John E. Fisk

Age-Related Impairment in Executive Functioning: Updating, Inhibition, Shifting, and Access

ABSTRACT Miyake, Friedman, Emerson, Witzki, Howerter and Wager (2000) have argued that the central executive is fractionated consisting of at least three separable component processes: updating, shifting, and inhibition. The Wisconsin Card Sort Test, random letter generation, Brooks spatial sequences, reading and computation span, word fluency, and a measure of dual task performance were administered to 95 individuals aged between 20 and 81, average age 41.89. The executive measures were factor analyzed, using the oblique rotation method, yielding four factors. The factor structure obtained was broadly consistent with Miyake et als. However, an additional factor, the only one not to show a significant performance decline with age, was also obtained and was believed to reflect the efficiency of access to long-term memory.

Working memory functioning in developmental dyslexia

Working memory impairments in dyslexia are well documented. However, research has mostly been limited to the phonological domain, a modality in which people with dyslexia have a range of problems. In this paper, 22 adult students with dyslexia and 22 age- and IQ-matched controls were presented with both verbal and visuospatial working memory tasks. Performance was compared on measures of simple span, complex span (requiring both storage and processing), and dynamic memory updating in the two domains. The dyslexic group had significantly lower spans than the controls on all the verbal tasks, both simple and complex, and also on the spatial complex span measure. Impairments remained on the complex span measures after controlling statistically for simple span performance, suggesting a central executive impairment in dyslexia. The novelty of task demands on the initial trials of the spatial updating task also proved more problematic for the dyslexic than control participants. The results are interpreted in terms of extant theories of dyslexia. The possibility of a supervisory attentional system deficit in dyslexia is also raised. It seems clear that working memory difficulties in dyslexia extend into adulthood, can affect performance in both the phonological and visuospatial modalities, and implicate central executive dysfunction, in addition to problems with storage.

Epilepsy, psychosocial and cognitive functioning

This article will provide an overview of the psychosocial and cognitive problems that people with epilepsy (PWE) experience as consequence of the condition and its treatment. Psychosocial problems will be discussed in light of how they impact on quality of life. The review will discuss the stigma, myths and stereotypes that PWE encounter and the implications of these for important psychological outcomes including; anxiety, depression, self-esteem, sense of mastery and cognitive dysfunction. The latter part of the article will focus on psychosocial factors including social isolation, interpersonal and family relationships and employment. The overall aim is to provide the reader with a general overview of the sort of factors that can impede social functioning in PWE with particular emphasis on the problems encountered in adults.

Investigating the central executive in adult dyslexics: Evidence from phonological and visuospatial working memory performance

There is long-standing evidence for verbal working memory impairments in both children and adults with dyslexia. By contrast, spatial memory appears largely to be unimpaired. In an attempt to distinguish between phonological and central executive accounts of the impairments in working memory, a set of phonological and spatial working memory tasks was designed to investigate the key issues in working memory, task type, task demands (static, dynamic, and updating), and task complexity. Significant differences emerged between the dyslexic and nondyslexic participants on the verbal working memory tasks employed in Experiment 1, thereby providing further evidence for continuing dyslexic impairments of working memory into adulthood. The nature of the deficits suggested a problem with the phonological loop, with there being little evidence to implicate an impairment of the central executive. Due to the difficulties associated with separating verbal working memory and phonological processing, however, performance was investigated in Experiment 2 using visuospatial measures of working memory. The results of the visuospatial tasks indicated no between-group differences in static spatial memory, which requires the short-term storage of simultaneously presented information. In almost all conditions there were no between-group differences in dynamic spatial memory that demands the recall of both location and order of stimuli presented sequentially. However, a significant impairment occurred on the dynamic task under high memory updating load, on which dyslexic adults showed nonphonological working memory deficits. In the absence of an explanation involving verbal recoding, this finding is interpreted in terms of a central executive or automaticity impairment in dyslexia.

The differential effects of ecstasy/polydrug use on executive components: shifting, inhibition, updating and access to semantic memory

Rationale/ObjectivesRecent theoretical models suggest that the central executive may not be a unified structure. The present study explored the nature of central executive deficits in ecstasy users.MethodsIn study 1, 27 ecstasy users and 34 non-users were assessed using tasks to tap memory updating (computation span; letter updating) and access to long-term memory (a semantic fluency test and the Chicago Word Fluency Test). In study 2, 51 ecstasy users and 42 non-users completed tasks that assess mental set switching (number/letter and plus/minus) and inhibition (random letter generation).ResultsMANOVA revealed that ecstasy users performed worse on both tasks used to assess memory updating and on tasks to assess access to long-term memory (C- and S-letter fluency). However, notwithstanding the significant ecstasy group-related effects, indices of cocaine and cannabis use were also significantly correlated with most of the executive measures. Unexpectedly, in study 2, ecstasy users performed significantly better on the inhibition task, producing more letters than non-users. No group differences were observed on the switching tasks. Correlations between indices of ecstasy use and number of letters produced were significant.ConclusionsThe present study provides further support for ecstasy/polydrug-related deficits in memory updating and in access to long-term memory. The surplus evident on the inhibition task should be treated with some caution, as this was limited to a single measure and has not been supported by our previous work.

Executive Working Memory Deficits in Abstinent Ecstasy/MDMA Users: A Critical Review

Aims: This review examined studies of executive functioning in abstinent ecstasy (3,4-methylenedioxymethamphetamine, MDMA) users on tasks which had been empirically mapped onto updating, shifting, inhibition and accessing long-term memory executive processes. Studies of some aspects of visuospatial memory performance were also included because of the investment of executive resources in such tasks. Methods:Thirty-three studies were identified for the review following searches of the Psychinfo and Medline databases. Inclusion criteria were the reporting of new empirical findings from participants drug free at the time of testing, in peer-reviewed journals in the English language. Results:Evidence for ecstasy-related performance deficits was strongest for the updating of verbal material, and for visuospatial memory tasks requiring additional processing beyond storage and retrieval. Such processing suggested that the overall level of executive demand was an important consideration. Executive shifting showed little evidence of ecstasy-related impairment, whilst examination of inhibition and long-term memory access presented an unclear picture. Conclusions: All but one of the studies had a cross-sectional design. Although this is a potential weakness with regard to confounds, the necessity of such designs was acknowledged. Studies were generally aware of the need to control for potential confounds, especially the effects of other drugs, through a mixture of group designs and statistical techniques. It was recommended that future studies of executive functioning in ecstasy users should detail the relationship of the tasks and dependent variables reported to specific executive processes and consider the level of executive demand imposed by such tasks.

Orienting Attention in Aging and Parkinson's Disease: Distinguishing Modes of Control

Past research on attentional orienting and Parkinsons disease (PD) has been compromised because the experimental paradigms tended to confound different forms of orienting. We sought to overcome this by examining the attentional orienting of three distinct groups (PD-patients, age-matched controls, and young controls) on five different tasks, four of which isolated pure forms of orienting. On two covert orienting tasks PD patients oriented volitional (Experiment 1) and reflexive (Experiment 2) covert attention in a healthy and normal manner for their age. On two overt orienting tasks, PD patients were found to execute volitional eye movements that were prone to undershoot their target goal (Experiment 3), and reflexive eye movements that were unusually fast (Experiment 4). When required to perform an antisaccade task (Experiment 5), which combines reflexive and volitional modes of overt orienting, PD patients performed normally This indicates that using a task which combines different modes of orienting creates a situation that is more than the sum of its parts. Together our study supports the thesis that it is crucial to isolate and investigate different modes of attentional control.

Assessing the functional significance of ecstasy-related memory deficits using a virtual paradigm.

Previous research shows that the use of ecstasy results in working memory and executive impairments in some users. The present study sought to assess the functional significance of such deficits using a virtual reality task.

The role of the executive system in visuo-spatial memory functioning

Participants were presented with a spatial sequence in which between 4 and 10 cells were highlighted. On each trial list length was unknown to the participant who was required to serially recall the last four cells. Processing of longer lists is assumed to call upon the executive system, which is thought to be involved in updating the contents of the short-term visuo-spatial store. Study 1 revealed that loading the executive system with concurrent random letter generation impaired performance on the spatial task especially recall of the early serial positions. However, contrary to expectation the degree of impairment was no greater on the longer lists, where it had been assumed that updating would be occurring. Study 2 confirmed this finding and demonstrated that relative to sequences of known length, under conditions of uncertainty when the list length was unknown, spatial recall was impaired even on short sequences. The present results support the growing consensus, which is suggestive of closer links between visuo-spatial and executive processes. However, it remains unclear whether or not updating is actually occurring on the longer sequences, and if it is, what specific executive processes are involved.

Evidence for executive deficits among users of MDMA (Ecstasy).

Random letter generation and computation span are tasks known to load on executive, prefrontal resources. Previous research suggests that Ecstasy users are impaired on random letter generation. The current study, employing a larger sample (44 current Ecstasy users, and 59 non-Ecstasy users), together with more effective statistical controls for other drug use, failed to replicate previous findings. Ecstasy users were unimpaired on all measures of random generation performance. A significant difference was obtained on the computation span measure, with Ecstasy users scoring significantly lower than non-Ecstasy users. This difference remained statistically significant following control for various indicators of the use of other drugs including cannabis. The results are discussed in terms of the potential effects that Ecstasy might have on different component executive processes.