Dimensions of Executive Functioning in Schizophrenia and Their Relationship With Processing Speed

Abstract

Context:The nature of executive dysfunction in schizophrenia is nebulous, due to inconsistencies in conceptualizing and operationalizing the construct, and the broader question of whether schizophrenia is best characterized in terms of specific vs generalized cognitive deficits. The current study aimed to determine whether executive functions represent unitary vs diverse constructs in schizophrenia. Methods: Participants included 145 community-dwelling individuals with schizophrenia. Executive functions were measured with the Delis-Kaplan Executive Functioning System (D-KEFS). We conducted an exploratory factor analysis (EFA) with principal axis factoring, as well as parallel analyses to examine the latent constructs underlying the D-KEFS tasks, a second EFA on weighted residuals of the D-KEFS tasks (after accounting for processing speed measured with the Digit Symbol task), and bivariate correlations to examine relationships between the D-KEFS components and relevant demographic and clinical variables, crystallized verbal knowledge, and functional capacity. Results: EFA of the D-KEFS tasks yielded 2 factors (cognitive flexibility/timed tests and abstraction). EFA of the processing speed-weighted D-KEFS residuals also yielded 2 factors (cognitive flexibility and abstraction). Cognitive flexibility was negatively correlated with psychopathology. Better abstraction was associated with higher education, shorter illness duration, and better functional capacity. Both factors were positively correlated with crystallized verbal knowledge. Conclusions: Executive functions in schizophrenia could be parsed into 2 partially related but separable subconstructs. Future efforts to elucidate functional outcomes as well as neurobiological underpinnings of schizophrenia may be facilitated by attending to the distinction between cognitive flexibility and abstraction.

Cognitive profiles in persons with chronic schizophrenia

“…For instance, recent findings from our research group based on an independent sample (Savla, Twamley, Delis, et al, 2010; Savla, Twamley, Thompson, et al, 2010) suggest that the mental flexibility and abstraction components of executive function may be at least partially independent, and that severity of deficits on some mental flexibility tasks may be more common than among others. Those findings were based on a large battery of executive function tests designed to permit distinguishing different aspects of executive function, whereas the present battery did not include sufficient numbers of tests of each type of executive function to examine those two types separately.…”

“…Our research group has previously reported factor analyses of a larger neurocognitive battery in schizophrenia (Gladsjo et al, 2004), as well as a more recent study focused on the factor structure of a large battery of tests specifically within the domain of executive functions (Savla, Twamley, Delis, et al, 2010). However, those studies were focused on identifying meaningful groupings of cognitive tests; the present study (based on a sample independent from the other studies) is focused on identifying cognitive groupings patients.…”

Effects of COMT genotype on cognitive ability and functional capacity in individuals with schizophrenia

“…Everyday functional skills were evaluated with the UCSD Performance-Based Skills Assessment, (UPSA; Patterson et al, 2001), which assesses capacity to perform tasks necessary for independent living, related to finances, communication, recreation planning, transportation, and household chores. Neurocognitive assessments included the American National Adult Reading Test (ANART; Grober and Sliwinski, 1991), an oral reading test measuring crystallized verbal knowledge and therefore used as an estimate of premorbid IQ; the Brief Visuospatial Memory Test-Revised (BVMT-R; Benedict, 1997) and Hopkins Verbal Learning Test-Revised (HVLT-R; Brandt and Benedict, 2001) Delis et al, 2001), a nine-subtest battery assessing multiple aspects of executive functioning that load on two factors, cognitive flexibility and abstraction (Savla et al, 2012).…”

The Puzzle of Processing Speed, Memory, and Executive Function Impairments in Schizophrenia: Fitting the Pieces Together

“…However, this interpretation only holds true if those cognitive processes, which are required to complete the digit-symbol substitution task, are truly synonymous with processing-speed ability. Indeed evidence is now accruing which suggests that perhaps digit-symbol substitution performance is reliant on more complex cognitive abilities such as memory and executive function (5-9). Were this the case it would necessitate a re-evaluation of the meaning of the digit-symbol substitution impairment in schizophrenia.…”