Executive functioning in schizophrenia: Unique and shared variance with measures of fluid intelligence

Martin A.K, Mowry, B, Reutens, D and Robinson, G.A (2015) Executive functioning in schizophrenia: Unique and shared variance with measures of fluid intelligence. Brain and Cognition, 99 57-67. doi:10.1016/j.bandc.2015.07.009

Author Martin A.K
Mowry, B
Reutens, D
Robinson, G.A
Title Executive functioning in schizophrenia: Unique and shared variance with measures of fluid intelligence
Journal name Brain and Cognition   Check publisher's open access policy
ISSN 1090-2147
Publication date 2015-10-01
Year available 2015
Sub-type Article (original research)
DOI 10.1016/j.bandc.2015.07.009
Open Access Status Not Open Access
Volume 99
Start page 57
End page 67
Total pages 11
Place of publication Maryland Heights, United States
Publisher Academic Press
Language eng
Formatted abstract
Objective: Patients with schizophrenia often display deficits on tasks thought to measure “executive” processes. Recently, it has been suggested that reductions in fluid intelligence test performance entirely explain deficits reported for patients with focal frontal lesions on classical executive tasks. For patients with schizophrenia, it is unclear whether deficits on executive tasks are entirely accountable by fluid intelligence and representative of a common general process or best accounted for by distinct contributions to the cognitive profile of schizophrenia.

Method: In the current study, 50 patients with schizophrenia and 50 age, sex and premorbid intelligence matched controls were assessed using a broad neuropsychological battery, including tasks considered sensitive to executive abilities, namely the Hayling Sentence Completion Test (HSCT), word fluency, Stroop test, digit-span backwards, and spatial working memory. Fluid intelligence was measured using both the Matrix reasoning subtest from the Weschler Abbreviated Scale of Intelligence (WASI) and a composite score derived from a number of cognitive tests.

Results: Patients with schizophrenia were impaired on all cognitive measures compared with controls, except smell identification and the optimal betting and risk-taking measures from the Cambridge Gambling Task. After introducing fluid intelligence as a covariate, significant differences remained for HSCT suppression errors, and classical executive function tests such as the Stroop test and semantic/phonemic word fluency, regardless of which fluid intelligence measure was included.

Conclusions: Fluid intelligence does not entirely explain impaired performance on all tests considered as reflecting “executive” processes. For schizophrenia, these measures should remain part of a comprehensive neuropsychological assessment alongside a measure of fluid intelligence.
Keyword Cognition
Frontal lobes
Word fluency
Fluid intelligence
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

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