Executive functioning as a potential mediator of age-related cognitive decline in normal adults

Critical requirements for the hypothesis that executive functioning is a potential mediator of age-related effects on cognitive functioning are that variables assumed to reflect executive functioning represent a distinct construct and that age-related effects on other types of cognitive functioning are reduced when measures of executive functioning are statistically controlled. These issues were investigated in a study involving 261 adults between 18 and 84 years of age. Although age-related effects on various cognitive abilities were substantially reduced after statistical control of the variance in measures hypothesized to represent executive functioning, there was only weak evidence for the existence of distinct constructs corresponding to executive functioning or to aspects of executive control concerned with inhibition, updating, or time sharing.     

Executive functioning as a mediator of the relationship between age and episodic memory in healthy aging

The extent to which age-related differences in executive functioning account for age-related differences in recall from episodic memory was examined in a group of healthy older adults. Fifty-one subjects between the ages of 60 and 91 years were given tests of general cognitive abilities, episodic memory, and executive functioning. A mediational model was proposed with executive functioning as the mediator of the relationship between age and delayed recall. Consistent with this model, regression analyses indicated that, when considered alone, age was a significant predictor of recall (p <.001); however, age was not a significant predictor of recall when the effect of executive functioning was partialled out of the equation (p=.37). Furthermore, the unique contribution of executive functioning accounted for 36% of the variance in recall performance. A significant portion of age-related differences in episodic memory recall, therefore, may be due to age-related differences in the executive skills required for optimal performance on such tests.     

Executive neurocognitive functioning and neurobehavioral systems indicators in borderline personality disorder: a preliminary study

It is argued that borderline personality disorder (BPD) represents the interaction of underlying neurobehavioral systems that are reflected principally in the phenotypic constructs of positive emotion, negative emotion, and nonaffective constraint (Depue & Lenzenweger, 2001). This preliminary and exploratory study sought to examine predictions made from the Depue-Lenzenweger model with respect to controlled (effortful) information processing in BPD. It was hypothesized that (a) BPD subjects may display deficits on tasks that require controlled information processing (sustained attention, spatial working memory, and executive functioning), (b) they may reveal elevated negative emotion as well as decreased positive emotion and nonaffective constraint, and (c) nonaffective constraint should be substantially inversely associated with accurate performance on controlled information processing tasks. The results of this study, which examined 24 BPD diagnosed individuals and 68 normal adults, found support for each of these predictions in relation to performance on the Wisconsin Card Sorting Test. The implications of these results for further experimental psychopathology investigations of BPD as well as further refinement of theoretical models of the disorder are discussed.     

Virtual action planning in Parkinson's disease: a control study.

Cognitive planning deficits affect patients with Parkinson's disease (PD) and traditional psychometric tests meet difficulties to evaluate their impact on daily life activities. Virtual reality (VR) may provide a new means of assessment. The objective of this study was firstly to develop a virtual environment (VE) useful to explore planning and secondly to examine the effectiveness of using VR in the assessment of cognitive planning for patients with PD. A virtual supermarket (VS) was designed in which participants carried out a task close to daily activities: a test of shopping list. There were two preliminary sessions to familiarize the participants with the software and the supermarket's layout. Then, during the assessment session, participants completed the task, without any time limitation. Global intellectual efficiency was assessed in order to exclude patients with dementia. Data related to the performance in the VS were recorded. Five patients with PD and five age-matched healthy volunteers, meeting inclusion criteria, constituted our convenience sample. The patients did not perform as well as the control group. In particular, the session's duration and the distance covered were longer. The patients' path is specific with numerous stops, turning around, and hesitancies. Finally, their motivation for further training sessions is aroused. The results underline the potential of using VR in the assessment of cognitive planning in PD. A larger analysis is currently being carried out to confirm and to explore all the outcome measures.     

Dopamine and cognitive functioning: brain imaging findings in Huntington's disease and normal aging

Recent brain imaging studies in Huntington's disease (HD) and normal aging suggest a relationship between central dopaminergic neurotransmission and cognitive performance. Results demonstrate substantial losses in dopamine (DA) function in both HD and aging. Moreover, HD patients and older adults show deficits across multiple cognitive domains, including episodic memory, speed of processing, and executive functioning. Although few studies are available at present, there is converging evidence that multiple measures of pre- and postsynaptic DA biochemistry are (a) highly interrelated, and (b) strongly associated with the cognitive deficits that accompany HD and aging. There is also emerging evidence that DA neurotransmission influences cognitive performance independent of HD or age. In general, the research reviewed in this article indicates that the nigrostriatal DA system is an important component of a frontostriatal circuitry that is critically involved in cognitive functioning.     

Executive functioning and positive psychological characteristics: a replication and extension

Positive psychological characteristics and executive function are correlated with gratitude, satisfaction with life, and forgiveness. The goal of this study was to replicate these findings while examining two additional constructs, namely, hope and optimism. 113 students (25 men, 88 women) between the ages of 17 to 24 years (M = 19.4, SD = 1.5) volunteered to participate. Positive correlations between executive function and gratitude were found but mixed results were obtained for forgiveness and satisfaction with life. Hope and optimism correlated positively with executive function and hierarchical multiple regression analysis indicated that they contributed significantly to the explanation of executive functioning. Further investigation into relationships between executive functioning, its neurobiological substrates, and positive psychological attributes is recommended.     

Executive functioning in older adults with mild cognitive impairment: MCI has effects on planning, but not on inhibition

In this study, we compared executive functioning in 32 mild cognitive impairment (MCI) individuals with that of normally aging controls. Cognitive planning tests (Trail Making, Porteus Maze Test, verbal fluency tests) show a group difference favoring the normal controls, but tests for inhibition of prepotent responses (no-go accuracy, two measures of the Stroop effect, and negative priming) failed to uncover a significant group difference. The results indicate that there is no general executive control function impairment in MCI; rather, the deficits found are compatible with the hypothesis that MCI is an accelerated form of normal aging.     

Executive control in a modified antisaccade task: Effects of aging and bilingualism

Two studies are reported that assess differences associated with aging and bilingualism in an executive control task. Previous work has suggested that bilinguals have an advantage over monolinguals in nonlinguistic tasks involving executive control; the major purpose of the present article is to ascertain which aspects of control are sensitive to the bilingual experience. Study 1 used an antisaccade task and found no effects of aging or bilingualism. Study 2 used the identical visual display but coupled to keypress responses. The results showed that bilinguals resolved various types of response conflict faster than monolinguals and that this bilingual advantage generally increased with age. A speculative interpretation of this pattern of results is offered in conclusion.     

Executive functioning and processing speed in age-related differences in memory: Contribution of a coding task

The aim of the present study was to examine executive dysfunctioning and decreased processing speed as potential mediators of age-related differences in episodic memory. We compared the performances of young and elderly adults in a free-recall task. Participants were also given tests to measure executive functions and perceptual processing speed and a coding task (the Digit Symbol Substitution Test, DSST). More precisely, we tested the hypothesis that executive functions would mediate the age-related differences observed in the free-recall task better than perceptual speed. We also tested the assumption that a coding task, assumed to involve both executive processes and perceptual speed, would be the best mediator of age-related differences in memory. Findings first confirmed that the DSST combines executive processes and perceptual speed. Secondly, they showed that executive functions are a significant mediator of age-related differences in memory, and that DSST performance is the best predictor.     

Aging of the planning process: the role of executive functioning

This study tested whether the aging of executive functioning is linked to the decline in planning performance. Participants were divided into three groups: group 1 composed of 15 adults with a mean age of 22.7 years, group 2 composed of 15 adults with a mean age of 68.1 years and group 3 composed of 16 adults with a mean age of 78.75 years. Each participant took tests for shifting, inhibition, updating and processing speed. Planning was evaluated by the Tower of Hanoi task with 3 and 4 disks. Analyses of variance showed a main age effect on the many executive functioning and planning measures assessed. Analyses of regression indicated that combined processing speed and shifting accounted for 58.33% of performance on the 3-disk version, while processing speed accounted for only 36.86% of performance on the 4-disk version. These results are discussed in relation to two levels of the planning process: formulation and execution.     

Executive functioning: Developmental consequences on adolescents with histories of maltreatment

Research suggests that children exposed to maltreatment have deficits in executive functioning (EF) but few studies have focused on the adolescent age group. We investigated whether maltreated adolescents had lower EF abilities compared to a group of non‐maltreated adolescents. Forty adolescents with histories of child maltreatment, together with a comparison group of 40 non‐maltreated adolescents matched for age, completed a comprehensive battery of EF tasks. Hierarchical multiple regression analyses, controlling for IQ, were carried out using each of the EF measures as dependent variables to examine group differences. Maltreated adolescents had significantly lower performance than non‐maltreated adolescents on tasks assessing executive loaded working memory, fluency, and inhibition, although switching was not impaired. Emotional and behavioural difficulties (EBD) were included in additional regression analyses to examine whether these variables would explain the group differences. The inclusion of EBD variables had some effect on group differences, as expected, but did not eliminate them. These findings support the theory that impairments in EF may be one underlying reason why adolescents with histories of maltreatment struggle to cope both inside and outside the classroom.     

Executive functioning in adolescent anorexia nervosa: Neuropsychology versus self- and parental-report

There is limited research concerning the relationship between neuropsychological assessment and self-report of executive functioning in adolescent anorexia nervosa (AN); available studies demonstrate only low to moderate correlations. Therefore, this study examines the association between neuropsychological test performance and self-report in AN. Forty adolescent inpatients with AN completed an extensive neuropsychological assessment, including set-shifting, central coherence, and questionnaires assessing executive functioning in daily life (BRIEF-SR). Their parents filled out an analog version (BRIEF-PF). Statistical analyses revealed low to medium positive and negative correlations between neuropsychological measures and BRIEF subscales. Similarly, self- and parental ratings were only slightly positively correlated, with patients scoring significantly higher than their parents on two subscales. The results support previous findings of modest correlations between self-report and performance-based testing and emphasize the importance of a multiple format assessment of executive functioning in adolescent AN.     

Executive functioning profiles in elite volleyball athletes: Preliminary results by a sport-specific task switching protocol

Executive functions (EF) are crucial for the athletes’ success, and they are even more essential in open skill sports (e.g. volleyball and football). In these sports, due to continuously changing conditions, goal-directed behaviours need to be repeatedly adjusted and corrected. One of the most important EF is the ability to continuously switch between two different tasks being required in a random sequence. We used a task-switching protocol in elite volleyball athletes, usually playing different roles, with the aim of evaluating if each role is characterized by specific switching abilities. On the basis of the specific competences requested by the game, thirty-six elite volleyball athletes were assigned to three groups: Strikers, Defenders and Mixed. Each player completed a customized sport-specific task-switching paradigm. Data evidenced that each role has specific characteristics. In Reaction Times, the Strikers were the fastest to answer to stimuli, while the Defender group provided a worse performance, particularly when defensive actions, that probably require more cognitive elaboration, had to be processed. Different effects emerged by the Errors. In fact, the Mixed group, which was the one with more expertise, appeared to be more accurate in the responses.Although preliminary, these results showed a minimal degree of cognitive flexibility for highly specialized Strikers and a maximum level for Mixed, allowing thus to highlight specific profiles of athletes. Data observed indicate the possibility to develop a test assessing the executive domain during the recruitment in a team, revealing a useful tool for choosing the most suitable role.     

The cerebellum in thought and action: a fronto-cerebellar aging hypothesis

Normal aging is associated with deficits in both memory and executive control. While a number of theories of cognitive aging have proposed that decrements in frontally mediated executive control processes can account for many of the age-related changes observed, the models proposed to date have not adequately accounted for age changes in processing speed, intra-individual variability and automaticity of information processing. These basic aspects of information processing efficiency may be of central importance for our understanding of age-related cognitive changes and more elaborate neurological models are needed that incorporate explanatory mechanisms which account for their influence. In this paper, it is proposed that the dual role played by frontal and cerebellar degeneration and the disruption of fronto-cerebellar feedback and feedforward control loops may be of central importance for a model of age-related changes in processing speed, intra-individual variability, automaticity, and higher level cognitive functions like memory and executive control.     

Executive functioning in individuals with a history of ASDs who have achieved optimal outcomes

Executive functioning (EF) is examined among children and adolescents once diagnosed with an autism spectrum disorder (ASD), but who no longer meet diagnostic criteria. These individuals have average social and language skills, receive minimal school support and are considered to have achieved “optimal outcomes” (OOs). Since residual impairments in these individuals might be expected in deficits central to autism, and in developmentally advanced skills, EF was examined in 34 individuals who achieved OOs, 43 individuals with high-functioning autism (HFA), and 34 typically developing (TD) peers. Groups were matched on age (M = 13.49), gender, and nonverbal IQ (NVIQ) but differed on verbal IQ (VIQ; HFA < TD, OO). On direct assessment, all three groups demonstrated average EF; however, the OO and HFA groups exhibited more impulsivity and less efficient planning and problem-solving than the TD group, and more HFA participants exhibited below average inhibition than did OO and TD participants. Parent-report measures revealed average EF among the OO and TD groups; however, the OO group exhibited more difficulty than the TD group on set-shifting and working memory. HFA participants demonstrated more difficulty on all parent-reported EF domains, with a clinical impairment in attention-shifting. Results suggest that EF in OO appears to be within the average range, even for functions that were impaired among individuals with HFA. Despite their average performance, however, the OO and TD groups differed on measures of impulsivity, set-shifting, problem-solving, working memory, and planning, suggesting that the OO group does not have the above-average EF scores of the TD group despite their high-average IQs.     

Prospective and retrospective memory in normal aging and dementia: an experimental study

Two experiments investigated the effects of normal aging and dementia on laboratory-based prospective memory (PM) tasks. Participants viewed a film for a later recognition memory task. In Experiment 1, they were also required either to say "animal" when an animal appeared in the film (event-based PM task) or to stop a clock every 3 min (time-based PM task). In both tasks, young participants were more successful than older participants, who were, in turn, more successful than patients with Alzheimer's disease (AD). For successful remembering in the time-based task, older participants and AD patients checked the clock more often than did young participants. In Experiment 2, participants were asked to reset a clock either when an animal appeared in the film (unrelated cue-action) or when a clock appeared in the film (related cue-action). Responses were faster in the related condition than in the unrelated condition. Again, there were differences in PM performance between young and older participants, and between older participants and AD patients. The observed deficits were not due to the forgetting of the PM task instructions in either experiment. Retrospective memory (RM) tasks (digit span, sentence span, free recall, and recognition) were more impaired by AD than were the PM tasks. Factor analysis revealed separate factors corresponding to RM and PM.     

Executive control of thought and action: in search of the wild homunculus

Executive control is studied in many areas of psychological research using a wide variety of procedures. This article focuses on studies of the executive processes involved in switching between tasks. The experiments discussed were designed to isolate and measure the duration of the executive processes required to switch from one task to another. However, the research is open to alternative interpretations that do not hypothesize executive processes, suggesting that task-switching procedures may not measure the duration of executive control. Further research is required to determine whether or not behavioral effects reflect the involvement of executive processes.     

Executive function in preschoolers: a review using an integrative framework

During the last 2 decades, major advances have been made in understanding the development of executive functions (EFs) in early childhood. This article reviews the EF literature during the preschool period using an integrative framework. The framework adopted considers EF to be a unitary construct with partially dissociable components (A. Miyake et al., 2000). The authors focus on 3 EF components: working memory, response inhibition, and shifting. For the present purposes, the central executive is conceived of as a central attention system that is involved in all EF component operations. Research to date suggests that elementary forms of the core EF components are present early during the preschool period. Changes in EF during the latter half of the preschool period appear to be due to the development of attention and integration of component EFs. Finally, the review outlines a number of areas that warrant further investigation if researchers are to move forward in understanding early EF development.     

Conceptual deficits and aging: the Category Test

Category Test performance of 41 bright aged normals was compared with the performance of 40 young normals and a group of 43 patients with suspected neurological dysfunction. The aged normals were not only as deficient as the neurologic patients but showed a similar pattern of deficits on Category subtests. The extreme difficulty experienced by aged normals and patients on Subtests III and IV was explained as a function of task complexity rather than of conceptual difficulty of conceptual principles and task complexity in a variety of impaired groups was suggested.