Individual differences in executive functioning modulate age effects on the ERP correlates of retrieval success

The present study aimed to investigate whether the level of executive functioning modulated the effects of aging on episodic memory performance and on the electrophysiological correlates of retrieval success (‘old/new effect’). We used a differential approach in which young and older adults were divided into four groups of 14 participants according to their scores on a composite executive index: young-high, young-low, old-high and old-low. ERPs were recorded while participants performed a word-stem cued-recall task. Behavioral results demonstrated that age-related deficits in memory performance were reduced but not eliminated in individuals with a higher executive functioning level. Young participants exhibited ERP old/new effects on frontal and parietal areas. At posterior sites, the effect was entirely left-sided for young-low adults while for young-high participants it was bilateral, maximal at left sites and of greater amplitude. For the old-low group, both frontally-based and parietally-based processes appeared to be affected by the aging process. They also demonstrated a late frontal negative component, which might indicate an unsuccessful additional attempt to cope with retrieval difficulties. In the old-high group, ERP effects on frontal areas were relatively intact while the parietal effect was impaired compared to young adults. However, old-high subjects exhibited earlier, larger and more symmetrical effects than did old-low adults, which was in line with their better memory performance. These findings provide some support for the executive decline hypothesis of cognitive aging by showing that neural correlates of retrieval success in episodic memory are differentially affected by aging according to executive functioning level. They are consistent with the view that a high executive functioning level may help older adults recruit a cerebral pattern which enables them to perform a memory task more efficiently.     

Interplay between memory and executive functions in normal and pathological aging

Healthy older adults and Alzheimer's disease (AD) patients are reported in the literature to be impaired in memory and executive functions. This research investigates the extent of these two abilities in determining pathological aging. Groups of young-old and old-old healthy people (Experiment 1) and individuals with amnestic mild cognitive impairment (a-MCI) and AD (Experiment 2) were administered verbal and visuo-spatial tests graded for memory and/or executive requirements. Results indicate a decline in visuo-spatial tasks requiring memory and executive functions in healthy aging. The a-MCI showed memory deficits similar to those shown by AD, but preserved executive functions. Executive function decline could be the critical feature of dementia.     

Longitudinal change in neuropsychological performance using latent growth models: a study of mild cognitive impairment

The goal of the current study was to examine cognitive change in both healthy controls (n?=?229) and individuals with mild cognitive impairment (MCI) (n?=?397) from the Alzheimer’s Disease Neuroimaging Initiative (ADNI). We applied latent growth modeling to examine baseline and longitudinal change over 36 months in five cognitive factors derived from the ADNI neuropsychological test battery (memory, executive function/processing speed, language, attention and visuospatial). At baseline, MCI patients demonstrated lower performance on all of the five cognitive factors when compared to controls. Both controls and MCI patients declined on memory over 36 months; however, the MCI patients declined at a significantly faster rate than controls. The MCI patients also declined over 36 months on the remaining four cognitive factors. In contrast, the controls did not exhibit significant change over 36 months on the non-memory cognitive factors. Within the MCI group, executive function declined faster than memory, while the other factor scores changed slower than memory over time. These findings suggest different patterns of cognitive change in healthy older adults and MCI patients. The findings also suggest that, when compared with memory, executive function declines faster than other cognitive factors in patients with MCI. Thus, decline in non-memory domains may be an important feature for distinguishing healthy older adults and persons with MCI.     

The association between depressive mood and cognitive performance in an elderly general population - the MEMO Study

The aim of this study was to analyse the influence of the severity of depressive symptoms on different domains of cognitive function in the elderly. In a population-based cross-sectional study, 385 participants aged 65-83 years were interviewed with the Center for Epidemiologic Studies Depression Scale (CES-D) and performed a standardized neuropsychological test assessing attention, memory, cognitive speed and motor function. Multivariate linear regression analyses revealed a significant effect of depressive symptoms on a single test (Stroop test 1) and two summary scores (memory and motor function). After full adjustment for education and Mini Mental State Examination, the memory score was partly attenuated. Stratified analysis showed that an increase in CES-D scores led to a larger decline of cognitive test results in participants with mild to moderate depressive symptoms, compared to those with a high degree of depressive symptoms. Our results suggest that depressive mood in older adults is primarily associated with decreased processing speed and motor functioning, but not executive control functions. According to our results depressive mood is not necessarily associated with memory deficits in older adults. Changes in depressive symptoms in milder forms of depressive mood are associated with a larger decline in cognitive function than in severer forms of depressive mood.     

Aging with elevated autistic traits: Cognitive functioning among older adults with the broad autism phenotype

BackgroundLittle is known about the impact of aging with autism spectrum disorder (ASD) on cognition. As a first step in addressing this gap in our knowledge, the current study examined cognitive functioning among older adults with elevated, but subclinical levels of autistic traits (i.e., the Broad Autism Phenotype; BAP) compared to older adults without the BAP.MethodForty older adults (aged 60–91, M = 73 years) were recruited and classified as meeting criteria for the BAP (n = 20) or not (control older adults, COA; n = 20). Different components of executive function as well as episodic memory were measured using standardized performance-based neuropsychological assessments in addition to a self-report questionnaire of executive function difficulties.ResultsDespite no differences in age, sex ratio, educational history or IQ, the BAP group demonstrated poorer performance on measures of executive function and episodic memory compared to the COA group. The BAP group also self-reported more executive function difficulties in everyday settings. Moreover, differences in working memory and attentional shifting were maintained after accounting for the influences of IQ and both depression and anxiety symptoms.ConclusionsThese findings suggest that aging with the BAP confers additional risk to cognitive function for older adults. As the BAP forms a bridge in the continuum from typical to atypical levels of autistic traits, these findings suggest that individuals with ASD might also incur cognitive costs as they age into older adulthood.     

Understanding heterogeneity in older adults: Latent growth curve modeling of cognitive functioning

Background: Clarifying relationships between specific neurocognitive functions in cognitively intact older adults can improve our understanding of mechanisms involved in cognitive decline, which may allow identification of new opportunities for intervention and earlier detection of those at increased risk of dementia.

Method: The present study employed latent growth curve modeling to longitudinally examine the relationship between executive attention/processing speed, episodic memory, language, and working memory functioning utilizing the neuropsychological test battery from the National Alzheimer’s Disease Coordinating Center. A total of 691 relatively healthy older adults (M_age = 69.07, SD = 6.49) were assessed at baseline, and 553 individuals completed three visits spanning a two-year period.

Results: Better cognitive performance was concomitantly associated with better functioning across domains. Subtle declines in executive attention/processing speed processes were found, while, on average, memory and language performance improved with repeated testing. Lower executive attention/processing speed performance at baseline predicted less incremental growth rate in memory. In turn, higher initial memory functioning was associated with incremental improvements in language performance.

Conclusions: These results are consistent with the notion that intact executive function and attention processes are important to preserving memory functioning with advanced age, but are also the functions most susceptible to decline with age. These findings also provide further insight into the critical role of practice effects in clinical assessment practice and have implications for pharmaceutical trials. Practice effects should be routinely considered as they may give the appearance of retention of function within the cognitive domains considered to be a hallmark of Alzheimer’s disease pathology.     

Cognitive functioning over 3 years in community dwelling older adults with chronic partial epilepsy

Little is known about cognitive functioning of older adults with chronic partial epilepsy. We examined cognitive performance of this epilepsy patient group over 2-3 years. Seventeen older adults with epilepsy and 17 healthy older adults were administered measures of overall cognition and verbal memory at baseline and 2-3 years later. At baseline, older adults with epilepsy performed below controls on overall cognition and verbal memory (p's<0.001). These deficits generally remained stable at follow-up, although executive control appeared to decline (p<0.05). Older adults with epilepsy showed a failure to benefit from practice on a verbal memory measure (p=0.017). Older adults with epilepsy demonstrated cognitive deficits that generally are not progressive. A failure to benefit from repeat exposure to a Delayed Recall task could indicate learning deficits. These patients may also progressively lose executive control, possibly as a result of accelerated aging.     

Variable patterns of neuropsychological performance in HIV-1 infection

Based upon prior findings with group means, a "prototypical pattern" of neuropsychological results with HIV infection has emerged: impaired executive functioning, motor skills, speed of information processing, and learning, with intact memory retention, most language skills, and visuospatial functioning. We examined neuropsychological results from 553 HIV+ adults to determine the number of patterns seen among individuals with HIV infection. Factor analysis of a relatively comprehensive neuropsychological battery identified 6 component factors: verbal memory (VeM), visual memory (ViM), processing speed (PS), attention/working memory (A/WM), executive function (EF), and motor (M). These factor scores were submitted to hierarchical cluster analysis, to determine the appropriate number of clusters or patterns in the cohort. Final cluster membership was then determined by K-means analysis, based on the Lange, Iverson, Senior, and Chelune (2002) method. A 6-cluster solution was found to be most appropriate. The definitions of the clusters were based upon ipsative scoring of factor scores to indicate relative strengths and weaknesses (independent of overall level of performance): Cluster 1: strong EF; Cluster 2: strong M, weak VeM and EF; Cluster 3: strong PS, weak ViM and EF; Cluster 4: strong VeM, weak M; Cluster 5: strong A/WM; Cluster 6: strong VeM, weak EF. Neuropsychological-impairment rates differed across clusters, but all 6 clusters contained substantial numbers of impaired and unimpaired individuals. Cluster membership was not explained by demographic variables or psychiatric or neuromedical confounds. Thus, there does not appear to be a single, prototypical pattern of neuropsychological impairment associated with HIV infection for this battery of representative neuropsychological tests.     

Continuous positive airway pressure treatment for sleep apnea in older adults

Daytime sleepiness and sleep disordered breathing are increased in older compared to middle-aged adults. The cognitive and cardiovascular sequelae associated with obstructive sleep apnea (OSA) have significant implications for the older adult who may already be suffering from chronic illness. Most of the evidence supporting the utilization of continuous positive airway pressure (CPAP) for the treatment of OSA has been generated from studies employing samples consisting predominately of middle-aged adults. To examine the efficacy of CPAP for the treatment of obstructive sleep apnea in older adults with an emphasis on adherence and related treatment outcomes, this paper reviews findings from clinical trials including older individuals as well as those specifically targeting this population. These studies have demonstrated that following CPAP therapy, older adults have increased alertness, improved neurobehavioral outcomes in cognitive processing, memory, and executive function, decreased sleep disruption from nocturia and a positive effect on factors affecting cardiac function, including vascular resistance, platelet coagulability and other aspects of cardiovascular health. Physiological differences in respiratory structure and function between younger and older adults of similar disease severity are believed to result in older individuals requiring titration at lower CPAP levels. Once initiated, CPAP treatment is tolerated by older adults, including those with Alzheimer's disease. Patterns of adherence in older individuals are consistent with that of middle-aged adults.     

Cross-sectional and 35-year longitudinal assessment of salivary cortisol and cognitive functioning: the Vietnam Era twin study of aging

High levels of cortisol, a sign of potential hypothalamic-pituitary-adrenal (HPA) axis dysregulation, have been associated with poor cognitive outcomes in older adults. Most cortisol research has focused on hippocampal-related abilities such as episodic memory; however, the presence of glucocorticoid receptors in the human prefrontal cortex suggests that cortisol regulation is likely to be associated with prefrontally-mediated executive function abilities. We hypothesized that elevated cortisol levels would be associated with poorer frontal-executive function in addition to episodic memory. We assessed cortisol from 15 saliva samples paralleling individual diurnal rhythms across three non-consecutive days in a group of 778 middle-aged twin men ages 51-60. Cognitive domains created from 24 standard measures included: general cognitive ability, verbal and visual-spatial ability, verbal and visual-spatial memory, short-term/immediate memory, working memory, executive function, verbal fluency, abstract reasoning, and psychomotor processing speed. Adjusting for general cognitive ability at age 20, age, race, and multiple health and lifestyle indicators, higher levels of average area-under-the-curve cortisol output across three days were significantly associated with poorer performance in three domains: executive (primarily set-shifting) measures, processing speed, and visual-spatial memory. In a 35-year longitudinal component of the study, we also found that general cognitive ability at age 20 was a significant predictor of midlife cortisol levels. These results possibly support the notion that glucocorticoid exposure is associated with cognitive functions that are mediated by frontal-striatal systems, and is not specific to hippocampal-dependent memory. The results also suggest that the direction of effect is complex.     

Cognitive decline and hippocampal functional connectivity within older Black adults

While there has been a proliferation of neuroimaging studies on cognitive decline in older non‐Hispanic White adults, there is a dearth of knowledge regarding neuroimaging correlates of cognitive decline in Black adults. Resting‐state functional neuroimaging approaches may be particularly sensitive to early cognitive decline, but there are no studies that we know of that apply this approach to examining associations of brain function to cognition in older Black adults. We investigated the association of cognitive decline with whole‐brain voxel‐wise functional connectivity to the hippocampus, a key brain region functionally implicated in early Alzheimer''s dementia, in 132 older Black adults without dementia participating in the Minority Aging Research Study and Rush Memory and Aging Project, two longitudinal studies of aging that include harmonized annual cognitive assessments and magnetic resonance imaging brain imaging. In models adjusted for demographic factors (age, education, sex), global cognitive decline was associated with functional connectivity of the hippocampus to three clusters in the right and left frontal regions of the dorsolateral prefrontal cortex. In domain‐specific analyses, decline in semantic memory was associated with functional connectivity of the hippocampus to bilateral clusters in the precentral gyrus, and decline in perceptual speed was inversely associated with connectivity of the hippocampus to the bilateral intracalcarine cortex and the right fusiform gyrus. These findings elucidate neurobiological mechanisms underlying cognitive decline in older Black adults and may point to specific targets of intervention for Alzheimer''s disease.     

Cognitive features in euthymic bipolar patients in old age

Objectives:  Studies of cognition in bipolar disorder (BD) have reported impairments in processing speed, working memory, episodic memory, and executive function, but they have primarily focused on young and middle-aged adults. In such studies, the severity of cognitive deficits increases with the duration of illness. Therefore, one would expect more pronounced deficits in patients with longstanding BD. The first aim of the present study was to determine the pattern and the magnitude of cognitive impairment in older euthymic BD patients. The second aim was to explore the interrelationship between these cognitive deficits and determine whether they reflect a single core impairment or the co-occurrence of independent cognitive deficits.
Methods:  Twenty-two euthymic elderly BD patients and 22 controls, matched for gender, age, and education, underwent a comprehensive neuropsychological assessment.
Results:  Compared to controls, BD patients had significantly reduced performance in processing speed, working memory, verbal fluency, and episodic memory, but not in executive function. Hierarchical regression analyses showed that verbal fluency and working memory impairments were fully mediated by changes in processing speed. This was not the case for the episodic memory dysfunction.
Conclusion:  The cognitive profile in older euthymic BD cases is similar to the one described in younger BD cohorts. Our results further suggest that impaired processing speed plays a major role in the cognitive changes observed in BD patients except for deficits in episodic memory, thus providing strong evidence that processing speed and episodic memory are two core deficits in elderly BD patients.     

Cognitive function in older adults with major depression: Effects of mineralocorticoid receptor stimulation

Memory and executive function are often impaired in older adults with major depression. Mineralocorticoid receptors (MR) are abundantly expressed in the hippocampus and in the prefrontal cortex, brain areas critical for memory and executive function. In both aging and depression, MR expression in the brain is reduced. Therefore, diminished MR function could contribute to impaired cognition in older adults with depression and might be a promising target for pharmacological intervention.Twenty-three older adults with major depression (mean age 61.6 yrs ± 8.1, n = 13 women) without medication and 24 age-, sex- and education-matched healthy participants received the MR-agonist fludrocortisone (0.4 mg) or placebo in a randomized, double-blind, within-subject cross-over design. We measured psychomotor speed, executive function, verbal learning and memory, and visuospatial memory.Compared to controls, depressed patients performed worse in psychomotor speed (group effect p = 0.01), executive function (group effect p < 0.01), verbal learning (group effect p = 0.02), and verbal memory (group effect p < 0.01) but not in visuospatial memory. There were no significant treatment effects. However, we found a group × treatment interaction in verbal learning (p = 0.04) and visuospatial memory (p = 0.02) indicating that depressed patients performed worse after fludrocortisone whereas controls performed better after fludrocortisone.Our data suggest that –in contrast to younger depressed patients-older adults with depression do not benefit from MR stimulation but deteriorate in cognitive function.     

Age effects in time estimation: relationship to frontal brain morphometry

Compared with many other cognitive functions, relatively little is known about time representation in the brain. Recent work shows disrupted timing and time estimation in older adults, although it is unclear whether these effects are the result of normal aging or disease-related processes. The present study examined time estimation in persons across the adult lifespan who were free from significant medical or psychiatric history. Results showed older adults exhibited greater variability in time estimation, but no evidence for systematic acceleration or slowing emerged. This variability was correlated with performance on a variety of cognitive tests including attention, working memory and executive function. Although no relationship emerged between time estimation and EEG indices from central regions, multiple MRI indices were significantly correlated with time estimation. Stepwise regression showed volume of the supplementary motor area predicted variability in time estimation. These results indicate that healthy aging is associated with altered time estimation and suggest that changes in frontal brain regions mediate these effects.     

Preludes to brain failure: executive dysfunction and gait disturbances

The progressive and insidious gait and cognitive decline seen in older individuals without overt disease may result from a combination of age-dependent neuronal changes that are often exacerbated by vascular pathomechanisms. Emerging evidence suggests that slow gait and executive dysfunction are early phenomena in this decline and may further evolve to the development of falls and dementia. These early manifestations can be seen as “brain failure” and their co-occurrence suggests that they may share a common underlying mechanism. The authors argue that brain cortical control of motor and gait performance; and high complex cognitive functions such as executive function, share the same brain networks. Due to its particular watershed vascularization, these brain networks are highly susceptible to microvascular damage and the effects of vascular risk factors. A unified approach for evaluating and treating these two features of aging will close the gap in our understanding of cognitive–motor interactions and ultimately alter the pathways to disability. Besides the standard treatment for cognitive and mobility decline, the authors suggest that treating reversible vascular risk factors and hypertension, especially when they represent early manifestations of brain damage, has the potential to be a complementary method to prevent loss of mobility and cognitive decline in older adults.     

Associations Between the Prevalence,Treatment, Control of Hypertension and Cognitive Trajectories Among Chinese Middle-Aged and Older Adults

ObjectiveTo investigate the associations between the prevalence, treatment, control of hypertension, and trajectories of cognitive performance among Chinese middle-aged and older adults.DesignAn 8-year longitudinal study.SettingChina.ParticipantsChinese middle-aged and older adults.MeasurementsData from the China Health and Retirement Longitudinal Study were utilized. Group-based trajectory modeling was performed to identify heterogeneous trajectories of episodic memory and executive function. Multinomial logistic regression models were established to examine the relationships between hypertension status and cognitive trajectories, stratified by sex.ResultsThree episodic memory trajectories and four executive function trajectories were identified in males and females. Hypertension prevalence was associated with worse episodic memory and executive function trajectories in females. Compared with treated hypertensives, untreated hypertensives were more likely to have worse executive function trajectories, both in males and females. Among male treated hypertensives, those with uncontrolled blood pressure (BP) had worse episodic memory trajectories compared with their counterparts with controlled at standard targets, while females with uncontrolled BP demonstrated worse executive function trajectories compared with females controlled at standard targets. There was basically no significant difference in cognitive trajectory memberships between individuals with controlled hypertension corresponding to intensive or standard BP targets.ConclusionsThe prevalence of hypertension was associated with worse cognitive trajectories, and the treatment and control of hypertension were related to more favorable cognitive trajectories. Intensive BP control target was not associated with additional benefit beyond the recognized protective effect of standard BP targets on cognitive trajectories.     

Deep versus Periventricular White Matter Lesions and Cognitive Function in a Community Sample of Middle-Aged Participants

The association of cerebral white matter lesions (WMLs) with cognitive status is not well understood in middle-aged individuals. Our aim was to determine the specific contribution of periventricular hyperintensities (PVHs) and deep white matter hyperintensities (DWMHs) to cognitive function in a community sample of asymptomatic participants aged 50 to 65 years. One hundred stroke- and dementia-free adults completed a comprehensive neuropsychological battery and brain MRI protocol. Participants were classified according to PVH and DWMH scores (Fazekas scale). We dichotomized our sample into low grade WMLs (participants without or with mild lesions) and high grade WMLs (participants with moderate or severe lesions). Analyses were performed separately in PVH and DWMH groups. High grade DWMHs were associated with significantly lower scores in executive functioning (-0.45 standard deviations [SD]), attention (-0.42 SD), verbal fluency (-0.68 SD), visual memory (-0.52 SD), visuospatial skills (-0.79 SD), and psychomotor speed (-0.46 SD). Further analyses revealed that high grade DWMHs were also associated with a three- to fourfold increased risk of impaired scores (i.e.,<1.5 SD) in executive functioning, verbal fluency, visuospatial skills, and psychomotor speed. Our findings suggest that only DWMHs, not PVHs, are related to diminished cognitive function in middle-aged individuals. (JINS, 2012, 18, 1-12).     

Executive functions and selective attention are favored in middle-aged healthy women carriers of the Val/Val genotype of the catechol-o-methyltransferase gene: a behavioral genetic study

Background  

Cognitive deficits such as poor memory, the inability to concentrate, deficits in abstract reasoning, attention and set-shifting flexibility have been reported in middle-aged women. It has been suggested that cognitive decline may be due to several factors which include hormonal changes, individual differences, normal processes of aging and age-related changes in dopaminergic neurotransmission. Catechol-O-methyltransferase (COMT), a common functional polymorphism, has been related to executive performance in young healthy volunteers, old subjects and schizophrenia patients. The effect of this polymorphism on cognitive function in middle-aged healthy women is not well known. The aim of the current study was to investigate whether measures of executive function, sustained attention, selective attention and verbal fluency would be different depending on the COMT genotype and task demand.     

Cognitive profiles in heart failure: a cluster analytic approach

Cognitive impairment is common among individuals with heart failure (HF), but the exact nature of these impairments remains unclear. The current study examined 140 older adults with heart failure and sought to determine whether there are distinct cognitive profiles using a cluster analytic approach. Results indicated three unique profiles comprising individuals who were cognitively intact, memory impaired, and globally impaired. Clusters differed on several important demographic and clinical characteristics. These findings suggest that cognitive impairment in persons with HF is more heterogeneous than commonly believed and has important implications for treatment recommendations.