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PubMed2003

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↗

PubMed2002

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↗

PubMed2003

Psychometrically matched measures of global cognition, memory, and executive function for assessment of cognitive decline in older persons.

Item response theory methods were used to derive psychometrically sophisticated measures of global cognition, memory, and executive function. Goals were that these measures (a) could be derived from commonly used neuropsychological tests, (b) would have linear measurement properties, and (c) would be psychometrically matched. Scale development was based on a sample of 400 older individuals with cognitive function ranging from normal to demented. Scales were reasonably matched with linear measurement over an ability range relevant to many important clinical applications. Cognitively normal, mild impairment, and dementia participant groups differed on baseline measures and rate of decline. Association of measures with quantitative structural magnetic resonance imaging variables followed expected patterns. This approach to scale development may have applications for other neuropsychological assessment problems.

Aged↗

PubMed1998

The Tower of London(DX): a standardized approach to assessing executive functioning in children.

In the current study, the Tower of London (Shallice, 1982) was modified to enhance its clinical utility as a measure of childhood executive functioning. The Tower of London-Drexel (TOL(DX)) was administered to normal control (NC; N = 56) and attention-deficit hyperactivity disorder (ADHD; N = 99) children (ages 7 to 12) to determine whether age-related changes in performance were evident, to gather normative data, and to evaluate the test-retest reliability and criterion-validity of the measure. The results revealed age-related changes in score performance, age-group normative data, an acceptable level of reliability and significant differences in performance of NC and ADHD subjects. Further, discriminant analysis classification rates determined that the TOL(DX) was sensitive and highly specific to ADHD. Implications and limitations of the study are discussed.

Journal Article↗

PubMedDate not supplied

Prospective memory and executive function in schizophrenia.

Experimental studies of normal subjects have shown that the intention to perform an action speeds word recognition for items related to that intention (Goschke & Kuhl, 1993). This phenomenon--the intention superiority effect (ISE)--is thought to be mediated by frontal executive functions. Since schizophrenia is characteristically associated with forms of frontal-executive dysfunction, an impaired ISE might be expected in this patient group. A script-learning paradigm was used to investigate the ISE in 10 schizophrenics who do show evidence of executive dysfunction and in 10 who do not. As predicted, only the former showed an ISE; however, all schizophrenics showed an ISE to words semantically related to the intention. It seems that the ability to form specific intentions is impaired only in schizophrenics with executive dysfunction; however, they retain the ability to form more generalized intentions.

Adult↗

PubMed1997

Executive function and uptake of 99mTc-exametazime shown by single photon emission tomography after oral idazoxan in probable Alzheimer-type dementia.

Preliminary reports suggest improved executive function in patients with lobar dementia after treatment with single doses of the alpha 2 adrenoceptor antagonist, idazoxan. The potential for use in probable Alzheimer-type dementia prompted the present study. Fifteen patients with probable Alzheimer-type dementia were examined twice with neuropsychological measures and 14 also with single photon emission tomography (SPET) after a single double blind oral administration of 40 mg idazoxan or placebo in a balanced cross-over design. Brain perfusion maps were spatially transformed into standard stereotactic space and compared pixel-by-pixel. A parametric analysis was used to examine the relationship between the drug effect, verbal fluency and brain perfusion. Two to 3 h after idazoxan, measures of reaction time, Stroop test, category fluency and anxiety were unchanged. Verbal fluency (letter) and spatial working memory were impaired and performance on the Tower of London test in a sub-set of patients showed a trend to impairment in the idazoxan condition. Idazoxan produced a modest relative activation in left thalamus and inferior occipital cortex: decreases occurred in inferior anterior cingulate and left insular cortex. There were significant correlations on both days between measures of fluency and brain perfusion in left lateral prefrontal cortex. The reduced performance with idazoxan was directly correlated with reduced perfusion in left lateral prefrontal cortex, supporting an important interaction between drug and task performance. The imaging component of the study therefore suggested that activation of frontal networks is necessary for performing fluency tasks in Alzheimer-type dementia. Brain networks involving prefrontal cortex are the locus for the primary cognitive effects of noradrenergic drugs. The direction of the effect of any dose of agonist or antagonist may depend critically upon the age and pathology of the experimental subjects and the relationship between performance, noradrenergic drive and task difficulty.

Adrenergic alpha-Antagonists↗

PubMed2003

Task-set switching deficits in early-stage Huntington's disease: implications for basal ganglia function.

Executive functions are likely mediated by interconnected circuits including frontal lobe and basal ganglia structures. We assessed the executive function of task switching in patients with early-stage Huntington's disease (HD), a neurodegenerative disease affecting the basal ganglia. In two experiments, the HD patients had greater difficulty when switching than when repeating a task than matched controls, and this was true even when scaling for the overall slowing of the patients. In the first experiment, HD patients had a switching deficit even in a "pure" condition where they had to switch, predictably, and with substantial preparation time, between stimuli having only one possible response, indicating a switching deficit different from that for patients with Parkinson's disease or frontal lobe trauma, and possibly relating to inadequate activation of stimulus-response links or "response set." In the more elaborate second experiment, we could not account for the switching deficit of the patients in terms of inadequate preparation in advance of a switch, deficient suppression of task-set processing from the preswitch trial, or impaired suppression of interference due to the presence of a competing task set. Instead, we found that part of the switching deficit was due to elevated reaction time and errors on switch trials for a repeated response (same button press as on preswitch trial) relative to an alternated response (different button press from preswitch trial). We argue that this elevated "repetition effect" for the HD patients is due to excessive inhibition of the just-performed response in advance of a switch. Alterations in the "response-setting" process alone (Experiment 1) and both the response-setting and "response inhibition" process (Experiment 2) probably arise from striatal pathology in HD, thus accounting for the task-switching deficits and showing how basal ganglia implemented response processes may underpin executive function.

Adult↗

PubMed1999

Executive function in depression: the role of performance strategies in aiding depressed and non-depressed participants.

OBJECTIVES: Depression has been found to be associated with dysfunction in executive processes, whereas relatively automatic processes are thought to remain intact. Failure to generate or implement adequate performance strategies has been postulated in depressed participants. The present study investigated spontaneous strategy usage in depressed and control participants, and the effectiveness of providing a hint about performance strategies. METHODS: Unipolar depressed participants were compared with matched healthy controls on three tasks sensitive to executive function: memory for categorised words, response suppression, and multiple scheduling. Participants in each group were randomly allocated to strategy aid and no strategy aid conditions. Those in the strategy aid condition were given a hint about the use of an appropriate performance strategy for each task, in addition to the standard instructions given to those in the no strategy aid condition. RESULTS: Depressed participants performed worse than controls on each of the three tasks, and were found to use appropriate performance strategies less often. Provision of strategy hints increased the use of performance strategies in two of the three tasks, memory for categorised words, and response suppression, but did not significantly improve overall performance for either group. CONCLUSIONS: The findings were consistent with the view that depressed participants fail to use appropriate performance strategies spontaneously to the same extent as controls. However, provision of information alone does not seem to be an adequate means of enhancing performance. The role of performance strategies in cognitive impairment in depression is discussed, both in terms of initiating use of such strategies and carrying these out efficiently.

Adult↗

PubMed2003

Switching attention and resolving interference: fMRI measures of executive functions.

Is there a single executive process or are there multiple executive processes that work together towards the same goal in some task? In these experiments, we use counter switching and response inhibition tasks to examine the neural underpinnings of two cognitive processes that have often been identified as potential executive processes: the switching of attention between tasks, and the resolution of interference between competing task responses. Using functional magnetic resonance imaging (fMRI), for both event-related and blocked design tasks, we find evidence for common neural areas across both tasks in bilateral parietal cortex (BA 40), left dorsolateral prefrontal cortex (DLPFC; BA 9), premotor cortex (BA 6) and medial frontal cortex (BA 6/32). However, we also find areas preferentially involved in the switching of attention between mental counts (BA 7, BA 18) and the inhibition of a prepotent motor response (BA 6, BA 10), respectively. These findings provide evidence for the separability of cognitive processes underlying executive control.

Adolescent↗

PubMed1995

Executive functions of the frontal lobes: psychometric properties of a self-rating scale.

This study investigated the psychometric properties of a self-rating scale designed to test the executive functions of the frontal lobes. A set of 16 items was selected, based on face validity, from the 200-item Coolidge Axis II Inventory. Cronbach scale reliability for the new scale was .72 on 1,223 purportedly normal participants. A factor analysis yielded a three-factor structure, Decision-making difficulties (8 items, 23% of the variance, scale reliability .77), Poor planning (4 items, 15% of the variance, scale reliability .63), and Task incompletion (6 items, 9% of the variance, scale reliability .66). A multivariate analysis of variance, performed on the overall scale sum and the three subscales, between 17 closed head-injured patients and a matched control group was significant. The head-injured patients scored significantly higher on the over-all measure of executive dysfunction and higher on the decision-making difficulties subscale but not on the other two subscales.

Adolescent↗

PubMed2001

Constructive thinking, executive functioning, antisocial behavior, and drug use involvement in adolescent females with a substance use disorder.

The main aim of this study was to determine how constructive thinking (CT), executive functioning (EF), and antisocial behavior (ASB) are related to drug use involvement in 282 adolescent females, 14-18 years of age, with a substance use disorder (SUD) and in controls. CT was measured using the Constructive Thinking Inventory (S. Epstein & P. Meier, 1989), EF was measured using a battery of neuropsychological tests, and ASB was measured using the Youth Self-Report Inventory (T. Achenbach, 1991) and a psychiatric interview. Females with an SUD demonstrated lower CT and EF scores and higher ASB scores compared with the controls. Low CT and low EF were significantly related to increased drug use involvement even when controlling for age, socioeconomic status, and vocabulary level. ASB partially mediated the relation between CT and drug use involvement, and it fully mediated the relation between EF and drug use involvement. Moreover, ASB moderated the relation between EF and drug use involvement.

Adolescent↗

PubMed2002

Effects of IQ on executive function measures in children with ADHD.

The present study compared children with Attention-Deficit Hyperactivity Disorder (ADHD) and controls on a selected set of clinical measures of executive function (EF). A total of 92 children (51 ADHD, 41 control), ages 6-16, completed measures chosen from a larger neuropsychological battery to illustrate diverse components of the EF construct (planning, inhibitory control, response preparation, memory search). The selected measures were moderately correlated with one another, and moderately correlated with IQ. After controlling for age, sex, presence of learning disability (LD), ADHD, and IQ test version, Full Scale IQ was significantly related to four of the five selected EF measures. A second analysis showed group differences on the EF measures at different IQ levels. After covarying for age, there was a significant multivariate effect for IQ level (average, high average, superior) and a significant multivariate interaction between group (ADHD vs. control) and IQ level. Three of the five selected EF measures showed significant univariate group effects (controls performing better than ADHD) at the average IQ level; however, there were no significant group differences between children with ADHD and controls at high average or superior IQ levels. These results suggest that clinical measures of EF may differ among children with ADHD and controls at average IQ levels, but there is poorer discriminatory power for these measures among children with above average IQ.

Adolescent↗

PubMed1999

Neuropsychological test performances of young depressed outpatient women. An examination of executive functions.

Thirty young, unmedicated, outpatient, depressed women were compared to an equal number of matching controls on a series of neuropsychological tests purported to be sensitive to the executive functions. Specifically, the measures included the Design Fluency Test, Hand Dynamometer tasks of grip strength, perseveration, and fatigue, the FAS Verbal Fluency Test, the Stroop Color and Word Test, and the Trail Making Test (Parts A and B). Despite past research which has indicated anterior hemispheric asymmetries and impaired neurocognitive performances in depressives, this research failed to identify any reliable differences between depressed and nondepressed women on any of the neuropsychological measures. These results argue against the frequently held stereotype that depressed individuals typically display impaired performances on neurocognitive tasks. Furthermore, since the profile of the depressed sample appeared to differ significantly from past studies, a discussion is provided as to how the characteristics of this group may have impacted the results. Implications of these findings for clinical practice and future research are also provided.

Journal Article↗

PubMed2003

Executive function, memory, and learning in Tourette's syndrome.

Young people with Tourette's syndrome (TS) alone, TS plus attention-deficit/hyperactivity disorder (+ADHD), or TS plus obsessive-compulsive disorder (+OCD) were compared with a healthy control group on a set of measures of executive functioning, memory, and learning. The TS-alone group was impaired on one executive measure involving inhibition and strategy generation but did not differ significantly from the healthy control group on other measures. The TS+ADHD group showed impairment on several executive measures. There was no evidence of impairment in implicit aspects of memory and learning for any of the TS groups. The findings are discussed in terms of the frontostriatal hypothesis of TS and the contribution of comorbid symptomatology.

Adolescent↗

PubMed1997

Executive function and psychosocial adjustment in children with early treated phenylketonuria: correlation with historical and concurrent phenylalanine levels.

The issue of what level of phenylalanine (phe) constitutes a safe upper limit for the therapeutic range in dietary treatment of phenylketonuria (PKU) remains unsettled. It has been proposed that the previous guideline figure of 600 mumol l-1 may result in specific impairment of executive functions such as attention, planning and set maintenance. The executive dysfunction theory was investigated by correlation historical and concurrent phe with executive, non-executive and personality tests in a group of early and continuously treated children, aged 10-13 years, with classical PKU, whose average phe levels of 355 mumol l-1 (SD = +/-144) for the pre-school period and 480 mumol l-1 (SD +/-193) for the primary school period corresponded to the upper limits presently recommended in the UK of 360 and 480 mumol l-1 for these age ranges. No clear associations were found between historical or concurrent phe levels and any of the neuropsychological or personality measures, thereby weakening the case for the emergence of executive deficits, at least when average phe levels remain close to the upper limits now considered safe. Furthermore no significant differences were found on psychological variables where comparison with population norms was possible.

Adjustment Disorders↗

PubMed1998

Factors affecting cognitive, motor, behavioral and executive functioning in children with phenylketonuria.

We administered measures of cognitive, frontal lobe (executive), behavioral and motor functioning to 18 children with classical phenylketonuria, aged 12-101 months, in order to determine the relationship of age, current and lifetime average phenylalanine levels, and individual variation (standard deviation of lifetime average levels) to these functions. On measures of cognitive function, in children > or = 3 y of age lower current phenylalanine levels were associated with higher cognitive functioning. On a behavioral temperament scale designed for normal children, we found that higher current and average phenylalanine levels correlated with more difficult temperament. Motor function was also poorer in children with phenylketonuria, and was most impaired in children with current phenylalanine levels >360 micromol/l. We also identified a previously unreported correlation between increased individual variation and poorer executive function performance, a finding that may raise new management concerns about level fluctuations. Maintenance of phenylalanine levels <360 micromol/l may be necessary for optimal performance in children with phenylketonuria.

Child↗

PubMed2002

Executive function deficits in patients with dementia of the Alzheimer's type: a study with a Tower of London task.

A growing number of studies report a deterioration of the executive function (EF) in dementia of the Alzheimer type (DAT). To evaluate EFs in DAT, a new version of the Tower of London (TOL) task, originally developed by Shallice (1982), was adapted. The new version of the test was built up in its easiest possible feature in order to be administrable to early- or middle-stage demented patients. Seventeen DAT patients, and 17 controls matched for age and sex, were administered the TOL. The protocol followed a "hierarchical paradigm," that is, simpler problems were embedded in more complex, subsequent problems. Results showed that DAT patients were impaired compared to controls. Both control and DAT groups showed a decrease in percentage of success rate in relation to the number of movements required by the task. On the more complex problems, the performance of DAT subjects was proportionally more impaired. Qualitative analysis revealed that rule breaking was a salient performance feature of the DAT group. These findings are consistent with the presence of an EF deficit in DAT.

Journal Article↗

PubMed1997

Memory and executive functions in amnesic and non-amnesic patients with aneurysms of the anterior communicating artery.

Ruptured and repaired anterior communicating artery (ACoA) aneurysm can result in devastating impairments involving memory, executive function, confabulation and personality change. Importantly, traditional cerebral areas implicated in amnesia are not damaged, yet amnesia can still be manifested. While ACoA patients show normal visual-constructional skills (i.e. copy scores) on the Rey-Osterrieth complex figure test, recall is often impaired. What is unclear is whether impaired recall is attributable to problems in encoding, accelerated rates of forgetting, retrieval or some combination. To disentangle these issues, we examined 10 patients with ruptured aneurysms of the ACoA, using the Rey-organizational and extended memory procedure which uses an organizational procedure for enhancing immediate recall and provides added sensitivity by combining recall with non-recall measures (e.g. recognition, spatial discrimination and spatial assembly). The major findings were: (i) immediate recall in amnesics was improved by providing an organizational strategy; (ii) following the organization trials, amnesics and non-amnesics retained information to a comparable extent over a 30-min delay; (iii) two subgroups of amnesics emerged, those subjects impaired in acquisition and a second group with impaired retrieval; (iv) all subjects showed preserved memory on non-recall measures. These findings have important implications with respect to using organizational strategies in cognitive treatments and in using non-recall measures in improving the validity and reliability of patient assessment.

Adult↗