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Dedifferentiation and substitute strategy: deconstructing the processing-speed impairment in schizophrenia
Emma E M Knowles1, Mark Weiser, Anthony S David
1Department of Psychosis Studies, Institute of Psychiatry, King's College London, United Kingdom. emma.knowles@yale.edu
Schizophrenia Research
|October 23, 2012
Summary
Cognitive processing speed deficits in schizophrenia are linked to a less differentiated cognitive structure and reliance on suboptimal operations, particularly evident in the digit-symbol substitution task.
Area of Science:
- Cognitive neuroscience
- Psychiatry
- Neuropsychology
Background:
- Impaired processing speed, a key cognitive deficit in schizophrenia, has unknown underlying cognitive correlates.
- The digit-symbol substitution task is a common measure for assessing processing speed deficits.
Purpose of the Study:
- To elucidate the latent structure of processing speed.
- To investigate cognitive correlates of processing speed impairment in schizophrenia.
- To compare the structure of processing speed between schizophrenia patients and controls.
Main Methods:
- Confirmatory factor and structural regression modeling were used.
- A sample of 125 schizophrenia patients and 272 community controls completed processing speed measures.
- The equality of the structural and relational model components across groups was tested.
Main Results:
- Processing speed was best defined as a multidimensional ability with three factors: psychomotor speed, sequencing/shifting, and verbal fluency.
- Schizophrenia patients showed dedifferentiation (stronger inter-factor correlations) compared to controls.
- Patients relied on alternative cognitive operations for the digit-symbol substitution task.
Conclusions:
- Dedifferentiation of processing speed ability contributes to schizophrenia's cognitive deficits.
- Overreliance on alternative cognitive operations underlies the digit-symbol substitution task impairment in schizophrenia.
- Understanding these cognitive mechanisms can inform interventions for schizophrenia.
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