title: Local and global limits on visual processing in schizophrenia.
abstract: Schizophrenia has been linked to impaired performance on a range of visual processing tasks (e.g. detection of coherent motion and contour detection). It has been proposed that this is due to a general inability to integrate visual information at a global level. To test this theory, we assessed the performance of people with schizophrenia on a battery of tasks designed to probe voluntary averaging in different visual domains. Twenty-three outpatients with schizophrenia (mean age: 40±8 years; 3 female) and 20 age-matched control participants (mean age 39±9 years; 3 female) performed a motion coherence task and three equivalent noise (averaging) tasks, the latter allowing independent quantification of local and global limits on visual processing of motion, orientation and size. All performance measures were indistinguishable between the two groups (ps>0.05, one-way ANCOVAs), with one exception: participants with schizophrenia pooled fewer estimates of local orientation than controls when estimating average orientation (p = 0.01, one-way ANCOVA). These data do not support the notion of a generalised visual integration deficit in schizophrenia. Instead, they suggest that distinct visual dimensions are differentially affected in schizophrenia, with a specific impairment in the integration of visual orientation information.
authors.affiliation: Institute of Ophthalmology, University College London, London, United Kingdom.
authors.forename: Marc S
authors.initials: MS
authors.lastname: Tibber
authors.affiliation: Institute of Ophthalmology, University College London, London, United Kingdom; UCL Institute of Cognitive Neuroscience, London, United Kingdom.
authors.forename: Elaine J
authors.initials: EJ
authors.lastname: Anderson
authors.affiliation: Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom.
authors.forename: Tracy
authors.initials: T
authors.lastname: Bobin
authors.affiliation: Department of Forensic and Neurodevelopmental Science, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom.
authors.forename: Patricia
authors.initials: P
authors.lastname: Carlin
authors.affiliation: Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom.
authors.forename: Sukhwinder S
authors.initials: SS
authors.lastname: Shergill
authors.affiliation: Department of Optometry & Vision Science, University of Auckland, Private Bag, Auckland, New Zealand.
authors.forename: Steven C
authors.initials: SC
authors.lastname: Dakin
mesh_terms: D000328:Adult; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology*; D009483:Neuropsychological Tests; D009949:Orientation / Q000502:physiology; D012559:Schizophrenia / Q000503:physiopathology*; D012565:Schizophrenic Psychology