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Dedifferentiation and substitute strategy: deconstructing the processing-speed impairment in schizophrenia.

ABSTRACT: BACKGROUND:Recent research has identified impairment in processing speed, measured by the digit-symbol substitution task, as central to the cognitive deficit in schizophrenia. However, the underlying cognitive correlates of this impairment remain unknown. METHODS:A sample of cases (N=125) meeting DSM-IV criteria for schizophrenia and a sample of community controls (N=272) from the same geographical area completed a set of putative measures of processing-speed ability to which we implemented confirmatory factor and structural regression modelling in order to elucidate the latent structure of processing speed. Next, we tested the degree to which the structural and relational portions of the model were equal across groups. RESULTS:Processing-speed ability was best defined, in both controls and cases (?(2)=38.59(26), p=0.053), as a multidimensional cognitive ability consisting of three latent factors comprising: psychomotor speed, sequencing and shifting, and verbal fluency. However, cases exhibited dedifferentiation (i.e., markedly stronger inter-correlations between factors; ?(2)=59.94(29), p<.01) and a reliance on an alternative ensemble of cognitive operations to controls when completing the digit-symbol substitution task. CONCLUSION:Dedifferentiation of processing-speed ability in schizophrenia and subsequent overreliance on alternative (and possibly less than optimal) cognitive operations underlies the marked deficit observed on the digit-symbol substitution task.

SUBMITTER: Knowles EE

PROVIDER: S-EPMC4196269 | biostudies-literature | 2012 Dec

REPOSITORIES: biostudies-literature

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Dedifferentiation and substitute strategy: deconstructing the processing-speed impairment in schizophrenia.

Knowles Emma E M EE Weiser Mark M David Anthony S AS Dickinson Dwight D Glahn David D Gold James J Davidson Michael M Reichenberg Abraham A

Schizophrenia research 20121017 1-3

<h4>Background</h4>Recent research has identified impairment in processing speed, measured by the digit-symbol substitution task, as central to the cognitive deficit in schizophrenia. However, the underlying cognitive correlates of this impairment remain unknown.<h4>Methods</h4>A sample of cases (N=125) meeting DSM-IV criteria for schizophrenia and a sample of community controls (N=272) from the same geographical area completed a set of putative measures of processing-speed ability to which we i ...[more]

PMID: 23084540

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Project description:BACKGROUND:In most domains of cognition, individuals with schizophrenia are generally found to be one standard deviation below the mean of the controls. As a result, examining the impact of cognitive remediation in individuals with schizophrenia has been a burgeoning area of research. However, the state of the literature remains unclear as to which domains of cognition should be targeted to produce the most widespread and durable benefits for individuals with schizophrenia. One suggestion is that targeting lower-level cognitive processes that are important for higher-level and more complex aspects of cognition may produce the most widespread benefits in cognition and everyday functioning. Relatively few studies have examined the effects of working memory or processing speed training in schizophrenia, as most studies examine broad-based remediation programs. Thus, a need exists for targeted working memory and processing speed training studies to better understand the mechanisms of cognitive enhancement in patients. This study aims to 1) investigate near-transfer gains (that is, the transfer of learning to related contexts) associated with working memory and processing speed training in schizophrenia patients; 2) investigate far-transfer gains (that is, the transfer of learning to new contexts) associated with working memory and processing speed training (that is, gains in other neurocognitive domains and social cognition); and 3) investigate real-world gains associated with training (that is, gains in daily functioning). METHODS/DESIGN:A double-blind randomized controlled trial with a three parallel group design will be conducted. A random sample of 81 patients with schizophrenia or schizoaffective disorder will be recruited through outpatient clinics at Foothills Hospital and community support programs in Calgary, Alberta. Participants will be randomly assigned using a computer-generated program in a 1:1:1 ratio to a working memory-training group, a processing speed-training group, or a no-training control group. Training will be completed at home for 30 minutes per day, 5 days per week, for a total of 10 weeks. Neurocognitive, social cognitive, and daily functioning measures will be administered both pre- and post-training to detect training-related gains. The primary outcome measures will include working memory and processing speed (near-transfer measures), as well as fluid intelligence (far-transfer measure). TRIAL REGISTRATION:Current controlled trials NCT02478827 (ClinicalTrials.gov, registered on 15 June 2015).

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Dedifferentiation and substitute strategy: deconstructing the processing-speed impairment in schizophrenia.

Publications

Dedifferentiation and substitute strategy: deconstructing the processing-speed impairment in schizophrenia.

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