little is known about how abnormal perception may lead to cognitive deficits. But there is evidence suggesting that impaired perceptual processing may interact with or mediate cognitive deficits, although degraded perceptual processing is not necessarily associated with cognitive deficits. Perceptual abnormalities in schizophrenia have been well documented in the visual system. Clinically, a considerable portion of schizophrenia patients (up to 60%) report distorted visual experience such as perception of motion, color, size, and facial expression. Visual deficits include poor performance on visual detection and/or discrimination task, altered visual backward masking (VBM) effect, decreased contrast sensitivity, impaired motion perception, and poor discrimination of biological motion. Since high-quality, accurate input to the sensory cortices would determine subsequent processing by heteromodal association cortices, elucidating the extent of perceptual deficits in schizophrenia is a fundamentally important task. Received: May 23, 2011 / Revised: June 2, 2011 Accepted: June 7, 2011 Address for correspondence: Jejoong Kim, Department of Brain and Cognitive Sciences, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea Tel: 02-880-2863, Fax: 02-871-9129 E-mail: [email protected] This work was supported by the World Class University program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (R32-10142). Visual Perception Deficits Associated with the Magnocellular Pathway in Schizophrenia