Difficulties related to inhibition and set-shifting have been suggested as possible endophenotypes of Attention Deficit Hyperactivity Disorder (ADHD). However, such difficulties have not been consistently found in studies using standard neuropsychological tests. This has been partly explained by the complexity of these tests and the need to include contrast measures which control for more basic functions. The purpose of the present study was to examine whether difficulties related to inhibition and set-shifting in adult ADHD patients could be revealed by the Color Word Interference Test (CWIT) from the Delis Kaplan Executive Function System (D-KEFS). A clinically recruited group of adults with ADHD (n = 60) obtained significantly lower scores than population derived controls (n = 60) on both primary summary (p < .001) and contrast measures (p = .004) of set-shifting. The differences between the groups remained statistically significant after controlling for intellectual function and working memory (p = .003). However, no significant differences between the groups were observed on any measure of inhibition. The study indicates that adults with ADHD have specific difficulties with set-shifting as measured by the CWIT, difficulties that probably also reflect problems related to executive function in their daily life. (JINS, 2012, 18, 1–10)

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. (JINS, 2010, 17, 000–000)

To identify neuropsychological and psychosocial factors predictive of amnestic Mild Cognitive Impairment (aMCI) among a group of 94 nondemented older adults, we employed a novel nonlinear multivariate classification statistical method called Optimal Data Analysis (ODA) in a dataset collected annually for 3 years. Performance on measures of memory and visuomotor processing speed or symptoms of depression in year 1 predicted aMCI status by year 2. Performance on a measure of learning at year 1 predicted aMCI status at year 3. No other measures significantly predicted incidence of aMCI at years 2 and 3. Results support the utility of multiple neuropsychological and psychosocial measures in the diagnosis of aMCI, and the present model may serve as a testable hypothesis for prospective investigations of the development of aMCI. (JINS, 2010, 16, 721–729.)

There is increasing recognition that set-shifting, a form of cognitive control, is mediated by different neural structures. However, these regions have not yet been carefully identified as many studies do not account for the influence of component processes (e.g., motor speed). We investigated gray matter correlates of set-shifting while controlling for component processes. Using the Design Fluency (DF), Trail Making Test (TMT), and Color Word Interference (CWI) subtests from the Delis-Kaplan Executive Function System (D-KEFS), we investigated the correlation between set-shifting performance and gray matter volume in 160 subjects with neurodegenerative disease, mild cognitive impairment, and healthy older adults using voxel-based morphometry. All three set-shifting tasks correlated with multiple, widespread gray matter regions. After controlling for the component processes, set-shifting performance correlated with focal regions in prefrontal and posterior parietal cortices. We also identified bilateral prefrontal cortex and the right posterior parietal lobe as common sites for set-shifting across the three tasks. There was a high degree of multicollinearity between the set-shifting conditions and the component processes of TMT and CWI, suggesting DF may better isolate set-shifting regions. Overall, these findings highlight the neuroanatomical correlates of set-shifting and the importance of controlling for component processes when investigating complex cognitive tasks. (JINS, 2010, 16, 640–650.)

This study evaluated cognitive set-shifting in 12 patients with focal lesions in the lateral prefrontal cortex (LPC) by examining their performance on the Trail Making Test from the Delis-Kaplan Executive Function System (D-KEFS). Patients with LPC lesions performed significantly worse than controls on the D-KEFS Trail Making Test on the Letter Sequencing, Number-Letter Switching (set-shifting), and Motor Speed conditions. Patients with LPC lesions performed significantly more slowly on the Number-Letter Switching condition even after controlling for performance on the four baseline conditions of the test. In addition, patients with LPC lesions exhibited significantly elevated error rates on the Number-Letter Switching condition. Results suggest that LPC lesions can lead to impaired cognitive set-shifting on a visual-motor sequencing task. (JINS, 2007, 13, 704–709.)

The purpose of this study was to examine the relationships between lobar volumes and set shifting. We studied 101 subjects, including 36 normal controls, 16 patients with probable Alzheimer's disease, 30 patients with frontotemporal dementia (FTD), and 19 patients with semantic dementia (SD), using a shifting paradigm that carefully controlled for component abilities. Subjects were administered two conditions of the Delis–Kaplan Executive Function System (D-KEFS) Design Fluency Test. In the control condition (DF:Control), examinees generated as many unique designs as possible in 60 s by drawing lines connecting only unfilled dots. In the switching condition (DF:Switch), examinees generated designs by drawing lines alternating between filled and unfilled dots. We used BRAINS2 software to generate volumes of the right and left frontal, temporal, and parietal lobes. Partial correlations and multiple regressions showed that, after controlling for Mini-Mental State Examination and DF:Control, only the right and left frontal lobe volumes significantly correlated with the DF:Switch, most clearly in the FTD and SD groups. Follow-up analyses indicated that frontal contributions to shifting were not related to working memory. Results highlight the importance of carefully controlling for component cognitive processes when studying executive functioning. (JINS, 2007, 13, 386–392.)