Mental flexibility: age effects on switching

Mental flexibility is required to track and systematically alternate between 2 response sets. In this study, 719 individuals, 20 to 89 years old, engaged in 3 different tasks that required verbal and nonverbal cognitive switching. Of importance, each task allowed for independent measurement of component skills that are embedded in the higher level tasks. When gender, education, Full Scale IQ, and component skills were partialed out by multiple regression analyses, significant age effects were revealed for each task. This study provides evidence that executive functions--and verbal and nonverbal cognitive switching in particular--are affected by age independently from age-related changes in component skills. The results are discussed in terms of theories of executive control and neurologic correlates across the adult life span.     

Executive Function Profiles in Pediatric Traumatic Brain Injury

Traumatic brain injury (TBI) results in heterogeneous patterns of neuropsychological impairment. This study investigated heterogeneity in executive function (EF) using the Comprehensive Trail Making Test (CTMT) to evaluate 121 children and adolescents with TBI and 121 matched normal controls. The TBI group performed approximately two standard deviations below controls. Cluster analyses indicated that a three-cluster solution best classified the TBI group and a four-cluster solution best classified controls. Greater impairment in EF was associated with lower intellectual, achievement, and neuropsychological test performance in the TBI group. Results suggest that EF deficits reflected in CTMT performance may be useful for classifying severity of TBI.     

Executive functions in school‐aged children: Potential efficacy of tasks in discriminating clinical groups

The performance of three groups of children on a battery of executive function tasks was investigated. A double dissociation paradigm was used, including six executive function tasks (Wisconsin Card Sorting Test, Matching Familiar Figures Test, visual search, verbal fluency, Tower of Hanoi, and mazes) and two vocabulary tasks (Peabody Picture Vocabulary Test‐Revised and the Boston Naming Test). Executive function was defined as goal‐directed behavior including strategic planning, impulse control, organized search, and flexibility of thought and action. One hundred and fifteen children, aged 6.0 to 12.11 years, participated in the study (36 children with attention deficit hyperactivity disorder, 34 children with developmental language disorder, and 45 nondisabled children). Four main results were found: (a) groups differed on three of the executive function tasks, (b) groups differed on both of the nonexecutive function tasks, (c) the relationship between age and performance was linear, and (d) discriminant function analysis revealed 77% of the cases were correctly classified. Implications of the results for the development of executive functions and the construct validity of executive function tasks are discussed.     

Short-term memory, working memory, and executive functioning in preschoolers: longitudinal predictors of mathematical achievement at age 7 years

This study examined whether measures of short-term memory, working memory, and executive functioning in preschool children predict later proficiency in academic achievement at 7 years of age (third year of primary school). Children were tested in preschool (M age = 4 years, 6 months) on a battery of cognitive measures, and mathematics and reading outcomes (from standardized, norm-referenced school-based assessments) were taken on entry to primary school, and at the end of the first and third year of primary school. Growth curve analyses examined predictors of math and reading achievement across the duration of the study and revealed that better digit span and executive function skills provided children with an immediate head start in math and reading that they maintained throughout the first three years of primary school. Visual-spatial short-term memory span was found to be a predictor specifically of math ability. Correlational and regression analyses revealed that visual short-term and working memory were found to specifically predict math achievement at each time point, while executive function skills predicted learning in general rather than learning in one specific domain. The implications of the findings are discussed in relation to further understanding the role of cognitive skills in different mathematical tasks, and in relation to the impact of limited cognitive skills in the classroom environment.     

Executive processing and attention deficit hyperactivity disorder: an application of the supervisory attentional system

Children with attention deficit hyperactivity disorder (ADHD) display many behaviors consistent with an underlying deficit in executive processes. This study examines Norman and Shallice's (1986) supervisory attentional system (SAS) as an approximation of executive functioning thought to be impaired in ADHD. Fifteen ADHD children were compared to a clinical control sample of learning disabled (LD) children and control children matched for age, gender, and IQ on a series of tasks designed to tap the functions of the SAS. The tasks assessed either the inhibition of a strongly triggered response (Star Counting Test, Hayling Sentence Completion Test, and the Random Generation Test) or impulsive responding in the absence of strong trigger-schema contingencies (Brixton Spatial Anticipation Test). Analyses revealed that the ADHD group was significantly impaired, in comparison to the LD and control groups, on tasks requiring the inhibition of a strongly triggered response. Further support for the fractionation of the SAS is provided by the differential performance of the groups on these tasks.     

Sensitivity of the comprehensive trail making test to traumatic brain injury in adolescents

The current study examined the sensitivity of the Comprehensive Trail Making Test (CTMT Reynolds) to neurocognitive deficits in adolescents with traumatic brain injury (TBI). Participants included 60 adolescents, 30 who had sustained TBI and 30 healthy controls (HC) that were individually matched to the TBI sample on age, gender, ethnicity, and geographical region. For both the TBI and HC groups the mean age was 15.0 years (S.D. = 2.3 years, range = 11–19). The TBI group had a mean IQ of 81.7 (S.D. = 14.9), had sustained moderate to severe brain injury, and was assessed an average of 21.1 months (S.D. = 20.7) following injury. The TBI group performed approximately 2 standard deviations below the control sample mean on each of the five CTMT trails as well as on the composite index and these differences were significant (p < .001). Significant correlations were present between the CTMT trails and clinical variables associated with brain injury severity. Finally, receiver operating characteristic analyses indicated good classification of the TBI and control cases for the CTMT, although some variability in classification accuracy was present among the various trails. Results suggest that the CTMT is sensitive to TBI in adolescents but continued research is needed with larger samples of individuals with TBI and other types of neurological disorders to further establish the present findings.     

Contribution of specific cognitive processes to executive functioning in an aging population

The current study investigated executive function measures emphasizing Alpha Span (ASp) to understand relationships among executive and nonexecutive tasks. Nondemented older participants (N = 417) received a comprehensive cognitive battery. Age and vocabulary adjusted correlations revealed associations among ASp, Wechsler Adult Intelligence Scale--Revised (D. Wechsler, 1981) Digit Span subtests, and fluency tasks. Principal-components analysis with varimax rotation revealed a 4 component solution (86.4% of the variance) with executive variables contributing to all loadings. Calculated component indices were submitted to a regression analysis predicting ASp performance. After accounting for age (6.3% of the variance), Component 3 reflecting brief attention-mental manipulation accounted for 13.4% of ASp variance; Component 1, verbal language ability, 11.5%; Component 2, sustained attention-mental tracking, 1.9%; and Component 4, visuoperceptual spatial organization-planning, 0.9%. Results stress the importance of considering executive and nonexecutive aspects of cognition when conceptualizing executive functioning.     

The Role of Early Parenting in Children's Development of Executive Processes

Using structural modeling, we examined the influence of mothers' verbal input that provided information about associations between objects and actions (scaffolding) at 3 and 4 years of age on children's 6-year executive processing skills. Executive processing skills were measured by search retrieval and independent goal-directed play tasks. A set of 4-year basic skills (language, memory, nonverbal problem solving) considered to be prerequisites for executive processing also were included. Patterns of influence across these variables were examined for 253 children who varied in neonatal complications and in their degree of risk for later developmental problems. Results showed that mothers' early verbal scaffolding at 3 years indirectly influenced both types of executive processing skills at 6 years by directly influencing children's language and nonverbal problem-solving skills at 4 years of age. Four-year scaffolding did not show direct influences on later executive processing skills. The provision of this form of maternal verbal input when children are rapidly developing language appears to support a set of basic skills necessary for later executive processing.     

The role of early parenting in children's development of executive processes

Using structural modeling, we examined the influence of mothers' verbal input that provided information about associations between objects and actions (scaffolding) at 3 and 4 years of age on children's 6-year executive processing skills. Executive processing skills were measured by search retrieval and independent goal-directed play tasks. A set of 4-year basic skills (language, memory, nonverbal problem solving) considered to be prerequisites for executive processing also were included. Patterns of influence across these variables were examined for 253 children who varied in neonatal complications and in their degree of risk for later developmental problems. Results showed that mothers' early verbal scaffolding at 3 years indirectly influenced both types of executive processing skills at 6 years by directly influencing children's language and nonverbal problem-solving skills at 4 years of age. Four-year scaffolding did not show direct influences on later executive processing skills. The provision of this form of maternal verbal input when children are rapidly developing language appears to support a set of basic skills necessary for later executive processing.     

Exploring the roles of the visual‐spatial sketch pad and central executive in children's arithmetical skills: Views from cognition and developmental neuropsychology

Short‐term memory has often been found to play a major role in children's arithmetical skills. However, Bull and Johnston (1997) found that when differences in reading skills were controlled for, short‐term memory, specifically the functioning of the articulatory loop, did not represent a fundamental deficit for children of low mathematical ability. This study examined the role of other working‐memory mechanisms in arithmetical skills, namely the central executive, using the Wisconsin Card Sorting Test (WCST), and the visual‐spatial sketch pad, using the Corsi Blocks. Results showed that children of high and low mathematics ability differed significantly on WCST measures after controlling for differences in reading ability and IQ but did not differ in visual sequential memory. Correlation analyses revealed a significant correlation between arithmetic performance and perseveration measures from the WCST. The implications of this result are discussed in terms of central‐executive functioning and related cognitive and behavioral difficulties.     

Executive functioning in healthy elderly Chinese people.

This study aimed to explore the executive function of healthy elderly Chinese people. A sample of 58 healthy Chinese aged 60 and over was recruited from Guangzhou in China. They were divided into two age groups, a younger age group (aged 60-70) and an older age group (aged over 70). Executive function was measured by a battery of seven tests which were assumed to capture specific components of executive function. The tests were initiation (Hayling Sentence Completion Test (HSC)), sustained attention (Monotone Counting Test), switching and flexibility (word fluency and modified Wisconsin Card Sorting Test (WCST)), disinhibition (Modified Six Element Task (SET), Stroop Test, and HSC), attention allocation and planning (SET and modified version of WCST), and updating (Chinese Letter-Number Span). When independent neurocognitive tests were analyzed, there were significant age differences in the WCST (perseverative errors and category completed, p=0.025, 0.023) and the SET (raw score, p=0.050). The older age group tended to do worse in the total profile score of the SET and correct responses of the HSC Part A. However, when these tests were grouped into specific executive function components, a significant difference was found between the two groups in attention allocation and planning (p=0.007) and total component score (p=0.026). Regression analyses also indicated that age accounted for only very little variance of executive function in this narrow band of the elderly, whereas educational level accounted for a large part of the variance in initiation (R(2)=0.252, p<0.001), switching and flexibility (R(2)=0.211, p<0.001), and updating (R(2)=0.236, p<0.001) components of executive function. Our findings suggest that a significant decline in general executive functioning with advancing age was only evident in some putative tests in this sample. In addition, executive functions were selectively affected by older age, with attention location and planning and initiation being the components that were most affected.     

Ecological validity of neuropsychological tests: focus on the California Verbal Learning Test and the Wisconsin Card Sorting Test.

To date, few studies have assessed the ecological validity of current measures of memory and executive functioning, particularly the California Verbal Learning Test (CVLT) and the Wisconsin Card Sorting Test (WCST). A battery of tests, including the CVLT and the WCST, was administered to 28 severely head-injured adults who were 1 year or more postinjury. Hierarchical linear regression was performed to assess the relationship between these cognitive tests and work functioning while statistically controlling for physical disability, emotional distress, and memory compensation strategies utilized by the participants. Results suggest that the CVLT was best at predicting performance on the job; however, the CVLT and the WCST were about equally predictive of the type of position held by a participant. Hence, this study demonstrates the ecological validity of measures of memory and executive functioning for predicting work-related skills.     

Age-group differences in set-switching and set-maintenance on the Wisconsin Card Sorting Task

This study examined developmental change in set-switching and set-maintenance on the Wisconsin Card Sorting Task (WCST), and sought to determine how executive function (EF) components (i.e., Working Memory, Shifting and Inhibition) may contribute to the observed changes on WCST performance. To this end, performance in four age groups (7-year-olds, 11-year-olds, 15-year-olds, and 21-year-olds) was measured on the WCST, and on three EF tasks assumed to tap Working Memory, Shifting, and Inhibition. The results showed that adult levels of performance were reached in 11-year-olds for set-switching, and in 15-year-olds for set-maintenance. A subsequent principal component analysis revealed that set-switching and set-maintenance loaded on two factors for 7-year-olds, but a single factor in the other age groups. Finally, regression analyses yielded a complex pattern of results concerning the prediction of set-switching and set-maintenance by the performance on tasks used to assess the EF components. The results were interpreted to suggest distinct developmental trends in set-switching and set-maintenance abilities required by the WCST.     

Age-Group Differences in Set-Switching and Set-Maintenance on the Wisconsin Card Sorting Task

This study examined developmental change in set-switching and set-maintenance on the Wisconsin Card Sorting Task (WCST), and sought to determine how executive function (EF) components (i.e., Working Memory, Shifting and Inhibition) may contribute to the observed changes on WCST performance. To this end, performance in four age groups (7-year-olds, 11-year-olds, 15-year-olds, and 21-year-olds) was measured on the WCST, and on three EF tasks assumed to tap Working Memory, Shifting, and Inhibition. The results showed that adult levels of performance were reached in 11-year-olds for set-switching, and in 15-year-olds for set-maintenance. A subsequent principal component analysis revealed that set-switching and set-maintenance loaded on two factors for 7-year-olds, but a single factor in the other age groups. Finally, regression analyses yielded a complex pattern of results concerning the prediction of set-switching and set-maintenance by the performance on tasks used to assess the EF components. The results were interpreted to suggest distinct developmental trends in set-switching and set-maintenance abilities required by the WCST.     

Anodal tDCS of dorsolateral prefontal cortex during an Implicit Association Test

Anodal stimulation of dorsolateral prefrontal cortex by transcranial Direct Current Stimulation (tDCS) has been shown to enhance performance on working memory tasks. However, it is not yet known precisely which aspects of working memory – a broad theoretical concept including short-term memory and various executive functions – are involved in such effects. In the current study, we aimed to determine whether tDCS would reduce bias effects on an Implicit Association Test, in which subjects must respond either congruently or incongruently to pre-existing evaluative associations. Such biases reflect a conflict between automatic associations and executive function, and tDCS was hypothesized to cause a shift in this balance in favor of executive function. The results clearly contradicted this hypothesis: tDCS did improve reaction times, but in the congruent rather than incongruent mapping condition. We conclude that DLPFC tDCS does not directly improve the ability to overcome bias; previous findings concerning working memory enhancement appear to reflect effects on a different component of executive function.     

A psychometric analysis of the California Card Sorting Test.

The purpose of this study is to begin to characterize performance on the California Card Sorting Test (CCST), a relatively new measure of executive function specifically designed to fractionate problem-solving ability into its cognitive components. Data describing the performance of 135 neurologically intact young adults on the CCST and four other common measures of executive function are presented. Factor analyses indicated that the CCST is a valid measure of concept formation and abstract ability and that the CCST taps abilities different from those measured by commonly used tests of executive function. While further work must be done, the CCST seems to hold promise as a neuropsychological assessment instrument.     

Wisconsin Card Sorting Test performance in above average and superior school children: relationship to intelligence and age.

This study explores the relationship of intelligence and age to scores on the Wisconsin Card Sorting Test, a measure of executive function. A sample of 26 normal children with Wechsler Intelligence Scale for Children-III (WISC-III) Full-Scale IQS above 130 and 24 normal children with WISC-III Full-Scale IQS between 110 and 129 were administered the test. A comparison to published norms revealed that above average children outperformed the average 9- to 14-year-old child on every measure at every age. Multiple regression analyses statistically related the Wisconsin Card Sorting Test, perseverative, nonperseverative, total errors, and trials to the first category of intelligence. Intelligence proved to be a significant qualifier of age trends. Gender relationships were nonsignificant in a preliminary analysis.     

Executive dysfunction and memory in older patients with major and minor depression.

Executive function, known to be impaired during late-life depression, is dependent on frontostriatal pathways. Memory is also frequently observed to be impaired among late-life depressed patients, so we assessed the possibility that executive function mediates the learning and recall deficit as a "downstream" effect of the frontostriatal compromise in executive function. A cross-sectional sample of minor and major depressed patients (N = 95) and nondepressed volunteers (N = 71), screened for other Axis I disorders, dementia, medical comorbidity and severity of depression, completed a neuropsychological battery that included the California Verbal Learning Test (CVLT) and other tests selected for convergent and divergent validity testing. Depressed patients differed from controls on learning the word list and on related and unrelated executive tasks. Executive function was a mediator for depressed patients verbal learning scores (z = -2.67, p = .01). A nonverbal executive score also mediated verbal learning (z = -2.18, p = .03) indicating convergent validity of executive dysfunction during verbal learning exercises. In conclusion, the verbal memory deficits typically attributed to late-life depression may result from impaired executive functioning during the learning phase of the recall task.     

Acute effects of moderate aerobic exercise on specific aspects of executive function in different age and fitness groups: A meta‐analysis

Whereas a wealth of studies have investigated acute effects of moderate aerobic exercise on executive function, the roles of age, fitness, and the component of executive function in this relationship still remain unclear. Therefore, the present meta‐analysis investigates exercise‐induced benefits on specific aspects of executive function in different age and aerobic fitness subgroups. Based on data from 40 experimental studies, a small effect of aerobic exercise on time‐dependent measures (g = .35) and accuracy (g = .22) in executive function tasks was confirmed. The results further suggest that preadolescent children (g = .54) and older adults (g = .67) compared to other age groups benefit more from aerobic exercise when reaction time is considered as dependent variable. In contrast to age, aerobic fitness and the executive function component had no influence on the obtained effect sizes. Consequently, high aerobic fitness is no prerequisite for temporary improvements of the executive control system, and low‐ as well as high‐fit individuals seem to benefit from exercise in a similar way. However, a higher sensitivity of executive function to acute aerobic exercise was found in individuals undergoing developmental changes. Therefore, preadolescent children and older adults in particular might strategically use a single aerobic exercise session to prepare for a situation demanding high executive control.     

Executive dysfunction and memory in older patients with major and minor depression.

Executive function, known to be impaired during late-life depression, is dependent on frontostriatal pathways. Memory is also frequently observed to be impaired among late-life depressed patients, so we assessed the possibility that executive function mediates the learning and recall deficit as a "downstream" effect of the frontostriatal compromise in executive function. A cross-sectional sample of minor and major depressed patients (N=95) and nondepressed volunteers (N=71), screened for other Axis I disorders, dementia, medical comorbidity, and severity of depression, completed a neuropsychological battery that included the California Verbal Learning Test and other tests selected for convergent and divergent validity testing. Depressed patients differed from controls on learning the word list and on verbal and nonverbal executive tasks. Executive function was a mediator for depressed patients verbal learning scores (z=-2.67, p=.01). A nonverbal executive score also mediated verbal learning (z=-2.18, p=.03) indicating convergent validity of executive dysfunction during verbal learning exercises. In conclusion, the verbal memory deficits typically attributed to late-life depression may result from impaired executive functioning during the learning phase of the recall task.