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Executive function deficits in early Alzheimer's disease and their relations with episodic memory.

Previous research suggests that patients with Alzheimer's disease (AD) are impaired on executive function early in the course of disease, but negative findings were reported. To evaluate the performance on executive tasks in early AD and to determine the involvement of memory on the outcome of executive tasks. Thirty-six AD patients were divided into two subgroups on the basis of the MMSE: very mild and mild. The comparison with 17 normal controls shows that very mild AD patients had deficits on visuospatial short-term memory, episodic memory, flexibility and self-monitoring abilities, concept formation and reasoning. The mild AD patients showed additional deficits on the Similarities test. Episodic memory and executive deficits occur in the very early stage of AD and precede impairment in constructional praxis, language and sustained attention. With the progression of the disease, additional deficit is observed in abstract thinking. In mild AD, memory failure is also related to executive impairment.

Aged↗

Effects of past noninjection drug abuse upon executive function and working memory in HIV infection.

Interactive effects of past noninjection drug abuse/dependence and HIV disease status upon measures of executive function were assessed in a group of 294 homosexual men. Participants were stratified according to HIV status and substance use diagnoses, thereby yielding a 4 (seronegative, asymptomatic seropositive, symptomatic seropositive, and AIDS defining illness) x 2 (never abused drugs, previous substance use disorder) design. Significant main effects of HIV status were found on the Wisconsin Card Sorting Test, Ruff Figural Fluency Test, Trail Making Test B, and total number of impaired performances. Analyses revealed that men with AIDS defining illness performed worse than the other three groups. Drug use history had no significant effect upon neurobehavioral function, and effect sizes for drug abuse history were small. The data suggest that prior drug use yields little if any residual cognitive impairment in HIV infection.

Acquired Immunodeficiency Syndrome↗

Performance on measures of executive function following pediatric traumatic brain injury.

OBJECTIVE: To investigate the relationships among age at injury, neuroanatomic lesion location, and measures of executive function (EF) following paediatric traumatic brain injury (TBI). METHODS: EF was assessed in 68 children (aged 7-15) with moderate-to-severe TBI 1 year post-injury. EF tests included: (1) Tower of Hanoi (TOH), a measure of problem solving ability, (2) Wisconsin Card Sorting Test (WCST), a measure of categorization and ability to shift cognitive strategies, (3) Letter Fluency (LF), a measure of novel lexical search and rule-governed word generation. EF variables included number of moves needed to achieve a 3-ring solution on the TOH, number of perseverative and non-perseverative errors on the WCST, and number of words generated on LF. Intellectual functioning was also assessed using the Verbal Intellectual Quotient (VIQ) from the Wechsler Intelligence Scale from Children-3rd edn (WISC-III). Data from standardized MRIs, performed at 3-months post-injury, were available for all subjects and were used to determine lesion location, lesion volumes, and total number of lesions. The relationships among EF, lesion variables (frontal lesion volume, extrafrontal lesion volume, total number of lesions) and age at injury were examined. Pre-injury special education services and attention deficit hyperactivity disorder (ADHD) were controlled for. RESULTS: Younger age at injury was associated with more perseverative errors on the WCST and worse performance on LF. Frontal lesion volume was not predictive of performance on any measures of EF. Greater extrafrontal lesion volume and total number of lesions were predictive of worse performance on LF. When controlling for pre-injury special education placement and pre-injury ADHD, there was little change in the results. CONCLUSIONS: Younger age at injury places children at greater risk of impairment on measures of EF. Performance on measures of EF depends on brain variables other than frontal lobes including extrafrontal cortical brain areas and total number of lesions. The relationship between extrafrontal brain regions and EF suggests that domain-specific cognitive content (i.e. language or visuospatial analysis), mediated by the parietal or temporal lobes, may disrupt underlying cognitive processes necessary for successful performance on measures of EF. In addition, the association between total number of lesions and EF may be related to disconnections and disruption of frontal/subcortical systems.

Adolescent↗

A Canadian multicenter trial assessing memory and executive functions in patients with schizophrenia spectrum disorders treated with olanzapine.

Serial verbal learning task (explicit long-term memory) and verbal fluency (generation of a response) are tests that are usually severely impaired in schizophrenia. Despite the growing literature supporting the clinical efficacy of olanzapine, psychiatrists still question its cognitive consequences. This study assessed the efficacy of olanzapine on neurocognitive functioning. Patients (N = 134) meeting diagnostic criteria for schizophrenia, schizophreniform, or schizoaffective disorders began an 8-week, open-label olanzapine treatment at a dose of 5 mg/d, which was increased to 10 mg/d after 1 week. Daily dosage was subsequently adjusted between 5 and 20 mg/d based on individual clinical status. All previous antipsychotics were tapered and discontinued during the first 2 weeks of the study. Neuropsychologic assessments were carried out at baseline and at 4 and 8 weeks. Explicit long-term memory was assessed with the Rey Auditory-Verbal Learning Test: the average immediate recall score significantly improved (P < 0.001), as did the delayed recall score (P < 0.001). The average total score on category fluency improved from 34.6 words at baseline to 37.6 words at end point (P < 0.0001). Time on both Trail A and B making tasks significantly decreased (P < 0.0001). Lack of a control arm makes it impossible to exclude a practice effect as an explanation for the enhanced cognitive performance, although the Word List Recall test represents one of the better resources to avoid a practice effect. After switching to olanzapine, there was a statistically significant improvement of cognitive function in the 3 main domains tested and no significant worsening of any memory or executive function measure.

Acoustic Stimulation↗

Lack of influence of COMT and NET genes variants on executive functions in schizophrenic and bipolar patients, their first-degree relatives and controls.

Abnormal dopaminergic function in the prefrontal cortex (PFC) may be a key factor in the etiopathogeny of schizophrenia and bipolar disorder. Both schizophrenic and bipolar subjects have executive functions (EF) deficits, thought to reflect abnormal PFC function. The main inactivation pathways for dopamine in the PFC are enzymatic cleavage by the Carboxy-O-Methyl-Transferase (COMT) and reuptake by the nor-epinephrine transporter (NET). Our aim in this study was to replicate previous studies that investigated influence of the COMT genotype on EF in schizophrenic subjects, their relatives and controls and extend their scope by including bipolar patients, and their relatives and by exploring NET gene polymorphisms influence on executive performances. We investigated one functional polymorphism of the COMT gene and two polymorphisms of the NET gene. EF were assessed by means of the Trail Making Test (TMT) and the Wisconsin Card Sorting Test (WCST). We assessed the effect of each of the three genotypes on EF for the whole sample (N = 318) and separately in schizophrenic (N = 66), bipolar (N = 94) and healthy subjects (i.e., relatives and controls N = 158). Separate analyses were performed because of the presence, in patients samples, of potentially confounding factors, especially medication. Genotype had no significant effect on the cognitive measures in any of the analyses (for the two EF measures, the three polymorphisms, and the four groups). In our sample we found no evidence in favor of a major effect of COMT or NET polymorphisms on the two tests of EF.

Adult↗

Relationships between neuropsychological measures of executive function and behavioral measures of ADHD symptoms and comorbid behavior.

OBJECTIVE: The aim of this study was to examine the relationship between executive functions (EFs), as measured by neuropsychological tests, and symptoms of attention deficit hyperactivity disorder (ADHD) and comorbid behavior, as rated by parents and teachers. As intelligence and language ability are important covariates they were also assessed. METHOD: The sample consisted of 43 children aged 7-11 years who were referred for neuropsychological assessment at a tertiary clinical facility. Most of the children had the diagnosis of ADHD combined or inattentive type. Different aspects of EFs were assessed. RESULTS: EFs were not significantly related to symptoms of ADHD, but only to comorbid symptoms of depression and autistic symptomatology. Language ability rather than EFs best predicted teacher ratings of inattention. CONCLUSIONS: The results of the study do not support the EF theory of ADHD. The importance of screening for comorbid language disorders in children referred for ADHD is emphasized.

Attention Deficit Disorder with Hyperactivity↗

Executive function abilities in autism and Tourette syndrome: an information processing approach.

This study used information processing paradigms to provide a detailed examination of executive function abilities in autism. The performance of non-retarded autistic children was compared with that of two matched control groups, one with Tourette Syndrome and the other developmentally normal. Autistic subjects performed as well as controls on tasks requiring global-local processing and inhibition of neutral responses. In contrast to both control groups, however, the autistic sample was significantly impaired on a measure of cognitive flexibility. The performance of children with Tourette Syndrome did not differ from that of normal controls on any task. These results refine our knowledge about executive dysfunction in autism and suggest a new conceptual framework and general method for investigating the cognitive underpinnings of neurodevelopmental disorders.

Adolescent↗

Which executive functioning deficits are associated with AD/HD, ODD/CD and comorbid AD/HD+ODD/CD?

This study investigated (1) whether attention deficit/hyperactivity disorder (AD/HD) is associated with executive functioning (EF) deficits while controlling for oppositional defiant disorder/conduct disorder (ODD/CD), (2) whether ODD/CD is associated with EF deficits while controlling for AD/HD, and (3) whether a combination of AD/HD and ODD/CD is associated with EF deficits (and the possibility that there is no association between EF deficits and AD/HD or ODD/CD in isolation). Subjects were 99 children ages 6-12 years. Three putative domains of EF were investigated using well-validated tests: verbal fluency, working memory, and planning. Independent of ODD/CD, AD/HD was associated with deficits in planning and working memory, but not in verbal fluency. Only teacher rated AD/HD, but not parent rated AD/HD, significantly contributed to the prediction of EF task performance. No EF deficits were associated with ODD/CD. The presence of comorbid AD/HD accounts for the EF deficits in children with comorbid AD/HD+ODD/CD. These results suggest that EF deficits are unique to AD/HD and support the model proposed by R. A. Barkley (1997).

Adolescent↗

Executive functioning and memory for the Rey-Osterreith complex figure task among community adolescents.

Although there is empirical support for the link between executive functioning (EF) and visual memory among adults, there has been less exploration of this link among children, especially adolescents. We examined the relation between several EF measures and performance on the Rey-Osterrieth Complex Figure (RCF) in a sample of 160 community adolescents. Each was administered the Wisconsin Card Sorting Test (WCST), Conners Continuous Performance Test (CPT), and the RCF, scored using Bernstein and Waber's (1996) Developmental Scoring System (DSS). Ability to organize the RCF related to memory encoding/retrieval, but not to long-term storage. Indexes derived from the WCST and CPT failed to correlate with any RCF index, raising questions about the relation between DSS scores and EF. Even so, data supported the convergent validity of the DSS system as a reflection of visual-constructional ability and provided evidence of the importance of organizational strategies to visual memory among adolescents.

Adolescent↗

The ecological validity of tests of executive function.

Ninety-two mixed etiology neurological patients and 216 control participants were assessed on a range of neuropsychological tests, including 10 neuropsychological measures of executive function derived from 6 different tests. People who knew the patients well (relatives or carers) completed a questionnaire about the patient's dysexecutive problems in everyday life, and this paper reports the extent to which the tests predicted the patients' everyday life problems. All of the tests were significantly predictive of at least some of the behavioral and cognitive deficits reported by patients' carers. However, factor analysis of the patients' dysexecutive symptoms suggested a fractionation of the dysexecutive syndrome, with neuropsychological tests loading differentially on 3 underlying cognitive factors (Inhibition, Intentionality, and Executive Memory), supporting the conclusions that different tests measure different cognitive processes, and that there may be limits to the fractionation of the executive system.

Adult↗

Neurobiology of executive functions: catecholamine influences on prefrontal cortical functions.

The prefrontal cortex guides behaviors, thoughts, and feelings using representational knowledge, i.e., working memory. These fundamental cognitive abilities subserve the so-called executive functions: the ability to inhibit inappropriate behaviors and thoughts, regulate our attention, monitor our actions, and plan and organize for the future. Neuropsychological and imaging studies indicate that these prefrontal cortex functions are weaker in patients with attention-deficit/hyperactivity disorder and contribute substantially to attention-deficit/hyperactivity disorder symptomology. Research in animals indicates that the prefrontal cortex is very sensitive to its neurochemical environment and that small changes in catecholamine modulation of prefrontal cortex cells can have profound effects on the ability of the prefrontal cortex to guide behavior. Optimal levels of norepinephrine acting at postsynaptic alpha-2A-adrenoceptors and dopamine acting at D1 receptors are essential to prefrontal cortex function. Blockade of norepinephrine alpha-2-adrenoceptors in prefrontal cortex markedly impairs prefrontal cortex function and mimics most of the symptoms of attention-deficit/hyperactivity disorder, including impulsivity and locomotor hyperactivity. Conversely, stimulation of alpha-2-adrenoceptors in prefrontal cortex strengthens prefrontal cortex regulation of behavior and reduces distractibility. Most effective treatments for attention-deficit/hyperactivity disorder facilitate catecholamine transmission and likely have their therapeutic actions by optimizing catecholamine actions in prefrontal cortex.

Adamantane↗

Executive functions and rehabilitation of the integrated self: a commentary on Ylvisaker and Feeney.

This commentary is a response to Ylvisaker and Feeney's paper "Executive functions, self-regulation and learned optimism in paediatric rehabilitation: a review and suggestions for intervention". Drawing on a diverse literature, the authors provide a broad empirical basis for a pragmatic approach to rehabilitation for children. Their contribution is critically reviewed in terms of the validity of their central thesis and the likely impact of their proposals. Although theoretically ambiguous in places and lacking the benefit of a truly developmental framework for intervention, their proposals, nevertheless, represent a coherent heuristic framework for teachers, clinicians and parents that has corollary implications for how paediatric rehabilitation is funded.

Child↗

Executive functioning, temperament, and drug use involvement in adolescent females with a substance use disorder.

BACKGROUND: This study determined whether temperament mediates the relation between executive functioning (EF) and drug use involvement and whether EF and temperament interact to account for unique variance in drug use involvement. METHOD: Participants were 340, 14-18-year-old, adolescent females with a substance use disorder and controls. EF was measured using a battery of neuropsychological tests, temperament was assessed using the Dimensions of Temperament Survey--Revised, and drug use involvement was measured with the Drug Use Screening Inventory. RESULTS: Temperament mediated the relation between EF and drug use involvement. Girls with a 'difficult' temperament exhibited significantly greater drug use involvement than girls with a 'good' temperament. Finally, low EF was significantly related to increased drug use involvement for girls with a good temperament, but not for girls with a difficult temperament. CONCLUSIONS: The results suggest that a difficult temperament is a more important risk factor for drug use than low EF. Given previous studies that have shown significant relations between EF and drug use, further research on this topic is warranted.

Adolescent↗

Is impaired executive function a single or multidimensional disability?

This study was undertaken to determine if certain logical relations might be found in two pairs of similar executive functioning tasks: (a) Design Fluency and Word Fluency, and (b) the Tinker Toy and Story Telling Tests. Overall, the results were "inconsistent," with there being no meaningful relations found between tests with regard to similarities in task demand, theoretical hierarchical relations, or whether the tasks were verbal or nonverbal (with the exception of a very close relation between Design Fluency and Tinker Toy Test.). Despite the apparent entropy of the findings, they have substantial clinical and theoretical importance given the simultaneously rigid and weak-minded definitions and measures of disexecutive disability in current use.

Adult↗

Heritability and the comorbidity of attention deficit hyperactivity disorder with behavioral disorders and executive function deficits: a preliminary investigation.

The heritability and comorbidity of attention deficit hyperactivity disorder (ADHD) with conduct disorder (CD), oppositional defiant disorder (ODD), and executive function (EF) deficits were examined in 224 child twins (140 monozygotic and 84 dizygotic). The Coolidge Personality and Neuropsychological Inventory for Children (Coolidge, 1998), a standardized, 200-item, Diagnostic and Statistical Manual of Mental Disorders (4th ed.; American Psychiatric Association, 1994) aligned, parent-as-respondent inventory, assessed psychopathology. Structural equation model fitting revealed that the individual scale heritabilities were substantial: .82 for ADHD, .74 for CD, .61 for ODD, and .77 for EF deficits. The results of the multivariate twin analyses suggest that ADHD shares most of its genetic liability with CD, ODD, and EF deficits. Thus, the findings argue for a common biological risk underlying these commonly comorbid externalizing behavior problems and cognitive deficits. The residual genetic variance provides preliminary support for additional genetic influences underlying CD, ODD, and EF that are independent of ADHD.

Adult↗

Executive functioning, attention and frontal lesions in patients with chronic CHI.

To study the presence and nature of dysexecutive problems after CHI, a series of unstructured tasks tapping executive functioning were selected. These were administered to a group of 51 participants with CHI in the chronic stage (i.e. several years post-injury) and to 45 healthy controls. In addition, well-known structured tests of attention and planning were administered. Of the executive tasks, only the Executive Route Finding task showed a significant difference between both groups. A multivariate analysis on the attention tests showed a significant difference between groups, indicating that patients in the chronic stage still process information slower than controls. Within the patient group, patients with and without frontal focal lesions were also compared on executive and attention tests. No differences were found with respect to the latter. However, patients with frontal lesions performed worse on a measure of the Executive Route Finding task. It is concluded that patients with CHI, especially when they have frontal damage, have to rely more heavily on externally provided cues, but this dysexecutive problem can only be demonstrated in tasks that resemble daily life tasks by providing very little structure.

Adolescent↗

The relationship between executive function and verbal memory in Parkinson's disease.

A growing body of evidence suggests that the various cognitive symptoms found in Parkinson's disease (PD) are secondary to executive dysfunction. Studies addressing this possibility for memory impairment specifically have not included measures of working memory nor have they ruled-out potential mediating variables such as overall level of cognitive impairment or depression. The purpose of this study was to include measures of these variables in determining the relationship between multiple aspects of executive function and delayed verbal recall in 32 idiopathic PD patients. Results were consistent with the original hypothesis and further suggest that working memory is a key factor in recall memory and may mediate the relationship between other executive measures and recall in PD.

Cognition Disorders↗

Are central executive functions working in patients with focal frontal lesions?

The aim of this study was to examine the hypothesis of a link between frontal cortex and two executive functions in working memory: the capacity to perform a dual task and the ability to inhibit irrelevant information. A dual task designed to assess the capacity to perform storage and processing simultaneously and a directed forgetting task designed to assess the capacity to actively inhibit no-longer relevant information were administered to a group of patients with focal frontal lesions and to a group of control participants. The results revealed that despite showing reduced short-term storage, frontal patients performed the dual task and inhibited the no-longer relevant information as well as control participants. These findings suggest that not all-executive processes are exclusively sustained by the frontal cortex [Quart J Exp Psychol 9 (1996) 5; Curr Opin Neurobiol 10 (2000) 195; Neuropsychology (1994) 544; The Cognitive Neuropsychology of Alzheimer-type dementia. Oxford, New York: Oxford University Press, 1996].

Adult↗