Investigating the Latent Structure of Executive Function in the Delis-Kaplan Executive Function System Using Cattell-Horn-Carroll Theory.

OBJECTIVE: To replicate a seven-factor model previously reported for the Delis-Kaplan Executive Function System (D-KEFS). METHOD: This study used the D-KEFS standardization sample including 1,750 non-clinical participants. Several seven-factor models previously reported for the D-KEFS were re-evaluated using confirmatory factor analysis (CFA). Previously published bi-factor models were also tested. These models were compared with a three-factor a priori model based on Cattell-Horn-Carroll (CHC) theory. Measurement invariance was examined across three age cohorts. RESULTS: All previously reported models failed to converge when tested with CFA. None of the bi-factor models converged after large numbers of iterations, suggesting that bi-factor models are ill-suited to represent the D-KEFS scores as reported in the test manual. Although poor fit was initially observed for the three-factor CHC model, inspection of modification indices showed potential for improvement by including method effects via correlated residuals for scores derived from similar tests. The final CHC model showed good to excellent fit and strong metric measurement invariance across the three age cohorts with minor exceptions for a subset of Fluency parameters. CONCLUSIONS: CHC theory extends to the D-KEFS, supporting findings from previous studies that executive functions can be integrated into CHC theory.

Regression-based normative data for the D-KEFS Color-Word Interference Test in Norwegian adults ages 20-85.

Objective: The Delis-Kaplan Executive Function System (D-KEFS) Color-Word-Interference Test (CWIT; AKA Stroop test) is a widely used measure of processing speed and executive function. While test materials and instructions have been translated to Norwegian, only American age-adjusted norms from D-KEFS are available in Norway. We here develop norms in a sample of 1011 Norwegians between 20 and 85 years. We provide indexes for stability over time and assess demographic adjustments applying the D-KEFS norms. Method: Participants were healthy Norwegian adults from Center for Lifespan Changes in Brain and Cognition (LCBC) (n = 899), the Dementia Disease Initiation (n = 77), and Oslo MCI (n = 35). Using regression-based norming, we estimated linear and non-linear effects of age, education, and sex on the CWIT 1-4 subtests. Stability over time was assessed with intraclass correlation coefficients (ICC). The normative adjustment of the D-KEFS norms was assessed with linear regression models. Results: Increasing age was associated with slower completion on all CWIT subtests in a non-linear fashion (accelerated lowering of performance with older age). Women performed better on CWIT-1&3. Higher education predicted faster completion time on CWIT-3&4. The original age-adjusted norms from D-KEFS did not adjust for sex or education. Furthermore, we observed significant, albeit small effects of age on all CWIT subtests. ICC analyses indicated moderate to good stability over time. Conclusion: We present demographically adjusted regression-based norms and stability indexes for the D-KEFS CWIT subtests. US D-KEFS norms may be inaccurate for Norwegians with high or low educational attainment, especially women.

Executive Function and Processing Speed in Children Living with Sickle Cell Anemia.

Executive function and processing speed difficulties are observed in children living with sickle cell anemia (SCA). The influence of processing speed on executive function is not well understood. We recruited 59 children living with SCA and 24 matched controls aged 8-18 years between 2010 and 2016 from clinics in the UK. Children completed tests in processing speed and cognitive flexibility, subdomains of executive function. MRI scans were conducted within one year of testing; oxygen saturation was obtained on the day of testing. Hemoglobin levels were obtained from medical records. Caregivers completed the executive function questionnaire. Hierarchical linear regressions found that hemoglobin, oxygen saturation, age, infarct status, and processing speed were not independent predictors for any model. However, for all cognitive flexibility tests, there was a significant interaction between infarct status and processing speed; children without silent cerebral infarction (SCI) with faster processing speed had better cognitive flexibility. Our findings indicate that, when interpreting executive function difficulties, it is important to account for the relationship between SCI status and processing speed. More research is needed to elucidate the mechanisms, but clinically, including executive function testing as part of clinic visits by embedding psychologists within the healthcare team would appear to be a critical step.

Multivariate models provide an effective psychometric solution to the variability in classification accuracy of D-KEFS Stroop performance validity cutoffs.

ObjectiveThe study was designed to expand on the results of previous investigations on the D-KEFS Stroop as a performance validity test (PVT), which produced diverging conclusions. Method The classification accuracy of previously proposed validity cutoffs on the D-KEFS Stroop was computed against four different criterion PVTs in two independent samples: patients with uncomplicated mild TBI (n = 68) and disability benefit applicants (n = 49). Results Age-corrected scaled scores (ACSSs) ≤6 on individual subtests often fell short of specificity standards. Making the cutoffs more conservative improved specificity, but at a significant cost to sensitivity. In contrast, multivariate models (≥3 failures at ACSS ≤6 or ≥2 failures at ACSS ≤5 on the four subtests) produced good combinations of sensitivity (.39-.79) and specificity (.85-1.00), correctly classifying 74.6-90.6% of the sample. A novel validity scale, the D-KEFS Stroop Index correctly classified between 78.7% and 93.3% of the sample. Conclusions A multivariate approach to performance validity assessment provides a methodological safeguard against sample- and instrument-specific fluctuations in classification accuracy, strikes a reasonable balance between sensitivity and specificity, and mitigates the invalid before impaired paradox.

Comparison of language awareness in Kurdish-Persian bilingual children and Persian monolingual children.

The present study examines language awareness between bilinguals and monolingual children. Language awareness is a person's explicit understanding of language and its role in thinking, learning, and social life, which is associated with executive functioning. Delis-Kaplan Executive Function System (D-KEFS) test was designed to evaluate executive functioning. The test includes two parts: verbal and non-verbal. In this study, the verbal part including Twenty Questions, Word context, and proverb of D-KEFS was used. Kurdish-Persian bilinguals and Persian monolinguals attended this study. The results showed that in the Twenty Questions, word context, and proverb, there was a significant difference between bilinguals and monolinguals. Bilinguals outperformed monolinguals in both twenty-question and word context tests, while they performed lower on the proverb test. It can be concluded that bilingualism affects language awareness and also influences different aspects of executive functioning in different manners.

Can executive functions of the brain predict official driving test success?

Human factors, including the level of cognitive functioning, are the most influential factors in road traffic crashes. Among cognitive abilities, executive functions (EFs) of the brain play a pivotal role in driving performance and outcomes, including crash numbers. The current study was aimed to explore, for the first time, the ability of EF tests to predict success on the official driving tests in applicants of driving license in Iran. We administered a relevant set of commonly used EF tests, including a computerized Stroop test and six tests from the Delis-Kaplan Executive Function System (D-KEFS) and the Behavioral Assessment of the Dysexecutive Syndrome (BADS), to 87 healthy new drivers applying for a driver's license (Mage = 25.9 years, SD = 8.2; 43 female). We also administered a series of demographic and psychological questionnaires. The data regarding the participants' official driving tests were extracted from the official records. To determine the relations of the EF tests with success on the driving tests, several correlation and regression analyses were conducted. Most of the EF measures had significant correlations with the road test success, while having no significant relations with the theory test success. Moreover, in our regression analyses, The EF measures predicted success on the official driving road test, but not success on the driving theory test, even after controlling for the effects of previous unlicensed driving experience and stress symptoms. The results demonstrate the predictability of the driving road test success from executive functioning.

Ecological validity of executive function tests in predicting driving performance.

Almost all of our everyday activities depend on executive function (EF) skills. In line with the increasing attention to the ecological validation of neuropsychological assessment and intervention methods, this study aimed to explore the ecological validity of a relevant set of widely used EF tests, mostly from well-known paradigms of EF assessment, in predicting driving ability. Ninety-six healthy novice drivers (Mage = 26.2 years, SD = 8.4; 48 female) completed four stages of our data collection including psychological, EF, and driving assessments. For the psychological assessment, validated measures of sensation-seeking, risk-taking, personality traits, ADHD symptoms, depression, anxiety, and stress were administered. For the EF assessment, selected tests from the Delis-Kaplan Executive Function System (D-KEFS: Trail Making, Design Fluency, and Tower) and the Behavioral Assessment of the Dysexecutive Syndrome (BADS: Key Search, Zoo Map, and Modified Six Elements) along with a computerized Stroop test were administered. For the driving assessment, we used a simulated driving test comprising of 14 key dimensions of driving skills. Several correlations and multiple regression analyses were conducted. Significant correlations were found between all the EF measures and driving performance. Moreover, the EF measures predicted the driving ability over and above the effects of previous driving experience and the psychological variables. These results provide supporting evidence for the ecological validity of the EF tests in predicting driving performance. The incorporation of assessment and intervention targeting multiple domains of EF into driving rehabilitation and education programs could be a focus of future research.

Evaluation of post-traumatic stress disorder (PTSD) and related comorbidities in clinical studies.

Patients with traumatic brain injury (TBI) of varying severities are experiencing adverse outcomes during and after rehabilitation. Besides depression and anxiety, post-traumatic stress disorder (PTSD) is highly encountered in civilian and military populations. As more prospective and retrospective studies - focused on evaluating new or old psychological therapies in inpatient, outpatient, or controlled environments, targeting patients with PTSD with or without a history of TBI - are carried out, researchers are employing various scales to measure PTSD as well as other psychiatric diagnoses or cognitive impairments that might appear following TBI. We aimed to explore the literature published between January 2010 and October 2021 by querying three databases. Our preliminary results showed that several scales - such as the Clinician-Administered PTSD Scale (CAPS), the Posttraumatic Stress Disorder Checklist Military Version (PCL-M) as well as Specific Version (PCL-S), and Civilian Version (PCL-C) - have been frequently used for PTSD diagnosis and symptom severity. However, heterogeneity in the scales used when assessing and evaluating additional psychiatric comorbidities and cognitive impairments are due to the study aim and therapeutic approaches. Therefore, conducting an intervention focusing on post-TBI PTSD patients requires increased attention to patients' medical history in capturing multiple cognitive impairments and affected neuropsychological processes when designing the study and including validated instruments for measuring primary and secondary neuropsychological outcomes.

D-KEFS trail making test as an embedded performance validity measure.

OBJECTIVE: The Delis-Kaplan Executive Function System (D-KEFS) Trail Making Test (TMT) is a commonly used measure of processing speed and executive functioning that may also be useful as an embedded performance validity test (PVT). We evaluated the utility of several multi-condition indices on the D-KEFS TMT in three independent samples to determine an optimal multi-condition index and cutoff on the D-KEFS TMT. METHOD: Classification accuracy statistics for multiple multi-condition indices on the D-KEFS TMT were evaluated in three independent samples, including a sample with history of mild traumatic brain injury (TBI; n = 267) classified into psychometrically defined performance-valid and performance-invalid subgroups, the D-KEFS national normative sample (n = 1713), and a sample of middle- and older-aged adults diagnosed with mild cognitive impairment (MCI; n = 70). RESULTS: The D-KEFS TMT Conditions 1-5 summation index maximized sensitivity at .31 while maintaining adequate specificity at ≥.9. This index also had acceptable classification accuracy in both the D-KEFS national normative and MCI cross-validation samples, with the exception of the oldest subgroup of the national norming sample (i.e., individuals' ages 80-89), in which the observed failure rates for all multi-condition indices tested were greater than 10%. CONCLUSION: Our study provides support for the use the D-KEFS TMT Conditions 1-5 summation index as an embedded PVT among individuals younger than 80 years-old and from a range of conditions spanning from cognitively normal to mildly impaired; however, further validation is necessary.

The Factorial Structure of the Tower Test From the Delis-Kaplan Executive Function System: A Confirmatory Factor Analysis Study.

The Tower of London (TOL) is a well-known, widely used task that captures executive function abilities. We examined the factorial structure and discriminant validity of three measures extracted from the Delis-Kaplan Executive Function System (D-KEFS) version of the TOL, namely the D-KEFS Tower Test, in 270 individuals from a publicly available release of the Enhanced Nathan Kline Institute-Rockland sample. Confirmatory factor analyses revealed a multidimensional three-factor solution of the measures extracted from the D-KEFS Tower Test; first-move-time, excess moves, and rule violations. This model was better than the unidimensional model, the two-factor model, the bifactor model and the model that included the total achievement scores. These results support the discriminant validity of the three latent factors, over their distinct relations to the total achievement score. The best fitting model was gender-invariant and age-variant. Overall, the multidimensionality of the measures extracted from the D-KEFS Tower Test reflects the need to use multiple metrics from this version of TOL to capture executive functions instead of a single score.

Offering alphabet support in the Trail Making Test: Increasing validity for participants with insufficient automatization of the alphabet.

Insufficient automatization of the alphabet may falsely impair performance on the Trail Making Test among persons with dyslexia or persons not accustomed to the Latin alphabet. We analyze whether writing the alphabet on top of the test sheet changes performance in these risk groups, and whether alphabet support reduces the complexity of the set-shifting task.One-hundred and seventy patients referred to neuropsychological assessment participated and were given both a TMT-version offering alphabet support and the D-KEFS TMT. The discrepancy between the D-KEFS subtask where lines are drawn successively between numbers only, and the task where lines are drawn between letters only, was operationalized as measuring insufficient alphabet automatization.Both the possible dyslexia group, and persons taught to read with another alphabet, had a larger discrepancy score than the remaining sample. Regression analyses showed that the discrepancy scores explained 3.4% of the variance beyond age and speed when giving alphabet support. The corresponding percentage for the D-KEFS Switching task was 17.5%. The findings indicate that alphabet support alleviated effects of non-automatization. The TMT-B-NR: TMT-A ratio score was equivalent to what is found when not applying alphabet support, showing that alphabet support did not contaminate the test as a EF-measure.

Factor-Analytic Evidence for the Complexity of the Delis-Kaplan Executive Function System (D-KEFS).

This study examined the complexity of the Delis-Kaplan Executive Function System both in terms of the overall number of factors needed to model the entire battery and the complexity of the number of factors needed to model individual tests. The correlations between tests from the Delis-Kaplan Executive Function System standardization sample were modeled with varying numbers of factors. Simulations of test scores were also done that varied the number of factors used to generate the data and considered criteria for factor retention based on eigenvalues, fit indices, and generalization to new data. The results show seven-factor solutions based on generalization of fixed weights to validation samples provided best estimates. Modification indices produced three seven-factor solutions with comparable model fit but markedly different factor loadings. These results are consistent with process overlap theory, which suggest that complex tests are determined my many distinct executive processes. Given uncertainty of factor-analytic solutions, interpretation of the meaning of test scores should be based on evidence that is external to the test items, such as their sensitivity to clinical conditions. Overly simplistic interpretations of executive test performance based on factor-analytic results are not warranted. This is consistent with the cognitive processing approach of the test authors.

Utility of the D-KEFS Color Word Interference Test as an embedded measure of performance validity.

Objective: The D-KEFS Color Word Interference Test (CWIT) is among the most commonly administered measures of verbally mediated processing speed and executive functioning. Previous research suggests that this test may also be sensitive to performance invalidity. We sought to develop new embedded measures of performance invalidity based on multi-condition performance on the CWIT and to evaluate previously proposed embedded measures for performance invalidity on this test.Method: Newly developed and previously proposed embedded measures were evaluated in three samples: a traumatic brain injury (TBI) sample (N = 224) classified into psychometrically-defined performance-valid and performance-invalid subgroups; the D-KEFS normative sample (N = 1,735); and a Parkinson's disease sample (N = 166). To explore the resilience of CWIT cutoffs to the effects of age and neurocognitive impairment, the D-KEFS normative sample was stratified into age groups of 8-19, 20-69, and 70-89 and the Parkinson's disease sample into normal cognition, mild cognitive impairment, and dementia groups.Results: Our newly developed embedded measures derived from within the TBI sample were largely resilient to the effects of age and neurocognitive impairment other than dementia. Overall, a cutoff of ≤18 on the sum of age-corrected scaled scores on all four conditions exhibited the strongest classification accuracy. In contrast, previously proposed cutoffs (Erdodi et al., 2018) produced unacceptable false-positive rates within the TBI sample and generally a high rate of potential false positives in the normative age and clinical groups.Conclusion: Scoring ≤18 on the sum of all conditions on the CWIT appears to be an optimal cutoff for performance invalidity detection in non-demented samples.

Neuropsychological functioning following surgery for pediatric low-grade glioma: a prospective longitudinal study.

OBJECTIVE: High survival rates have led to an increased emphasis on the functional outcomes of children diagnosed with low-grade glioma. Most outcomes research has focused on risks associated with radiotherapy, but less is known about neuropsychological risks for patients treated with surgery alone. Here, the authors sought to examine the neuropsychological trajectories of children diagnosed with a low-grade glioma and monitored up to 6 years postsurgery. Secondarily, they explored demographic and clinical predictors of neuropsychological performance. METHODS: The neuropsychological functioning of 32 patients (median age at diagnosis 10.0 years) was prospectively assessed annually for up to 6 years after surgery (median days from surgery at baseline = 72). Tumor location was predominately supratentorial (65.6%). A combination of performance-based and parent-reported measures was used to assess intelligence, memory, executive functioning, and fine motor control in all patients. RESULTS: Binomial tests at the postoperative baseline revealed that the proportion of children falling below the average range (< 16th percentile) was significantly higher than the rate expected among healthy peers on measures of verbal memory, processing speed, executive functioning, and fine motor control (p < 0.05). Even so, linear mixed models indicated that neuropsychological functioning at the postoperative baseline did not significantly change over time for up to 6 years after surgery across all domains. A larger tumor size was associated with a slower reaction time (p < 0.01). A supratentorial tumor location and history of seizures were associated with more parent-reported executive difficulties (p < 0.01). CONCLUSIONS: While radiotherapy is a known risk factor for neuropsychological deficits in pediatric brain tumor patients, findings in this study indicate that children treated for low-grade glioma with surgery alone (without radiotherapy or chemotherapy) remain susceptible to difficulties with memory, executive functioning, and motor functioning that persist over time. Over half of the children in the study sample required school support services to address neuropsychological weaknesses. Although low-grade glioma is often conceptualized as a benign tumor, children treated for this lesion require ongoing monitoring and intervention to address neuropsychological weaknesses resulting from the tumor itself as well as the surgery.

Comparisons of the BRIEF parental report and neuropsychological clinical tests of executive function in Fetal Alcohol Spectrum Disorders: data from the UK national specialist clinic.

Extant literature is sparse with regards to the relationship between caregiver reports and neuropsychological tests of executive functioning in Fetal Alcohol Spectrum Disorders (FASD). The goal of this paper was determining the clinical utilities of executive functioning measures used in the United Kingdom national FASD clinic. We examined relationships between outcomes on the Behavior Rating Inventory of Executive Function (BRIEF) and the Delis-Kaplan Executive Function System (D-KEFS), as part of an ongoing service evaluation. Profiles of executive functioning measures were reported in order to contribute to delineating a profile of executive dysfunction in FASD. Caregivers of 49 people with FASD completed the Parent BRIEF, and 61 people with FASD were administered the D-KEFS. Pearson's Correlations between all 11 BRIEF scales and the 18 selected D-KEFS subscales showed little relationship. The BRIEF showed a profile of clinically significant elevations in all three Index scores and seven out of the eight Scale scores. Several D-KEFS tests showed below average executive functioning. Both executive function measures have separate clinical utility in demonstrating executive function deficits in FASD. The sample population used in this study also show a similar pattern to FASD populations internationally, suggesting a similar neuropsychological profile is seen in the United Kingdom. However, caregiver reports display little relationship to neuropsychological tests. These measures likely monitor different aspects of executive functioning in different settings. Future research should focus on identifying tests that better relate findings from clinical settings to behavior in daily life.

Occupational Status Is Compromised in Adults With ADHD and Psychometrically Defined Executive Function Deficits.

OBJECTIVE: Problems related to executive function (EF) are frequently reported in adults with ADHD. However, only a subgroup of patients show deficits on common neuropsychological tests designed to measure EF. We investigated whether this subgroup also had higher levels of functional impairments, including unemployment, than the ADHD group without such deficits. METHOD: We defined executive function deficit (EFD) from selected tests from the Delis-Kaplan Executive Function System (D-KEFS) and assessed ADHD symptoms and psychiatric comorbidity with the use of questionnaires in 79 ADHD patients and 77 controls (IQ above 80 in both groups). RESULTS: In the ADHD group, 24.3% had EFD. This subgroup showed significantly higher frequency of unemployment, more reading and writing problems, lower IQ scores, and more self-reported ADHD symptoms in childhood than the ADHD subgroup without EFD. CONCLUSION: These findings indicate that it may be possible to identify individuals at risk of functional impairments, and emphasizes the importance of effective treatment programs targeting EF.

Neurocognitive changes in pituitary adenoma patients after Gamma Knife radiosurgery.

OBJECTIVEPituitary adenomas and the treatment required for the underlying neuropathology have frequently been associated with cognitive dysfunction. However, the mechanisms for these impairments remain the subject of much debate. The authors evaluated cognitive outcomes in patients treated with or without Gamma Knife radiosurgery (GKRS) for an underlying pituitary adenoma.METHODSThis was a retrospective, institutional review board-approved, single-institution study. A total of 51 patients (23 male, 28 female) treated for pituitary adenoma were included in this neurocognitive study. Twenty-one patients underwent GKRS following transsphenoidal surgery, 22 patients were treated with transsphenoidal surgery alone, and eight patients were conservatively managed or were treated with medical management alone. Comparisons using psychometric tests of general intellectual abilities, memory, and executive functions were made between the treatment groups, between male and female patients, and between patients with Cushing's disease and those with nonfunctioning adenoma (NFA).RESULTSThe entire patient sample, the NFA group, and the GKRS group scored significantly below expected on measures of both immediate and delayed memory, particularly for visually presented information (p ≤ 0.05); however, there were no significant differences between the patients with Cushing's disease and those with NFA (t ≤ 0.56, p ≥ 0.52). In those who underwent GKRS, memory scores were not significantly different from those in the patients who did not undergo GKRS (t ≤ 1.32, p ≥ 0.19). Male patients across the sample were more likely to demonstrate impairments in both immediate memory (t = -3.41, p = 0.003) and delayed memory (t = -3.80, p = 0.001) than were female patients (t ≤ 1.09, p ≥ 0.29). There were no impairments on measures of general intellectual functioning or executive functions in any patient group. The potential contributions of tumor size and hormone levels are discussed.CONCLUSIONSOverall, pituitary adenoma patients demonstrated relative impairment in anterograde memory. However, GKRS did not lead to adverse effects for immediate or delayed memory in pituitary adenoma patients. Cognitive assessment of pituitary adenoma patients is important in their longitudinal care.

Inhibitory Control, Task/Rule Switching, and Cognitive Planning in Vascular Dementia: Are There Any Differences From Vascular Aging?

Recent studies have shown that patients diagnosed with Vascular Dementia (VaD) exhibit deficits in executive functions. According to "vascular hypothesis of cognitive aging," community-dwelling older adults having risk factors for vascular disease development (RVD) may suffer from cognitive decline of the same type. The aim of the study was to assess the level of specific executive functions (EF) that have been revealed as most affected by vascular abnormalities, in older adults with incipient VaD and RVD. Subsequently specific ways of EF measuring could be suggested for more accurate diagnosis of early stage VaD. The study compared three adult groups (N = 60): (a) patients diagnosed with incipient VaD, according to DSM-5 criteria (n = 20); (b) community-dwelling older adults presenting cardiovascular risk factors (RVD; n = 20); (c) healthy young adult controls (n = 20). Three types of executive functions were examined: inhibitory control, cognitive flexibility as rule/task switching, and planning. The following D-KEFS subtests were administered for their evaluation: The 'Color-Word Interference Test,' the 'Verbal Fluency Test,' and the 'Tower Test.' Mixed-measures ANOVA, MANOVA, and one-way ANOVA as well as Scheffe post hoc test were applied to the data of the scores in each condition of each test. The results showed that VaD patients had significantly lower performance in test conditions requiring switching and planning, compared to RVD group and young controls. The specific deficits of VaD patients, compared to older adults presenting RVD according to multiple-group path analyses were: more uncorrected errors in inhibition, the use of semantic knowledge primarily instead of switching ability to switch between semantic categories, as well as a lower level of movement precision in planning.

Advanced clinical interpretation of the Delis-Kaplan Executive Function System: multivariate base rates of low scores.

OBJECTIVE: Multivariate base rates allow for the simultaneous statistical interpretation of multiple test scores, quantifying the normal frequency of low scores on a test battery. This study provides multivariate base rates for the Delis-Kaplan Executive Function System (D-KEFS). METHOD: The D-KEFS consists of 9 tests with 16 Total Achievement scores (i.e. primary indicators of executive function ability). Stratified by education and intelligence, multivariate base rates were derived for the full D-KEFS and an abbreviated four-test battery (i.e. Trail Making, Color-Word Interference, Verbal Fluency, and Tower Test) using the adult portion of the normative sample (ages 16-89). RESULTS: Multivariate base rates are provided for the full and four-test D-KEFS batteries, calculated using five low score cutoffs (i.e. ≤25th, 16th, 9th, 5th, and 2nd percentiles). Low scores occurred commonly among the D-KEFS normative sample, with 82.6 and 71.8% of participants obtaining at least one score ≤16th percentile for the full and four-test batteries, respectively. Intelligence and education were inversely related to low score frequency. CONCLUSIONS: The base rates provided herein allow clinicians to interpret multiple D-KEFS scores simultaneously for the full D-KEFS and an abbreviated battery of commonly administered tests. The use of these base rates will support clinicians when differentiating between normal variations in cognitive performance and true executive function deficits.

Executive functioning of complicated-mild to moderate traumatic brain injury patients with frontal contusions.

Executive dysfunctions are among the most prevalent neurobehavioral sequelae of traumatic brain injuries (TBIs). Using culturally validated tests from the Delis-Kaplan Executive Function System (D-KEFS: Trail Making, Verbal Fluency, Design Fluency, Sorting, Twenty Questions, and Tower) and the Behavioural Assessment of the Dysexecutive Syndrome (BADS: Rule Shift Cards, Key Search, and Modified Six Elements), the current study was the first to examine executive functioning in a group of Iranian TBI patients with focal frontal contusions. Compared with a demographically matched normative sample, the frontal contusion patients showed substantial impairments, with very large effect sizes (p ≤ .003, 1.56 < d < 3.12), on all the executive measures. Controlling for respective lower-level/fundamental conditions, the differences on the highest-level executive (cognitive switching) conditions were still significant. The frontal patients also committed more errors. Patients with lateral prefrontal (LPFC) contusions were qualitatively worst. For example, only the LPFC patients committed perseverative repetition errors. Altogether, our results support the notion that the frontal lobes, specifically the lateral prefrontal regions, play a critical role in cognitive executive functioning, over and above the contributions of respective lower-level cognitive abilities. The results provide clinical evidence for validity of the cross-culturally adapted versions of the tests.