Perceptual Category Judgment Deficits are Related to Prefrontal Decision Making Abnormalities in Schizophrenia.

Thomas Weickert

doi:10.3389/fpsyt.2013.00184

Abstract

Previous studies of perceptual category learning in patients with schizophrenia generally demonstrate impaired perceptual category learning; however, traditional cognitive studies have often failed to address the relationship of different cortical regions to perceptually based category learning and judgments in healthy participants and patients with schizophrenia. In the present study, perceptual category learning was examined in 26 patients with schizophrenia and 25 healthy participants using a dot-pattern category learning task. In the training phase, distortions of a prototypical dot pattern were presented. In the test phase, participants were shown the prototype, low and high distortions of the prototype, and random dot patterns. Participants were required to indicate whether the presented dot pattern was a member of the category of dot-patterns previously presented during the study phase. Patients with schizophrenia displayed an impaired ability to make judgments regarding marginal members of novel, perceptually based categories relative to healthy participants. Category judgment also showed opposite patterns of strong, significant correlations with behavioral measures of prefrontal cortex function in patients relative to healthy participants. These results suggest that impaired judgments regarding novel, perceptually based category membership may be due to abnormal prefrontal cortex function in patients with schizophrenia.

Highlights

Category learning and decisions or judgments regarding ensuing category membership are cognitive processes that are integral to our daily lives
CORRELATIONS AMONG CATEGORY JUDGMENT, OTHER COGNITIVE VARIABLES, AND SYMPTOMS In patients with schizophrenia, moderately strong, significant correlations were obtained between correct responding during dotpattern category judgment and measures of the Wechsler Adult Intelligence ScaleRevised (WAIS-R), Wisconsin Card Sorting Test (WCST), Wechsler Memory Scale-Revised (WMS-R), California Verbal Learning Test (CVLT) semantic cluster ratio, letter fluency, and Positive and Negative Syndrome Scale (PANSS)
Based on the Keri [27] finding it was not clear if there was a differential impairment related to prefrontal function with respect to perceptual category learning or if the deficit could have been explained by impaired perceptual ability

Summary

Introduction

Category learning and decisions or judgments regarding ensuing category membership are cognitive processes that are integral to our daily lives. Category formation and decisions regarding category membership have been studied extensively in healthy adults. The prototype hypothesis suggests that information about category membership yields a prototype (or an average of instances), which is stored separately from the individual items contributing to formation of the prototype [1,2,3,4]. The exemplar hypothesis suggests that information regarding category membership may be an emergent factor such that information about common features may accumulate gradually and category formation may occur as a product of the number of exemplars stored in memory [5,6,7,8]. Posner and colleagues [1, 9, 10] introduced a dot-pattern category learning procedure that provided a reductionistic approach to category formation by utilizing ill-defined dot patterns that could be grouped into categories

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Conclusion