Exploring Age-Related Decline on the Wisconsin Card Sorting Test

The effect of age on task switching: updated and extended meta-analyses

Cognitive flexibility is one of the crucial abilities for human survival. As people get older, whether their flexibility ability will be affected is one of the core research topics in aging research. Researchers have developed a task-switch paradigm in laboratories to mimic daily-life shifting task-set scenarios. However, the empirical evidence is equivocal. Considering every single study may have a biased sample; therefore, we hoped to combine smaller studies, making them into one extensive investigation, which may help show an actual effect. In the current study, we used two meta-analysis techniques, the Brinley plot (along with the State-trace plot) and conventional meta-analysis, to re-evaluate whether healthy aging influences cognitive flexibility. The results of the Brinley plot analysis showed no evidence of switch-specific age-related impairment as indexed by the local switch cost. Yet, older adults performed more slowly than younger adults across task conditions. The conventional meta-analysis further showed that the currently available findings were heterogenous and exhibited publication bias. Therefore, this study suggests that researchers should interpret their results cautiously while using a task-switching paradigm to address older adults' shifting abilities. More parametric variables must be considered and developed in a task-switching paradigm to enhance its sensitivity and reveal older adults' actual shifting ability.

Neurocognitive and self-reported psychosocial and behavioral functioning in siblings of individuals with neurodevelopmental conditions: a study using remote self-administered testing

OBJECTIVE

This study compared and explored the neurocognitive profiles of siblings of persons with and without neurodevelopmental conditions (NDCs) and associations between objective test performance and self-reported psychosocial functioning.

METHODS

Siblings of persons with and without NDCs (64 NDC and 64 control siblings; mean age 19.88 years, range 11-27 years, 73.44% female, 75.78% White Caucasian) completed self-report questionnaires and self-administered computerized neurocognitive tests of executive functioning (EF). Using Bayesian analyses, we examined cross-sectional associations between self-reported psychosocial functioning and cognitive test performance, and predictors of EF over 15 months.

RESULTS

NDC siblings had poorer working memory, inhibition, attention, and shifting compared to controls, as measured by experimental paradigms on the backward Corsi span, N-Back 2-back task, Stop Signal Task, Sustained Attention to Response Task, and the Wisconsin Card Sorting Test (effect size δ ranging 0.49 to 0.64). Bayesian cross-sectional networks revealed negative emotion reactivity and working memory difficulties were central to the NDC sibling network. Over 15 months, poorer EF (k low test scores) was predicted by negative emotion reactivity, sleep problems, and anxiety, over and above effects of age and subclinical autistic and ADHD traits. Siblings of autistic individuals and persons with fetal alcohol spectrum disorder had higher rates of neurocognitive and psychiatric difficulties than other NDCs and controls (Bayes factors >20).

CONCLUSIONS

Neurocognitive difficulties were associated with transdiagnostic vulnerability to poorer wellbeing in NDC siblings. These findings demonstrate the feasibility of remote online cognitive testing and highlight the importance of individualized prevention and intervention for NDC siblings.

What determines cognitive estimation ability? Changing contributions of semantic and executive domains as a function of age

The Cognitive Estimation Test (CET) is commonly used in neuropsychological assessment. It is typically assumed to load on executive functions, although research has shown that CET performance also depends on access to semantic knowledge. It is unknown whether these contributions vary with age. It is important to examine this question as these abilities have divergent life course trajectories: executive functions tend to decline as people age but semantic knowledge continues to accrue. In addition, previous research has not examined potential contributions to CET performance from semantic control abilities, that is cognitive control processes involved specifically in the retrieval and use of semantic information. To address these questions, we investigated cognitive predictors of CET performance in healthy young and older adults. We found that better executive function was associated with more accurate estimation in both age groups. However, the effect of semantic knowledge on CET performance was significantly larger in older people, having no predictive power in the younger group. The ability to detect weak semantic associations, which is thought to index controlled search and retrieval of semantic information, also had divergent effects on CET performance in the two age groups. Our results provide empirical support for the idea that older people are more reliant on semantic knowledge when estimating quantities, which may explain why age‐related decline in CET scores is not typically found. We conclude that deficits on the CET may be indicative either of semantic or executive impairments, particularly in older age groups.

An Item Response Theory Analysis of the Wisconsin Card Sorting Test in Normal Aging, Alzheimer's Disease and Parkinson's Disease: Neurophysiological Approach

The Wisconsin Card Sorting Test (WCST) is widely used to assess executive function, specifically mental flexibility. Item Response Theory (IRT) has several advantages over classical test theory, including the invariance of the measure. This study aimed to apply IRT to study the psychometric properties of WCST in control subjects and patients with idiopathic Parkinson's disease (PD) and Alzheimer's disease (AD). The sample consisted of 86 controls, 77 Parkinson's disease subjects, and 155 AD subjects. The Rasch model was applied to binary data from the conversion to percentiles adjusted for age and schooling. The R program was used to calibrate the difficulty parameter. The characteristic curves of the items and the estimation of the difficulty parameter for each diagnostic group were obtained. WCST makes it possible to separate between different skill levels among the three diagnostic entities and its application may be useful for other neuropsychological tests. In conclusion, WCST has good clinical sensitivity and excellent discriminant validity in the groups under study, making it possible to separate them between different levels of ability or latent trait. Its application may be useful for other neuropsychological tests.

Low-Resolution Neurocognitive Aging and Cognition: An Embodied Perspective

Consistent with embodied cognition, a growing evidence in young adults show that sensorimotor processing is at the core of cognition. Considering that this approach predicts direct interaction between sensorimotor processing and cognition, embodied cognition may thus be particularly relevant to study aging, since this population is characterized by concomitant changes in sensorimotor and cognitive processing. The present perspective aims at showing the value and interest to explore normal aging throughout embodiment by focusing on the neurophysiological and cognitive changes occurring in aging. To this end, we report some of the neurophysiological substrates underpinning the perceptual and memory interactions in older adults, from the low and high perceptual processing to the conjunction in the medial temporal lobe. We then explore how these changes could explain more broadly the cognitive changes associated with aging in terms of losses and gains.

Attenuated NMDAR signaling on fast-spiking interneurons in prefrontal cortex contributes to age-related decline of cognitive flexibility

Ionotropic glutamate receptors of the NMDA and AMPA subtypes transduce excitatory signaling on neurons in the prefrontal cortex (PFC) in support of cognitive flexibility. Cognitive flexibility is reliably observed to decline at advanced ages, coinciding with changes in PFC glutamate receptor expression and neuronal physiology. However, the relationship between age-related impairment of cognitive flexibility and changes to excitatory signaling on distinct classes of PFC neurons is not known. In this study, one cohort of young adult (4 months) and aged (20 months) male F344 rats were characterized for cognitive flexibility on an operant set-shifting task. Expression of the essential NMDAR subunit, NR1, was correlated with individual differences in set-shifting abilities such that lower NR1 in the aged PFC was associated with worse set-shifting. In contrast, lower expression of two AMPAR subunits, GluR1 and GluR2, was not associated with set-shift abilities in aging. As NMDARs are expressed by both pyramidal cells and fast-spiking interneurons (FSI) in PFC, whole-cell patch clamp recordings were performed in a second cohort of age-matched rats to compare age-associated changes on these neuronal subtypes. Evoked excitatory postsynaptic currents were generated using a bipolar stimulator while AMPAR vs. NMDAR-mediated components were isolated using pharmacological tools. The results revealed a clear increase in AMPA/NMDA ratio in FSIs that was not present in pyramidal neurons. Together, these data indicate that loss of NMDARs on interneurons in PFC contributes to age-related impairment of cognitive flexibility.

Same room - different windows? A systematic review and meta-analysis of the relationship between self-report and neuropsychological tests of cognitive flexibility in healthy adults

Cognitive flexibility can be thought of as the ability to effectively adapt one's cognitive and behavioural strategies in response to changing task or environmental demands. To substantiate the common inference that self-report and neuropsychological tests of cognitive flexibility provide 'different windows into the same room', we undertook a systematic review and meta-analysis to determine whether self-report and neuropsychological tests of cognitive flexibility are related in healthy adults. Ten databases and relevant grey literature were searched from inception. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were adhered to. Twenty-one articles satisfied our inclusion criteria. A multi-level random-effects meta-analysis revealed no relationship (0.05, 95% CI = -0.00 to 0.10). Random-effects meta-analyses raised the possibility that the Cognitive Flexibility Scale and the Trail Making Test - part B (time) may be related (0.19, 95% CI = 0.06 to 0.31). We conclude that the relationship between self-report and neuropsychological tests of cognitive flexibility is not large enough to be considered convincing evidence for the two assessment approaches sharing construct validity. These results have clear implications for assessing and interpreting cognitive flexibility research and clinical practice.

Age Differences in the Subcomponents of Executive Functioning

OBJECTIVES

Across the life span, deficits in executive functioning (EF) are associated with poor behavioral control and failure to achieve goals. Though EF is often discussed as one broad construct, a prominent model of EF suggests that it is composed of three subdomains: inhibition, set shifting, and updating. These subdomains are seen in both younger (YA) and older adults (OA), with performance deficits across subdomains in OA. Therefore, our goal was to investigate whether subdomains of EF might be differentially affected by age, and how these differences may relate to broader global age differences in EF.

METHODS

To assess these age differences, we conducted a meta-analysis at multiple levels, including task level, subdomain level, and of global EF. Based on previous work, we hypothesized that there would be overall differences in EF in OA.

RESULTS

Using 1,268 effect sizes from 401 articles, we found overall differences in EF with age. Results suggested that differences in performance are not uniform, such that variability in age effects emerged at the task level, and updating was not as affected by age as other subdomains.

DISCUSSION

These findings advance our understanding of age differences in EF, and stand to inform early detection of EF decline.

Normative scores of the Wisconsin Card Sorting Test in a sample of the adult Portuguese population

OBJECTIVES

The Wisconsin Card Sorting Test (WCST) is a neuropsychological instrument that is widely used for assessment of executive functioning in both clinical and research settings. The aim of this study was to provide the normative scores for the WCST in a sample of Portuguese healthy adults.

METHODS

The data was collected from archival data in a total sample of 359 individuals, 149 men (41.5%, Mage = 38.3; SD = 20.3) and 210 women (58.5%, Mage = 52.2; SD = 19.4). Descriptive statistics were calculated to describe mean scores, standard-deviation and percentiles of the WCST indexes by gender, age and education. ANOVAs were used to explore the differences between these scores in sociodemographic variables. The normative scores were adjusted for age and educational level.

RESULTS

Significant statistical differences in mean scores were found in several WCST indexes, such as, total errors, perseverations, perseverative errors and conceptual level responses regarding age and education. Percentiles for WCST indexes were stratified by age group and educational level.

CONCLUSIONS

Age and education are important factors explaining performance on the WCST. This is the first study focused on the development of WCST normative scores for the adult Portuguese population, which can be applied in clinical, educational and research contexts.

Rhythm-Motor Dual Task Intervention for Fall Prevention in Healthy Older Adults

This study aimed to investigate the effects of a rhythm-motor dual task intervention on cognitive and gait control for older adults in relation to fall prevention. Ten healthy older adults participated in a rhythm-motor dual task intervention and 10 participated in the control group. The intervention group received 16 30-min intervention sessions for 8 weeks. During the intervention sessions, participants engaged in walking or bimanual tapping as a primary motor task with concurrent rhythm tasks including playing instruments and rhythmic chanting or singing. At pretest and post-test, measures of cognition, balance/mobility, and gait were administered. A significant difference between groups was found for part B of the Trail Making Test (TMT-B) measure that involved executive control of attention. Also, changes in the gait ratio in the dual task condition of walking while playing an instrument were significantly different between groups. The findings in this study support the use of the rhythm-motor dual task intervention for increasing available cognitive resources and improving gait control, which are critical factors in fall prevention.

Loss of NRF2 leads to impaired mitochondrial function, decreased synaptic density and exacerbated age-related cognitive deficits

Activation of the antioxidant regulatory transcription factor NRF2 (Nuclear factor erythroid-derived 2) regulates cellular bioenergetics and improves neuronal health in aging. Yet how NRF2 participates in maintaining synaptic, mitochondrial and cognitive function has not been fully elucidated. This study investigates how loss of NRF2 affects neuronal metabolism, synaptic density and cognitive performance in aged mice. Dendritic arborization as well as synaptic and mitochondrial gene expression was evaluated in hippocampal neurons isolated from mice lacking NRF2 (NRF2KO) and from wild-type (WT) C57BL6 mice. Mitochondrial function of these neurons was evaluated using the Seahorse XF platform. Additionally learning, memory and executive function were assessed in 20 month old NRF2KO and age-matched WT mice using conditioned fear response (CFR) and odor discrimination reversal learning (ODRL) tests. Hippocampal bioenergetics was profiled using mitochondria isolated from these animals and tissue was harvested for assessment of mitochondrial and synaptic genes. NRF2KO neurons had reduced dendritic complexity and diminished synaptic gene expression. This was accompanied by impaired mitochondrial function and decreased mitochondrial gene expression. Similar mitochondrial deficits were observed in the brains of aged NRF2KO mice. These animals also had significantly impaired cognitive performance and reduced synaptic gene expression as well. These data point to a role for NRF2 in maintaining mitochondrial and cognitive function during aging and suggest that the transcription factor may be a viable target for cognitive enhancing interventions. Because mitochondrial dysfunction and cognitive impairment also occur together in many neurodegenerative conditions there may be broad therapeutic potential of NRF2 activating agents.

Probabilistic Information Modulates the Timed Response Inhibition Deficit in Aging Mice

How interval timing is affected by aging constitutes one of the contemporary research questions. There is however a limited number of studies that investigate this research question in animal models of aging. The current study investigated how temporal decision-making is affected by aging. Initially, we trained young (2–3 month-old) and old C57BL/6J male mice (18–19 month-old) independently with short (3 s) and long (9 s) intervals by signaling, in each trial, the hopper associated with the interval that is in effect in that trial. The probability of short and long trials was manipulated (0.25 or 0.75) for different animals in each age group. During testing, both hoppers were illuminated, and thus active trial type was not differentiated. We expected mice to spontaneously combine the independently acquired time interval-location-probability information to adaptively guide their timing behavior in test trials. This adaptive ability and the resultant timing behavior were analyzed and compared between the age groups. Both young and old mice indeed adjusted their timing behavior in an abrupt fashion based on the independently acquired temporal-spatial-probabilistic information. The core timing ability of old mice was also intact. However, old mice had difficulty in terminating an ongoing timed response when the probability for the short trial was higher and this difference disappeared in the group that was exposed to a lower probability of short trials. These results suggest an inhibition problem in old mice as reflected through the threshold modulation process in timed decisions, which is cognitively penetrable to the probabilistic information.

Mental Flexibility Influences the Association Between Poor Balance and Falls in Older People - A Secondary Analysis

Impairments of balance predispose older people to falls. Some cognitive functions, especially executive functioning have been shown to affect balance and discriminate fallers from non-fallers. Mental flexibility is a component of the executive function and comprises multiple cognitive processes that work together to adjust the course of thoughts or actions according to the changing demands of a situation without the use of explicit instructions. However, the role of mental flexibility in balance in older people remains unclear. The study aim was to examine the relationship between mental flexibility and falls in a cohort of 212 older people (80.6 ± 4.9 years; 62% female). We hypothesized that: (i) participants with impaired balance would have worse mental flexibility compared to those with good balance; and (ii) poor mental flexibility would predict falls in the sub-group with impaired balance. Balance performance was assessed by measuring postural sway while standing on a medium density foam mat with eyes open for 30 s. Mental flexibility was assessed using a computerized short-form of the Wisconsin Card Sorting Test (WCST; 64 cards) with its sub-components comprising general performance, perseveration, failure-to-maintain set and conceptual ability. Falls were measured prospectively for 12-months using monthly calendars. MANCOVA revealed that WCST performance was associated with balance [Wilks' Lambda = 0.883, F = 2.168; p = 0.013, partial eta squared ( η p 2 ) = 0.061] due primarily to reduced concept formation ability [F _(2,207) = 5.787, p = 0.004, η p 2 = 0.053]. Negative binomial regression analysis adjusting for age, education, contrast sensitivity, proprioception, inhibition, and inhibitory choice stepping reaction time (iCSRT) revealed that lower concept formation ability was predictive for falls [Incidence Rate Ratio 1.048 (95% confidence interval 1.016-1.081)]. Further, lower concept formation ability partly explained the association between balance and falls: i.e., fallers in the upper balance tertile had reduced concept formation performance whereas non-fallers had similar concept formation performance across the three balance tertiles. These findings suggest that poor mental flexibility affects the ability to maintain steady balance contributing to increased risk of falls in older people.

Diagnostic precision of the Wisconsin Card Sorting Test in assessing cognitive deficits in substance use disorders

The Wisconsin Card Sorting Test (WCST) is a widely used neuropsychological instrument to assess executive functions related to cognitive flexibility and abstract reasoning. However, there is a lack of studies investigating the diagnostic precision of this instrument in substance use disorders. In this study, we aimed at assessing the sensitivity and specificity of the WCST in discriminating the performance of participants with substance use disorder with cognitive deficits and participants from the general population without cognitive deficits. The sample comprised three groups of participants with substance use disorders (opioid use disorder in harm reduction with methadone maintenance; opioid use disorder in treatment in a therapeutic community; alcohol use disorder in a therapeutic community) and a normative group of healthy adults. The total sample consisted of 587 participants that were assessed with cognitive tests for executive functions, general cognitive functioning, and self-reported depression. The results showed differences between groups in most WCST variables, providing evidence of discriminant validity for this test. Convergent validity was also established by weak to moderate correlations with general cognitive functioning. Cutoff points based on receiver operating characteristic (ROC) curves were calculated for the WCST variables. Overall, the WCST was sensitive to changes in cognitive flexibility and abstract reasoning that are key features of substance use disorders.

Association study of the functional Catechol-O-Methyltranferase (COMT) Val158Met polymorphism on executive cognitive function in a Thai sample

Catechol-O-Methyltranferase (COMT) plays a crucial role in the removal of cortical dopamine and is strongly implicated in human executive function. Numerous studies have reported associations of the COMT Val158Met (rs4680) polymorphism with executive function in healthy subjects. However, little work has investigated this in the Thai population and the relationship of age and education with this association remains unclear. Therefore, this study was designed to investigate the association of this polymorphism of the COMT gene with executive cognitive brain function in healthy subjects and the relationship with age and education. The Wisconsin Card Sorting Test (WCST) was performed to assess executive function in 254 healthy Thai subjects (aged 20-72 years). The results showed a significant association of rs4680 with executive function, in which Val/Met heterozygotes demonstrated better cognitive set shifting performance. Moreover, Met allele carriers showed a significantly stronger effect in the categories completed score than did Val homozygotes. Furthermore, age and education also showed a significant association with COMT genotype and WCST. These results revealed that executive cognitive function is associated with COMT genotype and influenced by age and/or education level in a Thai sample.

Centella asiatica attenuates hippocampal mitochondrial dysfunction and improves memory and executive function in β-amyloid overexpressing mice

Centella asiatica is a medicinal plant used to enhance memory. We have previously shown that a water extract of Centella asiatica (CAW) attenuates β-amyloid (Aβ)-induced spatial memory deficits in mice and improves neuronal health. Yet the effect of CAW on other cognitive domains remains unexplored as does its in vivo mechanism of improving Aβ-related cognitive impairment. This study investigates the effects of CAW on learning, memory and executive function as well as mitochondrial function and antioxidant response in the 5xFAD model of Aβ accumulation. Seven month old 5xFAD female mice were treated with CAW (2 mg/mL) in their drinking water for two weeks prior to behavioral testing. Learning, memory and executive function were assessed using the object location memory task (OLM), conditioned fear response (CFR) and odor discrimination reversal learning (ODRL) test. Mitochondrial function was profiled using the Seahorse XF platform in hippocampal mitochondria isolated from these animals and tissue was harvested for assessment of mitochondrial, antioxidant and synaptic proteins. CAW improved performance in all behavioral tests in the 5xFAD but had no effect on WT animals. Hippocampal mitochondrial function was improved and hippocampal and cortical expression of mitochondrial genes was increased in CAW-treated 5xFAD mice. Gene expression of the transcription factor NRF2, as well as its antioxidant target enzymes, was also increased with CAW treatment in both WT and 5xFAD mice. CAW treatment also decreased Aβ-plaque burden in the hippocampus of treated 5xFAD mice but had no effect on plaques in the cortex. These data show that CAW can improve many facets of Aβ-related cognitive impairment in 5xFAD mice. Oral treatment with CAW also attenuates hippocampal mitochondrial dysfunction in these animals. Because mitochondrial dysfunction and oxidative stress accompany cognitive impairment in many pathological conditions beyond Alzheimer's disease, this suggests potentially broad therapeutic utility of CAW.

Centella asiatica increases hippocampal synaptic density and improves memory and executive function in aged mice

INTRODUCTION

Centella asiatica is a plant used for centuries to enhance memory. We have previously shown that a water extract of Centella asiatica (CAW) attenuates age-related spatial memory deficits in mice and improves neuronal health. Yet the effect of CAW on other cognitive domains remains unexplored as does its mechanism of improving age-related cognitive impairment. This study investigates the effects of CAW on a variety of cognitive tasks as well as on synaptic density and mitochondrial and antioxidant pathways.

METHODS

Twenty-month-old CB6F1 mice were treated with CAW (2 mg/ml) in their drinking water for 2 weeks prior to behavioral testing. Learning, memory, and executive function were assessed using the novel object recognition task (NORT), object location memory task (OLM), and odor discrimination reversal learning (ODRL) test. Tissue was collected for Golgi analysis of spine density as well as assessment of mitochondrial, antioxidant, and synaptic proteins.

RESULTS

CAW improved performance in all behavioral tests suggesting effects on hippocampal and cortical dependent memory as well as on prefrontal cortex mediated executive function. There was also an increase in synaptic density in the treated animals, which was accompanied by increased expression of the antioxidant response gene NRF2 as well as the mitochondrial marker porin.

CONCLUSIONS

These data show that CAW can increase synaptic density as well as antioxidant and mitochondrial proteins and improve multiple facets of age-related cognitive impairment. Because mitochondrial dysfunction and oxidative stress also accompany cognitive impairment in many pathological conditions this suggests a broad therapeutic utility of CAW.

Decision Making under Ambiguity and Objective Risk in Higher Age - A Review on Cognitive and Emotional Contributions

The ability of decision making plays a highly relevant role in our survival, but is adversely affected during the process of aging. The present review aims to provide a better understanding of age-related differences in decision making and the role of cognitive and emotional factors in this context. We reviewed the literature about age-effects on decision-making performance, focusing on decision making under ambiguous and objective risk. In decisions under ambiguous risks, as measured by the Iowa Gambling Task, decisions are based on the experiences with consequences. In this case, many articles have attributed age-related impairments in decision making to changes in emotional and somatic reward- and punishment processing. In decisions under objective risks, as measured for example by the Game of Dice Task, decisions can be based on explicit information about risks and consequences. In this case, age-related changes have been attributed mainly to a cognitive decline, particularly impaired executive functions. However, recent findings challenge these conclusions. The present review summarizes neuropsychological and neurophysiological findings of age-related differences in decision making under ambiguous and objective risk. In this context, the relevance of learning, but also of cognitive and emotional contributors – responsible for age-related differences in decision making – are additionally pointed out.

Visual Acuity does not Moderate Effect Sizes of Higher-Level Cognitive Tasks

BACKGROUND/STUDY CONTEXT

Declining visual capacities in older adults have been posited as a driving force behind adult age differences in higher-order cognitive functions (e.g., the "common cause" hypothesis of Lindenberger & Baltes, 1994, Psychology and Aging, 9, 339-355). McGowan, Patterson, and Jordan (2013, Experimental Aging Research, 39, 70-79) also found that a surprisingly large number of published cognitive aging studies failed to include adequate measures of visual acuity. However, a recent meta-analysis of three studies (La Fleur and Salthouse, 2014, Psychonomic Bulletin & Review, 21, 1202-1208) failed to find evidence that visual acuity moderated or mediated age differences in higher-level cognitive processes. In order to provide a more extensive test of whether visual acuity moderates age differences in higher-level cognitive processes, we conducted a more extensive meta-analysis of topic.

METHODS

Using results from 456 studies, we calculated effect sizes for the main effect of age across four cognitive domains (attention, executive function, memory, and perception/language) separately for five levels of visual acuity criteria (no criteria, undisclosed criteria, self-reported acuity, 20/80-20/31, and 20/30 or better).

RESULTS

As expected, age had a significant effect on each cognitive domain. However, these age effects did not further differ as a function of visual acuity criteria.

CONCLUSION

The current meta-analytic, cross-sectional results suggest that visual acuity is not significantly related to age group differences in higher-level cognitive performance-thereby replicating La Fleur and Salthouse (2014). Further efforts are needed to determine whether other measures of visual functioning (e.g., contrast sensitivity, luminance) affect age differences in cognitive functioning.

Prefrontal cortical GABAergic signaling and impaired behavioral flexibility in aged F344 rats

The prefrontal cortex (PFC) is critical for the ability to flexibly adapt established patterns of behavior in response to a change in environmental contingencies. Impaired behavioral flexibility results in maladaptive strategies such as perseveration on response options that no longer produce a desired outcome. Pharmacological manipulations of prefrontal cortical GABAergic signaling modulate behavioral flexibility in animal models, and prefrontal cortical interneuron dysfunction is implicated in impaired behavioral flexibility that accompanies neuropsychiatric disease. As deficits in behavioral flexibility also emerge during the normal aging process, the goal of this study was to determine the role of GABAergic signaling, specifically via prefrontal cortical GABA(B) receptors, in such age-related deficits. Young and aged rats were trained in a set shifting task performed in operant chambers. First, rats learned to discriminate between two response levers to obtain a food reward on the basis of a cue light illuminated above the correct lever. Upon acquisition of this initial discrimination, the contingencies were shifted such that rats had to ignore the cue light and respond on the levers according to their left/right positions. Both young and aged rats acquired the initial discrimination similarly; however, aged rats were impaired relative to young following the set shift. Among aged rats, GABA(B) receptor expression in the medial prefrontal cortex (mPFC) was strongly correlated with set shifting, such that lower expression was associated with worse performance. Subsequent experiments showed that intra-mPFC administration of the GABA(B) receptor agonist baclofen enhanced set shifting performance in aged rats. These data directly link GABAergic signaling via GABA(B) receptors to impaired behavioral flexibility associated with normal aging.

Diagnostic Profiles of Patients Differentially Failing Executive Functioning Measures

OBJECTIVE

Limited research exists to explain differential executive functioning impairment in clinical populations, particularly between the Wisconsin Card Sorting Task (WCST) and the Trail Making Test (TMT).

METHODS

The distribution of clinical diagnoses was examined in patients failing none, one, or both tasks, and executive task performance was compared among dementia-related diagnoses. Two hundred and sixty-six participants received evaluations through an Alzheimer's Disease Research Center, which included executive tasks. Dementia-related diagnoses were established through consensus.

RESULTS

Chi-square analyses indicated that TMT failure, with or without WCST failure, possessed higher associations with dementia diagnoses. Repeated measures analysis of variance similarly indicated that participants with dementia, especially mild and moderate severity, performed worse on TMT.

CONCLUSIONS

Executive dysfunction was observed in dementia-related diagnoses, and TMT failure was implicated in dementia in higher proportions than WCST impairment. Trail Making Test appears more sensitive than WCST for assessing executive impairment across diagnoses, especially when time and resources are limited in screening and clinical settings.

Specifying Associations Between Conscientiousness and Executive Functioning: Mental Set Shifting, Not Prepotent Response Inhibition or Working Memory Updating

Conscientiousness is characterized by self-control, organization, and goal orientation and is positively related to a number of health and professional outcomes. Thus, it is commonly suggested that conscientiousness should be related to superior executive functioning (EF) abilities, especially prepotent response inhibition. However, little empirical support for this notion has emerged, perhaps due to oversimplified and underspecified modeling of EF. The current study sought to fill this gap by testing relations between conscientiousness and three facets of EF using a nested factors latent variable approach. Participants (N = 420; Mage  = 22.5; 50% male; 91% Caucasian) completed a measure of conscientiousness and nine EF tasks designed to tap three related yet distinguishable facets of EF: working memory updating, mental set shifting, and prepotent response inhibition. Structural equation models showed that conscientiousness is positively associated with the EF facet of mental set shifting but not response inhibition or working memory updating. Despite the common notion that conscientiousness is associated with cognitive abilities related to rigid control over impulses (i.e., inhibition), the current results suggest the cognitive ability most associated with conscientiousness is characterized by flexibility and the ability to adapt to changing environmental contingencies and task demands.

Language dominance and inhibition abilities in bilingual older adults

This study aimed to examine the so-called bilingual advantage in older adults' performance in three cognitive domains and to identify whether language use and bilingual type (dominant vs. balanced) predicted performance. The participants were 106 Spanish-English bilinguals ranging in age from 50 years to 84 years. Three cognitive domains were examined (each by a single test): inhibition (the Simon task), alternating attention (the Trail Making test), and working memory (Month Ordering). The data revealed that age was negatively correlated to performance in each domain. Bilingual type - balanced vs. dominant - predicted performance and interacted with age only on the inhibition measure (the Simon task). Balanced bilinguals showed age-related inhibition decline (i.e., greater Simon effect with increasing age); in contrast, dominant bilinguals showed little or no age-related change. The findings suggest that bilingualism may offer cognitive advantage in older age only for a subset of bilinguals.

Verbal and visuospatial executive functions in healthy elderly: The impact of education and frequency of reading and writing

Objective

To assess the predictive role of education and frequency of reading and writing habits (FRWH) on the cognitive flexibility, inhibition and planning abilities of healthy elderly individuals.

Methods

Fifty-seven healthy adults aged between 60 and 75 years with 2 to 23 years of formal education were assessed as to the frequency with which they read and wrote different types of text, as well as their number of years of formal education. Executive functions were evaluated using the Hayling Test and the Modified Wisconsin Card Sorting Test (MWCST).

Results

Weak to moderate positive correlations were found between education, FRWH and the number of categories completed in the MWCST, while negative correlations were identified between these variables and the number of perseverative and non-perseverative errors on the task. Only the FRWH was significantly correlated with the number of failures to maintain set. Speed and accuracy on the Hayling Test were only correlated with participant education. Both education and FRWH significantly predicted performance on the MWCST, and the combination of these two variables had a greater predictive impact on performance on this task than either of the two variables alone. Variability in scores on the Hayling Test was best accounted for by participant education.

Conclusion

In this sample of elderly subjects, cognitive flexibility was sufficiently preserved to allow for adequate performance on verbal tasks, but may have benefitted from the additional stimulation provided by regular reading and writing habits and by formal education in the performance of more complex non-verbal tasks.

Investigating the impact of nicotine on executive functions using a novel virtual reality assessment

AIMS

Nicotine is known to enhance aspects of cognitive functioning in abstinent smokers, but the effects on specific areas of executive functions and in non-smokers are inconclusive. This may be due in part to the poor sensitivity of tests used to assess executive functions. This study used a new virtual reality assessment of executive functions known as JEF (the Jansari assessment of Executive Functions) to address this issue.

DESIGN

A 2 × 2 design manipulating group (smokers and never-smokers) and drug [nicotine (4 mg for smokers; 2 mg for never smokers) versus placebo gum].

SETTING

School of Psychology; University of East London.

PARTICIPANTS

Seventy-two participants (aged 18-54 years): 36 minimally deprived (2 hours) smokers and 36 never-smokers.

MEASUREMENTS

Components of executive function were measured using the virtual reality paradigm JEF, which assesses eight cognitive constructs simultaneously as well as providing an overall performance measure.

FINDINGS

Univariate analyses of variance revealed that nicotine improved overall JEF performance, time-based prospective memory and event-based prospective memory in smokers (P < 0.01), but not in never-smokers. Action-based prospective memory was enhanced in both groups (P < 0.01) and never-smokers out-performed smokers on selective thinking and adaptive thinking (P < 0.01).

CONCLUSIONS

Executive functioning and prospective memory as aspects of cognitive performance can be enhanced by nicotine gum in smokers who have abstained for as little as 2 hours.

Distinct manifestations of executive dysfunction in aged rats

Different components of executive function such as working memory, attention, and cognitive flexibility can be dissociated behaviorally and mechanistically; however, the within-subject influences of normal aging on different aspects of executive function remain ill-defined. To better define these relationships, young adult and aged male F344 rats were cross-characterized on an attentional set-shifting task that assesses cognitive flexibility and a delayed response task that assesses working memory. Across tasks, aged rats were impaired relative to young; however, there was significant variability in individual performance within the aged cohort. Notably, performance on the set-shifting task and performance at long delays on the delayed response task were inversely related among aged rats. Additional experiments showed no relationship between aged rats' performance on the set-shifting task and performance on a hippocampal-dependent spatial reference memory task. These data indicate that normal aging can produce distinct manifestations of executive dysfunction, and support the need to better understand the unique mechanisms contributing to different forms of prefrontal cortical-supported executive decline across the lifespan.

Aging specifically impairs switching to an allocentric navigational strategy

Navigation abilities decline with age, partly due to deficits in numerous component processes. Impaired switching between these various processes (i.e., switching navigational strategies) is also likely to contribute to age-related navigational impairments. We tested young and old participants on a virtual plus maze task (VPM), expecting older participants to exhibit a specific strategy switching deficit, despite unimpaired learning of allocentric (place) and egocentric (response) strategies following reversals within each strategy. Our initial results suggested that older participants performed worse during place trial blocks but not response trial blocks, as well as in trial blocks following a strategy switch but not those following a reversal. However, we then separated trial blocks by both strategy and change type, revealing that these initial results were due to a more specific deficit in switching to the place strategy. Place reversals and switches to response, as well as response reversals, were unaffected. We argue that this specific "switch-to-place" deficit could account for apparent impairments in both navigational strategy switching and allocentric processing and contributes more generally to age-related decline in navigation.

The mouse attentional-set-shifting task: a method for assaying successful cognitive aging?

Humans exhibit considerable variance in cognitive decline with age, with some exhibiting little disruption and others becoming significantly impaired. In aged rodents, individual differences in spatial memory have been used to identify putative compensatory mechanisms underlying successful hippocampal aging. However, there are few parallel rodent models of cognitive decline in frontal-cortex-mediated functions. We tested the hypothesis that, like aged humans, aged mice would exhibit greater variance in executive function measures, as compared with young mice. We examined the performance of young and aged C57BL/6N mice in the attentional-set-shifting task. Whereas young and old mice did not differ on trials-to-criterion performance, aged mice exhibited significantly greater variance in mean correct latency-selective to the extradimensional shifting stage-as compared with their younger counterparts. Thus, this task may be used to identify mechanisms underlying individual differences in decline of frontal-mediated performances with age.

The relationship between working memory capacity and executive functioning: evidence for a common executive attention construct

Attentional control has been conceptualized as executive functioning by neuropsychologists and as working memory capacity by experimental psychologists. We examined the relationship between these constructs using a factor analytic approach in an adult life span sample. Several tests of working memory capacity and executive function were administered to more than 200 subjects between 18 and 90 years of age, along with tests of processing speed and episodic memory. The correlation between working memory capacity and executive functioning constructs was very strong (r = .97), but correlations between these constructs and processing speed were considerably weaker (rs approximately .79). Controlling for working memory capacity and executive function eliminated age effects on episodic memory, and working memory capacity and executive function accounted for variance in episodic memory beyond that accounted for by processing speed. We conclude that tests of working memory capacity and executive function share a common underlying executive attention component that is strongly predictive of higher level cognition.

When simple things are meaningful: working memory strength predicts children's cognitive flexibility

People often perseverate, repeating outdated behaviors despite correctly answering questions about rules they should be following. Children who perseverate are slower to respond to such questions than children who successfully switch to new rules, even after controlling for age and processing speed. Thus, switchers may have stronger working memory strength than perseverators, with stronger rule representations supporting both flexible switching and faster responses to questions. Alternatively, better inhibitory abilities may support switchers' faster responses by helping to resolve conflict. The current study tested these accounts using a new one-dimensional card sort. Even with all possible sources of conflict removed, switchers still responded faster than perseverators to questions about rules, supporting the graded working memory account.

Age differences in perseveration: cognitive and neuroanatomical mediators of performance on the Wisconsin Card Sorting Test

Aging effects on the Wisconsin Card Sorting Test (WCST) are fairly well established but the mechanisms of the decline are not clearly understood. In this study, we examined the cognitive and neural mechanisms mediating age-related increases in perseveration on the WCST. MRI-based volumetry and measures of selected executive functions in conjunction with the WCST were obtained in a sample of 117 healthy young and older adults. Path analysis indicated that age-related increase in perseveration is completely accounted for by declines in processing speed and temporal processing, deficits in working memory mediated by decreased prefrontal cortical volume, and the indirect influence of prefrontally-mediated declines in inhibition via working memory. We conclude that age-related increase in perseveration is indeed differentially dependent on the integrity of prefrontal cortex and on declines in selected cognitive processes dependent on this region.