Evaluation of Specific Executive Functioning Skills and the Processes Underlying Executive Control in Schizophrenia

Abstract

Schizophrenia is associated with executive dysfunction. Yet, the degree to which executive functions are impaired differentially, or above and beyond underlying basic cognitive processes is less clear. Participants included 145 matched pairs of individuals with schizophrenia (SCs) and normal comparison subjects (NCs). Executive functions were assessed with 10 tasks of the Delis-Kaplan Executive Function System (D-KEFS), in terms of “achievement scores” reflecting overall performance on the task. Five of these tasks (all measuring executive control) were further examined in terms of their basic component (e.g., processing speed) scores and contrast scores (reflecting residual higher order skills adjusted for basic component skills). Group differences were examined via multivariate analysis of variance. SCs had worse performance than NCs on all achievement scores, but the greatest SC-NC difference was that for the Trails Switching task. SCs also had worse performance than NCs on all basic component skills. Of the executive control tasks, only Trails Switching continued to be impaired after accounting for impairments in underlying basic component skills. Much of the impairment in executive functions in schizophrenia may reflect the underlying component skills rather than higher-order functions. However, the results from one task suggest that there might be additional impairment in some aspects of executive control.

Does cognitive performance map to categorical diagnoses of schizophrenia, schizoaffective disorder and bipolar disorder? A discriminant functions analysis

“…Nonetheless, work from our group and others shows that executive performance impairments in SZ reflect in part, component process impairments Savla et al, 2011). Thus, it could be argued that the lack of group discrimination on the basis of these domains seen here, actually reflects the compounding effect of a more extreme combined impairment of the component memory and speed of information processing skills in the SZ group.…”

Neuropsychological functioning in late-life depression

“…The CWIT 4 was designed to be the most difficult part of the test (Delis et al, 2005). But several studies question the validity of the CWIT 4 as an equally or more sensitive test of executive impairment than the CWIT 3 in clinical groups (Lippa and Davis, 2010; Savla et al, 2011). In addition, several patients in our study did not comply with the CWIT 4 at the 3 months follow-up, although they did at baseline.…”

Empirically Defined Patterns of Executive Function Deficits in Schizophrenia and Their Relation to Everyday Functioning: A Person-Centered Approach

“…We were largely influenced by the model proposed in the benchmark study of healthy participants by Miyake and colleagues (2000), but we modified this model in light of the schizophrenia literature (Barch & Smith, 2008; Savla et al, 2011), as investigators have illustrated the difficulties of generalizing models developed with healthy participants to clinical populations (Delis, Jacobson, Bondi, Hamilton, & Salmon, 2003). We also were motivated to include constructs assessed by widely used clinical measures in an attempt to enhance the clinical utility of our results.…”

“…A recent study by Clark, Warman, and Lysaker (2010) used exploratory factor analysis in an outpatient sample of individuals with schizophrenia and identified two separate executive function components of inhibition/set shifting and mental flexibility. Another recent study by Savla et al (2011) examined differences between people with schizophrenia and healthy controls on executive measures from the Delis–Kaplan Executive Function System (D-KEFS; Delis, Kaplan, & Kramer, 2001) and concluded that patients with schizophrenia may be particularly impaired in the mental control and manipulation processes required for the Trail Making Test; difficulties on more complex executive measures of task switching were better explained by lower level deficits, such as inattention or slowed processing speed. Taken together, these studies support the notion of discrete executive components, but their results provide no consensus on the nature of these specific, discrete components.…”