title: Deconstructing processing speed deficits in schizophrenia: application of a parametric digit symbol coding test.
abstract: Cognitive processing inefficiency, often measured using digit symbol coding tasks, is a putative vulnerability marker for schizophrenia and a reliable indicator of illness severity and functional outcome. Indeed, performance on the digit symbol coding task may be the most severe neuropsychological deficit patients with schizophrenia display at the group level. Yet, little is known about the contributions of simpler cognitive processes to coding performance in schizophrenia (e.g. decision making, visual scanning, relational memory, motor ability). We developed an experimental behavioral task, based on a computerized digit symbol coding task, which allows the manipulation of demands placed on visual scanning efficiency and relational memory while holding decisional and motor requirements constant. Although patients (n=85) were impaired on all aspects of the task when compared to demographically matched healthy comparison subjects (n=30), they showed a particularly striking failure to benefit from the presence of predictable target information. These findings are consistent with predicted impairments in cognitive processing speed due to schizophrenia patients' well-known memory impairment, suggesting that this mnemonic deficit may have consequences for critical aspects of information processing that are traditionally considered quite separate from the memory domain. Future investigation into the mechanisms underlying the wide-ranging consequences of mnemonic deficits in schizophrenia should provide additional insight.
authors.affiliation: Department of Psychiatry & Biobehavioral Sciences, University of California, Los Angeles, Los Angeles, CA 90095, USA. bachman@psych.ucla.edu
authors.forename: Peter
authors.initials: P
authors.lastname: Bachman
authors.forename: Abraham
authors.initials: A
authors.lastname: Reichenberg
authors.forename: Patrick
authors.initials: P
authors.lastname: Rice
authors.forename: Mary
authors.initials: M
authors.lastname: Woolsey
authors.forename: Olga
authors.initials: O
authors.lastname: Chaves
authors.forename: David
authors.initials: D
authors.lastname: Martinez
authors.forename: Natalie
authors.initials: N
authors.lastname: Maples
authors.forename: Dawn I
authors.initials: DI
authors.lastname: Velligan
authors.forename: David C
authors.initials: DC
authors.lastname: Glahn
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D016022:Case-Control Studies; D003072:Cognition Disorders / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008433:Mathematics; D008875:Middle Aged; D009483:Neuropsychological Tests; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011569:Psychiatric Status Rating Scales; D011930:Reaction Time / Q000502:physiology; D012559:Schizophrenia / Q000150:complications*; D012565:Schizophrenic Psychology