Memory aging and brain maintenance

Investigating the application of "Guttmann Cognitest"® in older adults and people with acquired brain injury

Introduction

Digital solutions for cognitive assessment are currently not only widely used in experimental contexts but can also be useful in clinical practice for efficient screening and longitudinal follow-up. The "Guttmann Cognitest"®, which includes seven computerized tasks designed to assess main cognitive functions, revealed in a previous validation study to be a potential useful tool to assess cognitive functioning in healthy middle-aged adults.

Method

Here, we present results from a validation in two different populations: one consisting of older adults, and the other comprising young and middle-aged individuals, some of them affected by acquired brain injury. To perform a convergent validity test, older adults were also administered with the MOCA, while young and middle-aged individuals were administered with a short neuropsychological assessment including gold-standard neuropsychological tests. We also conducted sensitivity and specificity analysis to establish the utility of this instrument in identifying potential cognitive dysfunctions in the two groups.

Results

Results demonstrated strong convergent validity as well as good specificity and sensitivity characteristics.

Discussion

This tool is a valid and useful instrument to assess cognitive functioning and detecting potential cases of cognitive dysfunctions in older adults and clinical populations.

Toward Personalized Cognitive Training in Older Adults: A Pilot Investigation of the Effects of Baseline Performance and Age on Cognitive Training Outcomes

BACKGROUND

Cognitive training holds potential as a non-pharmacological intervention to decrease cognitive symptoms associated with Alzheimer's disease (AD), but more research is needed to understand individual differences that may predict maximal training benefits.

OBJECTIVE

We conducted a pilot study using a six-month training regimen in healthy aging adults with no cognitive decline. We investigated the effects of baseline performance and age on training and transfer improvements.

METHODS

Out of 43 participants aged 65-84 years, 31 successfully completed cognitive training (BrainHQ) in one of three cognitive domains: processing speed (N = 13), inhibitory control (N = 9), or episodic memory (N = 9). We used standardized assessments to measure baseline performance and transfer effects.

RESULTS

All 31 participants improved on the cognitive training regimen and age was positively associated with training improvement (p = 0.039). The processing speed group improved significantly across many near- and far-transfer tasks. In the inhibitory control group, individuals with lower baseline performance improved more on inhibitory control and cognitive flexibility tasks. In the episodic memory group, older individuals improved most on a memory task while younger individuals improved most on an executive function far-transfer task.

CONCLUSIONS

Individual differences are predictive of cognitive training gains, and the impact of individual differences on training improvements is specific to the domain of training. We provide initial insight regarding how non-pharmacological interventions can be optimized to combat the onset of cognitive decline in older adults. With future research this work can inform the design of effective cognitive interventions for delaying cognitive decline in preclinical AD.

How long have you exercised in your life? The effect of motor reserve and current physical activity on cognitive performance

OBJECTIVES

Aging of the population encourages research on how to preserve cognition and quality of life. Many studies have shown that Physical Activity (PA) positively affects cognition in older adults. However, PA carried out throughout the individual's lifespan may also have an impact on cognition in old age. We hypothesize the existence of Motor Reserve (MR), a flexible and dynamic construct that increases over time and compensates for age-related motor and cognitive loss.

METHODS

Two questionnaires were developed and validated to estimate MR (Physical Activity carried out throughout the individual's lifespan) and Current Physical Activity (CPA, PA carried out in the previous 12 months). They were administered to 75 healthy individuals over 50 to verify the relation with cognition. MR and CPA include physical exercise (i.e., structured activities to improve or maintain physical fitness) and incidental PA, which we consider as any movement that leads to a metabolic cost above baseline (e.g., housekeeping, walking). In addition, the Cognitive Reserve Index questionnaire (CRI), a reliable predictor of cognitive performance, was used to measure each participant's Cognitive Reserve.

RESULTS

The factors that most influenced performance are Age and Cognitive Reserve, but also MR and CPA together and MR when it is the only factor.

CONCLUSIONS

Cognitive variability in adult and elderly populations is explained by both MR and CPA. PA training could profitably be included in new preventive and existing interventions.

Non-Surgical Site-Related Complications in Mandibular Fracture Surgery - A Problem of Elderly Patients?

BACKGROUND

Scientific evidence of nonsurgical site-related complications in mandibular fracture patients is limited.

PURPOSE

The purpose was to measure the frequency of nonsurgical site complications in patients with mandible fractures, describe the types of complications, and identify the risk factors associated with these complications.

STUDY DESIGN, SETTING, SAMPLE

A retrospective cohort study was conducted at the Helsinki University hospital between 2018 and 2021. Patients undergoing surgery with open reduction and internal fixation of mandibular fracture(s) were evaluated. Patients under 16 years of age were excluded.

PREDICTOR VARIABLE

Primary predictor variable was age. Patient-related predictor variables were sex, long-term disease(s), smoking, and alcohol and/or drug abuse. Injury and fracture-related variables were injury mechanism, type and site of facture, combined craniofacial fracture(s), and associated injury(s).

MAIN OUTCOME VARIABLE(S)

The primary outcome variable was nonsurgical site-related postoperative complication. The secondary outcome variable was type of complication.

COVARIATES

Not applicable.

ANALYSES

The main outcome variable was cross tabulated for pairwise comparisons with predictor variables. Multivariate logistic regression was performed for statistically significant (P < .05) variables.

RESULTS

The data included 314 patients (age range: 16 to 89 years; mean age: 38 years old; median age: 33 years old); most (78.3%) were men. Nonsurgical site-related postoperative complications occurred in 6.7% of patients. The most common complication type was pulmonary complication (36.0%), followed by urinary complication (20.0%) and general infection (16.0%). Nonsurgical site-related postoperative complications were most likely to occur in patients who were elderly (adjusted odds ratio [aOR] 5.55; 95% CI 1.92 to 16.21; P = .002), had combined craniofacial fractures (aOR 2.92; 95% CI 1.06 to 8.03; P = .038), and abused alcohol or drugs (aOR 4.51; 95% CI 1.70 to 11.96; P = .003). Pulmonary complications occurred more often in elderly patients, whereas urinary complications were more common in younger patients.

CONCLUSIONS AND RELEVANCE

The types of nonsurgical site complications in mandibular fracture patients increase and vary according to the patient's age. Awareness of possible complications related to different age groups helps anticipate and identify these in clinical work, and to consider the overall treatment of the patient beyond the fracture.

The Mediating Role of Cortical Atrophy on the Relationship between the Resilience Index and Cognitive Function: Findings from the Healthy Brain Initiative

Background

Lifestyle factors are linked to differences in brain aging and risk for Alzheimer's disease, underscored by concepts like 'cognitive reserve' and 'brain maintenance'. The Resilience Index (RI), a composite of 6 factors (cognitive reserve, physical and cognitive activities, social engagement, diet, and mindfulness) provides such a holistic measure.

Objective

This study aims to examine the association of RI scores with cognitive function and assess the mediating role of cortical atrophy.

Methods

Baseline data from 113 participants (aged 45+, 68% female) from the Healthy Brain Initiative were included. Life course resilience was estimated with the RI, cognitive performance with Cognivue®, and brain health using a machine learning derived Cortical Atrophy Score (CAS). Mediation analysis probed the relationship between RI, cognitive outcomes, and cortical atrophy.

Results

In age and sex adjusted models, the RI was significantly associated with CAS (β= -0.25, p = 0.006) and Cognivue® scores (β= 0.32, p < 0.001). The RI-Cognivue® association was partially mediated by CAS (β= 0.07; 95% CI [0.02, 0.14]).

Conclusions

Findings revealed that the collective effect of early and late-life lifestyle resilience factors on cognition are partially explained by their association with less brain atrophy. These findings underscore the value of comprehensive lifestyle assessments in understanding the risk and progression of cognitive decline and Alzheimer's disease in an aging population.

Adaptation behaviors modify the effects of body fat on heat-related symptoms among Taiwanese elderly

BACKGROUND

The aging process increases body fat and susceptibility to heat-related illnesses. The relationship between body composition and symptoms associated with exposure to extreme heat among the elderly is unclear. Additionally, the influence of individual adaptive behaviors in mitigating these risks has not been adequately explored.

OBJECTIVES

This study aimed to evaluate the association between body composition and heat-related symptoms as well as the potential modifying effects of heat adaptation behavior.

METHODS

The body composition of elderly individuals was measured using bioelectrical impedance analysis. Face-to-face interviews were conducted a year later to determine the heat-related symptoms and adaptive behaviors practiced for the extremely hot days of the previous year. The association between body composition indices and the presence of more than two symptoms was assessed using logistic regression analysis, while stratified analysis and interaction term in models were used to evaluate the effect modifications of adaptive behaviors.

RESULTS

Of the 859 participants, 16% reported more than two heat-related symptoms. Increased body fat mass index (fat mass in kg/squared height in meters) was associated with an elevated risk of more heat-related symptoms (odds ratio 1.11, 95% confidence interval 1.02-1.20). Each combination of staying indoors, using an umbrella and hat, and using air conditioning at noon reduced the risk association between body fat and symptoms. For females, a combination of reducing physical activity and staying indoors provided similar protective effect. Surprisingly, bathing more frequently in hot weather with heated instead of non-heated water augmented the risk correlation. Neither fan usage nor window opening displayed protective effects.

CONCLUSIONS

Elevated body fat levels, indicative of obesity, corresponded with an increased risk of heat-related symptoms. Integrating multiple adaptive behaviors can diminish the negative health impact of body fat on heat-induced symptoms. However, certain commonly adopted practices might not confer expected benefits.

Distinct age-related brain activity patterns in the prefrontal cortex when increasing cognitive load: A functional near-infrared spectroscopy study

Researchers have long observed distinct brain activity patterns in older adults compared with younger adults that correlate with cognitive performance. Mainly, older adults tend to show over-recruitment of bilateral brain regions during lower task loads and improved performance interpreted as compensation, but not observed at higher loads. However, there are discrepancies about whether increases in activity are compensatory and whether older adults can show compensation at higher loads. Our aim was to examine age-related differences in prefrontal cortex (PFC) activity and cognitive performance using functional near-infrared spectroscopy (fNIRS) during single and dual N-back tasks. Twenty-seven young adults (18-27 years) and 31 older adults (64-84 yrs) took part in the study. We used a robust fNIRS data methodology consisting of channel and region of interest analyses. Results showed differences in performance between task load conditions and age-related differences in reaction times but no age-group effects for accuracy. Older adults exhibited more bilateral PFC activation compared with young adults across all tasks and showed increases in brain activity in high compared to low load conditions. Our findings further support previous reports showing that older adults use compensatory recruitment of additional brain regions in PFC to maintain cognitive performance but go against the notion that such compensation is not present at higher cognitive loads. Additionally, our results indicate that fNIRS is a sensitive tool that can characterize adaptive cortical changes in healthy aging.

Grey-matter structure in cortical and limbic regions correlates with general cognitive ability in old age

According to the maintenance hypothesis (Nyberg et al., 2012), structural integrity of the brain's grey matter helps to preserve cognitive functioning into old age. A corollary of this hypothesis that can be tested in cross-sectional data is that grey-matter structural integrity and general cognitive ability are positively associated in old age. Building on Köhncke et al. (2021), who found that region-specific latent factors of grey-matter integrity are positively associated with episodic memory ability among older adults, we examine associations between general factors of grey-matter integrity and a general factor of cognitive ability in a cross-sectional sample of 1466 participants aged 60-88 years, 319 of whom contributed imaging data. Indicator variables based on T1-weighted images (voxel-based morphometry, VBM), magnetization-transfer imaging (MT), and diffusion tensor imaging-derived mean diffusivity (MD) had sufficient portions of variance in common to establish latent factors of grey-matter structure for a comprehensive set of regions of interest (ROI). Individual differences in grey-matter factors were positively correlated across neocortical and limbic areas, allowing for the definition of second-order, general factors for neocortical and limbic ROI, respectively. Both general grey-matter factors were positively correlated with general cognitive ability. For the basal ganglia, the three modality-specific indicators showed heterogenous loading patterns, and no reliable associations of the general grey-matter factor to general cognitive ability were found. To provide more direct tests of the maintenance hypothesis, we recommend applying the present structural modeling approach to longitudinal data, thereby enhancing the physiological validity of latent constructs of brain structure.

When Age Tips the Balance: a Dual Mechanism Affecting Hemispheric Specialization for Language

Aging engenders neuroadaptations, generally reducing specificity and selectivity in functional brain responses. Our investigation delves into the functional specialization of brain hemispheres within language-related networks across adulthood. In a cohort of 728 healthy adults spanning ages 18 to 88, we modeled the trajectories of inter-hemispheric asymmetry concerning the principal functional gradient across 37 homotopic regions of interest (hROIs) of an extensive language network, known as the Language-and-Memory Network. Our findings reveal that over two-thirds of Language-and-Memory Network hROIs undergo asymmetry changes with age, falling into two main clusters. The first cluster evolves from left-sided specialization to right-sided tendencies, while the second cluster transitions from right-sided asymmetry to left-hemisphere dominance. These reversed asymmetry shifts manifest around midlife, occurring after age 50, and are associated with poorer language production performance. Our results provide valuable insights into the influence of functional brain asymmetries on language proficiency and present a dynamic perspective on brain plasticity during the typical aging process.

Determinants of semantic and episodic memory decline among older adults in Ghana: Evidence from the WHO study on global AGEing and adult health Ghana wave 2

Objective

Determined factors associated with semantic (SM) and episodic memory (EM) among older adults aged 50 years and older in Ghana.

Methods

Data from WHO Study on Global AGEing and Adult Health (SAGE) Ghana Wave 2 was used for this study. Semantic memory (SM) and Episodic memory (EM) were the main study outcomes separately. The study employed Nested Ordinary Least Square regression analysis by sequentially adding 6 blocks of variables and comparison tests between the nested models.

Results

The study involved 3575 adult Ghanaians aged 50 years and older with a mean ± standard deviation of 62.6 ± 18.4 years. The overall mean ± SD of EM and SM were 5.86 ± 2.51 and 11.69 ± 8.59 respectively. Overall, analysis from block 6 showed a significant variation in SM by approximately 16.9%(ΔR2 = 1.17%) where increasing age, never married (β = -1.55; 95% CI = -2.41-0.69), being resident in Greater Accra (regional disparity) (β = -3.45; 95% CI = -4.73-2.20), underweight (β = -0.81;95% CI = -1.34-0.27), and moderate self-rated health (SRH) (β = -0.98; 95% CI = -1.52-0.45) significantly decreased SM. Similarly, increasing age, separated/divorced (β = -0.22; 95% CI = -0.35-0.87), being resident in Greater Accra (β = -0.53; 95% CI = -0.80-0.26), and moderate SRH (β = -0.20; 95% CI = -0.36--0.04) significantly decrease EM with an overall significant variation of approximately 22.9%(ΔR2 = 2.7%).

Conclusions

Increasing age, sex, marital status, regional disparity, and poor SRH significantly decreased both Semantic memory and Episodic memory. Higher educational attainment and life satisfaction significantly influenced SM and EM. These provide pointers to important socio-demographic determinants of SM and EM with implications for the implementation of the Ghana national ageing policy 2010, 'ageing with security and dignity', and as a key consideration for healthy ageing towards 2030.

The bidirectional effects between cognitive ability and brain morphology: A life course Mendelian randomization analysis

Introduction

Little is understood about the dynamic interplay between brain morphology and cognitive ability across the life course. Additionally, most existing research has focused on global morphology measures such as estimated total intracranial volume, mean thickness, and total surface area.

Methods

Mendelian randomization was used to estimate the bidirectional effects between cognitive ability, global and regional measures of cortical thickness and surface area, estimated total intracranial volume, total white matter, and the volume of subcortical structures (N=37,864). Analyses were stratified for developmental periods (childhood, early adulthood, mid-to-late adulthood; age range: 8-81 years).

Results

The earliest effects were observed in childhood and early adulthood in the frontoparietal lobes. A bidirectional relationship was identified between higher cognitive ability, larger estimated total intracranial volume (childhood, mid-to-late adulthood) and total surface area (all life stages). A thicker posterior cingulate cortex and a larger surface area in the caudal middle frontal cortex and temporal pole were associated with greater cognitive ability. Contrary, a thicker temporal pole was associated with lower cognitive ability.

Discussion

Stable effects of cognitive ability on brain morphology across the life course suggests that childhood is potentially an important window for intervention.

Implicit auditory memory in older listeners: From encoding to 6-month retention

Any listening task, from sound recognition to sound-based communication, rests on auditory memory which is known to decline in healthy ageing. However, how this decline maps onto multiple components and stages of auditory memory remains poorly characterised. In an online unsupervised longitudinal study, we tested ageing effects on implicit auditory memory for rapid tone patterns. The test required participants (younger, aged 20-30, and older adults aged 60-70) to quickly respond to rapid regularly repeating patterns emerging from random sequences. Patterns were novel in most trials (REGn), but unbeknownst to the participants, a few distinct patterns reoccurred identically throughout the sessions (REGr). After correcting for processing speed, the response times (RT) to REGn should reflect the information held in echoic and short-term memory before detecting the pattern; long-term memory formation and retention should be reflected by the RT advantage (RTA) to REGr vs REGn which is expected to grow with exposure. Older participants were slower than younger adults in detecting REGn and exhibited a smaller RTA to REGr. Computational simulations using a model of auditory sequence memory indicated that these effects reflect age-related limitations both in early and long-term memory stages. In contrast to ageing-related accelerated forgetting of verbal material, here older adults maintained stable memory traces for REGr patterns up to 6 months after the first exposure. The results demonstrate that ageing is associated with reduced short-term memory and long-term memory formation for tone patterns, but not with forgetting, even over surprisingly long timescales.

Extracellular matrix proteoglycans support aged hippocampus networks: a potential cellular-level mechanism of brain reserve

One hallmark of normative brain aging is vast heterogeneity in whether older people succumb to or resist cognitive decline. Resilience describes a brain's capacity to maintain cognition in the face of aging and disease. One factor influencing resilience is brain reserve-the status of neurobiological resources available to support neuronal circuits as dysfunction accumulates. This study uses a cohort of behaviorally characterized adult, middle-aged, and aged rats to test whether neurobiological factors that protect inhibitory neurotransmission and synapse function represent key components of brain reserve. Histochemical analysis of extracellular matrix proteoglycans, which play critical roles in stabilizing synapses and modulating inhibitory neuron excitability, was conducted alongside analyses of lipofuscin-associated autofluorescence. The findings indicate that aging results in lower proteoglycan density and more lipofuscin in CA3. Aged rats with higher proteoglycan density exhibited better performance on the Morris watermaze, whereas lipofuscin abundance was not related to spatial memory. These data suggest that the local environment around neurons may protect against synapse dysfunction or hyperexcitability and could contribute to brain reserve mechanisms.

Driving Difficulties and Preferences of Advanced Driver Assistance Systems by Older Drivers With Central Vision Loss

Purpose

The purpose of this study was to investigate driving difficulties and Advanced Driver Assistance Systems (ADAS) use and preferences of drivers with and without central vision loss (CVL).

Methods

Fifty-eight drivers with CVL (71 ± 13 years) and 68 without (72 ± 8 years) completed a telephone questionnaire. They rated their perceived driving difficulty and usefulness of technology support in 15 driving situations under good (daytime) and reduced visibility conditions, and reported their use experience and preferences for 12 available ADAS technologies.

Results

Drivers with CVL reported more difficulty (P = 0.002) and greater usefulness of technology support (P = 0.003) than non-CVL drivers, especially in reduced visibility conditions. Increased driving difficulty was associated with higher perceived technology usefulness (r = 0.34, P < 0.001). Dealing with blind spot road users, glare, unexpected pedestrians, and unfamiliar areas were perceived as the most difficult tasks that would benefit from technology support. Drivers with CVL used more advanced ADAS features than non-CVL drivers (P = 0.02), preferred to own the blind spot warning, pedestrian warning, and forward collision avoidance systems, and favored ADAS support that provided both information and active intervention. The perceived benefits of and willingness to own ADAS technologies were high for both groups.

Conclusions

Drivers with CVL used more advanced ADAS and perceived greater usefulness of driver assistance technology in supporting difficult driving situations, with a strong preference for collision prevention support.

Translational Relevance

This study highlights the specific technology needs and preferences of older drivers with CVL, which can inform future ADAS development, evaluation, and training tailored to this group.

Timing of lifespan influences on brain and cognition

Modifiable risk and protective factors for boosting brain and cognitive development and preventing neurodegeneration and cognitive decline are embraced in neuroimaging studies. We call for sobriety regarding the timing and quantity of such influences on brain and cognition. Individual differences in the level of brain and cognition, many of which present already at birth and early in development, appear stable, larger, and more pervasive than differences in change across the lifespan. Incorporating early-life factors, including genetics, and investigating both level and change will reduce the risk of ascribing undue importance and causality to proximate factors in adulthood and older age. This has implications for both mechanistic understanding and prevention.

Declining locus coeruleus-dopaminergic and noradrenergic modulation of long-term memory in aging and Alzheimer's disease

Memory is essential in defining our identity by guiding behavior based on past experiences. However, aging leads to declining memory, disrupting older adult's lives. Memories are encoded through experience-dependent modifications of synaptic strength, which are regulated by the catecholamines dopamine and noradrenaline. While cognitive aging research demonstrates how dopaminergic neuromodulation from the substantia nigra-ventral tegmental area regulates hippocampal synaptic plasticity and memory, recent findings indicate that the noradrenergic locus coeruleus sends denser inputs to the hippocampus. The locus coeruleus produces dopamine as biosynthetic precursor of noradrenaline, and releases both to modulate hippocampal plasticity and memory. Crucially, the locus coeruleus is also the first site to accumulate Alzheimer's-related abnormal tau and severely degenerates with disease development. New in-vivo assessments of locus coeruleus integrity reveal associations with Alzheimer's markers and late-life memory impairments, which likely stem from impaired dopaminergic and noradrenergic neurotransmission. Bridging research across species, the reviewed findings suggest that degeneration of the locus coeruleus results in deficient dopaminergic and noradrenergic modulation of hippocampal plasticity and thus memory decline.

Maintaining brain health across the lifespan

Across the lifespan, the human body and brain endure the impact of a plethora of exogenous and endogenous factors that determine the health outcome in old age. The overwhelming inter-individual variance spans between progressive frailty with loss of autonomy to largely preserved physical, cognitive, and social functions. Understanding the mechanisms underlying the diverse aging trajectories can inform future strategies to maintain a healthy body and brain. Here we provide a comprehensive overview of the current literature on lifetime factors governing brain health. We present the growing body of evidence that unhealthy alimentary regime, sedentary behaviour, sleep pathologies, cardio-vascular risk factors, and chronic inflammation exert their harmful effects in a cumulative and gradual manner, and that timely and efficient intervention could promote healthy and successful aging. We discuss the main effects and interactions between these risk factors and the resulting brain health outcomes to follow with a description of current strategies aiming to eliminate, treat, or counteract the risk factors. We conclude that the detailed insights about modifiable risk factors could inform personalized multi-domain strategies for brain health maintenance on the background of increased longevity.

Individual differences in age-related neurocognitive outcomes: within-subject assessment of memory for odors

Cognitive decline is a common feature of aging, particularly in memory domains supported by the medial temporal lobe (MTL). The ability to identify intervention strategies to treat or prevent this decline is challenging due to substantial variability between adults in terms of age of onset, rate and severity of decline, and many factors that could influence cognitive reserve. These factors can be somewhat mitigated by use of within-subject designs. Aged outbred Long-Evans rats have proven useful for identifying translationally relevant substrates contributing to age-related decline in MTL-dependent memory. In this population, some animals show reliable impairment on MTL-dependent tasks while others perform within the range of young adult rats. However, currently there are relatively few within-subject behavior protocols for assessing MTL function over time, and most require extensive training and appetitive motivation for associative learning. In the current study, we aimed to test whether water maze learning impairments in aged Long-Evans rats would be predictive of delayed recognition memory impairments and whether these odor memory impairments would be stable within subjects over multiple rounds of testing.

Age-Related Difference in Cognitive Performance under Severe Whole-Body Hyperthermia Parallels Cortisol and Physical Strain Responses

Background and Objectives: To date, understanding age-related changes in cognitive processes during heat exposure still needs to be better-understood. Thus, the main aim of the current study was to evaluate the effects of whole-body hyperthermia (WBH), i.e., a ≈ 2.5 °C increase in rectal temperature (Tre) from overnight-fast baseline value, on cognitive functioning in old and young men and to explore factors, such as stress and thermophysiological strain, that could influence such changes. Materials and Methods: Ten young (19-21 years of age) and nine old (61-80 years of age) healthy men underwent an experimental trial with passive lower-body heating in hot water immersion (HWI) at 43 °C (HWI-43 °C) until Tre reached 39 °C in old adults and 39.5 °C in young adults. Cognitive performance and cortisol concentration were assessed before and after HWI, and the physiological strain index (PSI) was assessed during HWI-43 °C. Results: PSI was lower and cortisol concentration was greater after HWI-43 °C in the old group compared with the young group (p < 0.05). Surprisingly, hyperthermia improved cognitive flexibility only in old adults, whereas short-term and visual recognition memories were maintained in both age groups. Conclusions: A ≈ 2.5 °C increase in rectal temperature can improve executive function in old adults, and this increase parallels the increased cortisol concentration and the lower thermophysiological strain under severe WBH conditions.

Conceptualizing healthy cognitive aging: the role of time and variability

The interest in healthy cognitive aging (HCA) has increased substantially over the past decade. Researchers are interested in exploring how health can be promoted and cognitive decline mitigated when pathology is not present. Identifying the necessary strategies is crucial as the gradual accumulation of small declines can lead to negative effects on quality of life over time. However, the conceptualization of HCA is not agreed upon. In fact, authors often turn to the use of traditional pathology screeners in the context of HCA because of their clear threshold results and their wide use in the different fields. This leads to the assumption that individuals are either cognitively unhealthy and therefore may have some form of dementia or are dementia-free and cognitively healthy. We believe that this view is an overly simplistic approach to the understanding of the aging process. In this work, we explore how HCA has been defined and conceptualized within the different fields. We further discuss how time and variability are key concepts that are often missing when studying HCA and propose a definition that aims to unify the findings from the multidisciplinary research that studies HCA and simplify the translation of knowledge. Incorporating these two novel dimensions to the study of HCA has already been proposed methodologically but has yet been discussed at the conceptual level. We believe that the proposed new approach will allow the identification of individual factors that cause changes in cognitive health and will help build new cognitive health strategies and mitigate further declines.

Neuroticism and white matter hyperintensities

Neuroticism is a major risk factor for neurodegenerative disorders, such as Alzheimer's disease and related dementias. This study investigates whether neuroticism is associated with white matter hyperintensities and whether this measure of brain integrity is a mediator between neuroticism and cognitive function. Middle-aged and older adults from the UK Biobank (N = 40,602; aged 45-82 years, M = 63.97, SD = 7.66) provided information on demographic and health covariates, completed measures of neuroticism and cognition, and underwent magnetic resonance imaging from which the volume of white matter hyperintensities was derived. Regression analyses that included age and sex as covariates found that participants who scored higher on neuroticism had more white matter hyperintensities (β = 0.024, 95% CI 0.015 to 0.032; p < .001), an association that was consistent across peri-ventricular and deep brain regions. The association was reduced by about 40% when accounting for vascular risk factors (smoking, obesity, diabetes, high blood pressure, heart attack, angina, and stroke). The association was not moderated by age, sex, college education, deprivation index, or APOE e4 genotype, and remained unchanged in sensitivity analyses that excluded individuals with dementia or those younger than 65. The mediation analysis revealed that white matter hyperintensities partly mediated the association between neuroticism and cognitive function. These findings identify white matter integrity as a potential neurobiological pathway that accounts for a small proportion of the association between neuroticism and cognitive health.

The integrity of dopaminergic and noradrenergic brain regions is associated with different aspects of late-life memory performance

Changes in dopaminergic neuromodulation play a key role in adult memory decline. Recent research has also implicated noradrenaline in shaping late-life memory. However, it is unclear whether these two neuromodulators have distinct roles in age-related cognitive changes. Here, combining longitudinal MRI of the dopaminergic substantia nigra-ventral tegmental area (SN-VTA) and noradrenergic locus coeruleus (LC) in younger (n = 69) and older (n = 251) adults, we found that dopaminergic and noradrenergic integrity are differentially associated with memory performance. While LC integrity was related to better episodic memory across several tasks, SN-VTA integrity was linked to working memory. Longitudinally, we found that older age was associated with more negative change in SN-VTA and LC integrity. Notably, changes in LC integrity reliably predicted future episodic memory. These differential associations of dopaminergic and noradrenergic nuclei with late-life cognitive decline have potential clinical utility, given their degeneration in several age-associated diseases.

Vascular cognitive impairment - Past, present, and future challenges

Vascular cognitive impairment (VCI) is a lifelong process encompassing a broad spectrum of cognitive disorders, ranging from subtle or mild deficits to prodromal and fully developed dementia, originating from cerebrovascular lesions such as large and small vessel disease. Genetic predisposition and environmental exposure to risk factors such as unhealthy lifestyles, hypertension, cardiovascular disease, and metabolic disorders will synergistically interact, yielding biochemical and structural brain changes, ultimately culminating in VCI. However, little is known about the pathological processes underlying VCI and the temporal dynamics between risk factors and disease mechanisms (biochemical and structural brain changes). This narrative review aims to provide an evidence-based summary of the link between individual vascular risk/disorders and cognitive dysfunction and the potential structural and biochemical pathophysiological processes. We also discuss some key challenges for future research on VCI. There is a need to shift from individual risk factors/disorders to comorbid vascular burden, identifying and integrating imaging and fluid biomarkers, implementing a life-course approach, considering possible neuroprotective influences of positive life exposures, and addressing biological sex at birth and gender differences. Finally, this review highlights the need for future researchers to leverage and integrate multidimensional data to advance our understanding of the mechanisms and pathophysiology of VCI.

Cognition's dependence on functional network integrity with age is conditional on structural network integrity

Maintaining good cognitive function is crucial for well-being across the lifespan. We proposed that the degree of cognitive maintenance is determined by the functional interactions within and between large-scale brain networks. Such connectivity can be represented by the white matter architecture of structural brain networks that shape intrinsic neuronal activity into integrated and distributed functional networks. We explored how the function-structure connectivity convergence, and the divergence of functional connectivity from structural connectivity, contribute to the maintenance of cognitive function across the adult lifespan. Multivariate analyses were used to investigate the relationship between function-structure connectivity convergence and divergence with multivariate cognitive profiles, respectively. Cognitive function was increasingly dependent on function-structure connectivity convergence as age increased. The dependency of cognitive function on connectivity was particularly strong for high-order cortical networks and subcortical networks. The results suggest that brain functional network integrity sustains cognitive functions in old age, as a function of the integrity of the brain's structural connectivity.

Effects of Brain Maintenance and Cognitive Reserve on Age-Related Decline in Three Cognitive Abilities

OBJECTIVES

Age-related cognitive changes can be influenced by both brain maintenance (BM), which refers to the relative absence over time of changes in neural resources or neuropathologic changes, and cognitive reserve (CR), which encompasses brain processes that allow for better-than-expected behavioral performance given the degree of life-course-related brain changes. This study evaluated the effects of age, BM, and CR on longitudinal changes over 2 visits, 5 years apart, in 3 cognitive abilities that capture most of age-related variability.

METHODS

Participants included 254 healthy adults aged 20-80 years at recruitment. Potential BM was estimated using whole-brain cortical thickness and white matter mean diffusivity at both visits. Education and intelligence quotient (IQ; estimated with American National Adult Reading Test) were tested as moderating factors for cognitive changes in the 3 cognitive abilities.

RESULTS

Consistent with BM-after accounting for age, sex, and baseline performance-individual differences in the preservation of mean diffusivity and cortical thickness were independently associated with relative preservation in the 3 abilities. Consistent with CR-after accounting for age, sex, baseline performance, and structural brain changes-higher IQ, but not education, was associated with reduced 5-year decline in reasoning (β = 0.387, p = .002), and education was associated with reduced decline in speed (β = 0.237, p = .039).

DISCUSSION

These results demonstrate that both CR and BM can moderate cognitive changes in healthy aging and that the 2 mechanisms can make differential contributions to preserved cognition.

The association between personality and plasma biomarkers of astrogliosis and neuronal injury

Personality traits have been associated with the risk of dementia and Alzheimer's disease neuropathology, including amyloid and tau. This study examines whether personality traits are concurrently related to plasma glial fibrillary acidic protein (GFAP), a marker of astrogliosis, and neurofilament light (NfL), a marker of neuronal injury. Cognitively unimpaired participants from the Baltimore Longitudinal Study on Aging (N = 786; age: 22-95) were assayed for plasma GFAP and NfL and completed the Revised NEO Personality Inventory, which measures 5 domains and 30 facets of personality. Neuroticism (particularly vulnerability to stress, anxiety, and depression) was associated with higher GFAP and NfL. Conscientiousness was associated with lower GFAP. Extraversion (particularly positive emotions, assertiveness, and activity) was related to lower GFAP and NfL. These associations were independent of demographic, behavioral, and health covariates and not moderated by age, sex, or apolipoprotein E genotype. The personality correlates of astrogliosis and neuronal injury tend to be similar, are found in individuals without cognitive impairment, and point to potential neurobiological underpinnings of the association between personality traits and neurodegenerative diseases.

Expressive recall and recognition as complementary measures to assess novel word learning ability in aphasia

Novel word learning ability has been associated with language treatment outcomes in people with aphasia (PWA), and its assessment could inform prognosis and rehabilitation. We used a brief experimental task to examine novel word learning in PWA, determine the value of phonological cueing in assessing learning outcomes, and identify factors that modulate learning ability. Twelve PWA and nineteen healthy controls completed the task, and recall and recognition tests of learning ability. Most PWA showed comparable learning outcomes to those of the healthy controls. Learning assessed via expressive recall was more clearly evidenced with phonological cues. Better single word processing abilities and phonological short-term memory and higher integrity of the left inferior frontal gyrus were related to better learning performance. Brief learning tasks like this one are clinically feasible and hold promise as screening tools of verbal learning in PWA once validated and evaluated for their capacity to predict treatment outcomes.

The effects of typical ageing on cognitive control: recent advances and future directions

Cognitive control is one of the most fundamental aspects of human life. Its ageing is an important contemporary research area due to the needs of the growing ageing population, such as prolonged independence and quality of life. Traditional ageing research argued for a global decline in cognitive control with age, typically characterised by slowing processing speed and driven by changes in the frontal cortex. However, recent advances questioned this perspective by demonstrating high heterogeneity in the ageing data, domain-specific declines, activity changes in resting state networks, and increased functional connectivity. Moreover, improvements in neuroimaging techniques have enabled researchers to develop compensatory models of neural reorganisation that helps negate the effects of neural losses and promote cognitive control. In this article on typical ageing, we review recent behavioural and neural findings related to the decline in cognitive control among older adults. We begin by reviewing traditional perspectives and continue with how recent work challenged those perspectives. In the discussion section, we propose key areas of focus for future research in the field.

The multifactorial nature of healthy brain ageing: Brain changes, functional decline and protective factors

As the global population faces a progressive shift towards a higher median age, understanding the mechanisms underlying healthy brain ageing has become of paramount importance for the preservation of cognitive abilities. The first part of the present review aims to provide a comprehensive look at the anatomical changes the healthy brain endures with advanced age, while also summarizing up to date findings on modifiable risk factors to support a healthy ageing process. Subsequently, we describe the typical cognitive profile displayed by healthy older adults, conceptualizing the well-established age-related decline as an impairment of four main cognitive factors and relating them to their neural substrate previously described; different cognitive trajectories displayed by typical Alzheimer's Disease patients and successful agers with a high cognitive reserve are discussed. Finally, potential effective interventions and protective strategies to promote cognitive reserve and defer cognitive decline are reviewed and proposed.

Tau and amyloid biomarkers modify the degree to which cognitive reserve and brain reserve predict cognitive decline

OBJECTIVE

Brain reserve, cognitive reserve, and education are thought to protect against late-life cognitive decline, but these variables have not been directly compared to one another in the same model, using future cognitive and functional decline as outcomes. We sought to determine whether the influence of these protective factors on executive function (EF) and daily function decline was dependent upon Alzheimer's disease (AD) pathology severity, as measured by the total tau to beta-amyloid (T-τ/Aβ1-42) ratio in cerebrospinal fluid (CSF).

METHOD

Participants were 1201 older adult volunteers in the Alzheimer's Disease Neuroimaging Initiative (ADNI) study. Brain reserve was defined using a composite index of structural brain volumes (total brain matter, hippocampus, and white matter hyperintensity). Cognitive reserve was defined as the variance in episodic memory performance not explained by brain integrity and demographics.

RESULTS

At higher levels of T-τ/Aβ1-42, brain and cognitive reserve predicted slower decline in EF. Only brain reserve attenuated decline at lower levels of T-τ/Aβ1-42. Education had no independent association with cognitive decline.

CONCLUSIONS

These results point to a hierarchy of protection against aging- and disease-associated cognitive decline. When pathology is low, only structural brain integrity predicts rate of future EF decline. The ability of cognitive reserve to predict future EF decline becomes stronger as CSF biomarker evidence of AD increases. Although education is typically thought of as a proxy for cognitive reserve, it did not show any protective effects on cognition after accounting for brain integrity and the residual cognitive reserve index.

No moderating influence of education on the association between changes in hippocampus volume and memory performance in aging

Contemporary accounts of factors that may modify the risk for age-related neurocognitive disorders highlight education and its contribution to a cognitive reserve. By this view, individuals with higher educational attainment should show weaker associations between changes in brain and cognition than individuals with lower educational attainment. We tested this prediction in longitudinal data on hippocampus volume and episodic memory from 708 middle-aged and older individuals using local structural equation modeling. This technique does not require categorization of years of education and does not constrain the shape of relationships, thereby maximizing the chances of revealing an effect of education on the hippocampus-memory association. The results showed that the data were plausible under the assumption that there was no influence of education on the association between change in episodic memory and change in hippocampus volume. Restricting the sample to individuals with elevated genetic risk for dementia (APOE ε4 carriers) did not change these results. We conclude that the influence of education on changes in episodic memory and hippocampus volume is inconsistent with predictions by the cognitive reserve theory.

Does physical fitness affect cognitive functions differently across adulthood? An advantage of being older

Introduction

There is a large interindividual variability in cognitive functioning with increasing age due to biological and lifestyle factors. One of the most important lifestyle factors is the level of physical fitness (PF). The link between PF and brain activity is widely accepted but the specificity of cognitive functions affected by physical fitness across the adult lifespan is less understood. The present study aims to clarify whether PF is basically related to cognition and general intelligence in healthy adults, and whether higher levels of PF are associated with better performance in the same or different cognitive functions at different ages.

Methods

A sample of 490 participants (20-70 years) was analyzed to examine this relationship. Later, the sample was split half into the young to middle-aged group (YM; 20-45 years; n = 254), and the middleaged to older group (MO; 46-70 years; n = 236). PF was measured by a quotient of maximum power in a bicycle ergometry test PWC-130 divided by body weight (W/kg), which was supported by a self-reported level of PF. Cognitive performance was evaluated by standardized neuropsychological test batteries.

Results

Regression models showed a relationship between PF and general intelligence (g-factor) and its subcomponents extracted using structural equation modeling (SEM) in the entire sample. This association was moderated by age, which also moderated some specific cognitive domains such as attention, logical reasoning, and interference processing. After splitting the sample into two age groups, a significant relationship was found between cognitive status, as assessed by the Mini Mental State Examination (MMSE), and PF in both age groups. However, apart from cognitive failures in daily life (CFQ), no other association between PF and specific cognitive functions was found in the YM group. In contrast, several positive associations were observed in the MO group, such as with selective attention, verbal memory, working memory, logical reasoning, and interference processing.

Discussion

These findings show that middle-aged to older adults benefit more from PF than younger to middle-aged adults. The results are discussed in terms of the neurobiological mechanisms underlying the cognitive effects of PF across the lifespan.

Clinical trial registration

https://clinicaltrials.gov/ct2/show/NCT05155397, identifier NCT05155397.

Dopamine D1-signaling modulates maintenance of functional network segregation in aging

Past research has shown that as individuals age, there are decreases in within-network connectivity and increases in between-network connectivity, a pattern known as functional dedifferentiation. While the mechanisms behind reduced network segregation are not fully understood, evidence suggests that age-related differences in the dopamine (DA) system may play a key role. The DA D1-receptor (D1DR) is the most abundant and age-sensitive receptor subtype in the dopaminergic system, known to modulate synaptic activity and enhance the specificity of the neuronal signals. In this study from the DyNAMiC project (N = 180, 20-79y), we set out to investigate the interplay among age, functional connectivity, and dopamine D1DR availability. Using a novel application of multivariate Partial Least squares (PLS), we found that older age, and lower D1DR availability, were simultaneously associated with a pattern of decreased within-network and increased between-network connectivity. Individuals who expressed greater distinctiveness of large-scale networks exhibited more efficient working memory. In line with the maintenance hypotheses, we found that older individuals with greater D1DR in caudate exhibited less dedifferentiation of the connectome, and greater working memory, compared to their age-matched counterparts with less D1DR. These findings suggest that dopaminergic neurotransmission plays an important role in functional dedifferentiation in aging with consequences for working memory function at older age.

The relationship between resting-state amplitude fluctuations and memory-related deactivations of the default mode network in young and older adults

The default mode network (DMN) typically exhibits deactivations during demanding tasks compared to periods of relative rest. In functional magnetic resonance imaging (fMRI) studies of episodic memory encoding, increased activity in DMN regions even predicts later forgetting in young healthy adults. This association is attenuated in older adults and, in some instances, increased DMN activity even predicts remembering rather than forgetting. It is yet unclear whether this phenomenon is due to a compensatory mechanism, such as self-referential or schema-dependent encoding, or whether it reflects overall reduced DMN activity modulation in older age. We approached this question by systematically comparing DMN activity during successful encoding and tonic, task-independent, DMN activity at rest in a sample of 106 young (18-35 years) and 111 older (60-80 years) healthy participants. Using voxel-wise multimodal analyses, we assessed the age-dependent relationship between DMN resting-state amplitude (mean percent amplitude of fluctuation, mPerAF) and DMN fMRI signals related to successful memory encoding, as well as their modulation by age-related hippocampal volume loss, while controlling for regional grey matter volume. Older adults showed lower resting-state DMN amplitudes and lower task-related deactivations. However, a negative relationship between resting-state mPerAF and subsequent memory effect within the precuneus was observed only in young, but not older adults. Hippocampal volumes showed no relationship with the DMN subsequent memory effect or mPerAF. Lastly, older adults with higher mPerAF in the DMN at rest tend to show higher memory performance, pointing towards the importance of a maintained ability to modulate DMN activity in old age.

Education differentiates cognitive performance and resting state fMRI connectivity in healthy aging

Objectives

In healthy aging, the way people cope differently with cognitive and neural decline is influenced by exposure to cognitively enriching life-experiences. Education is one of them, so that in general, the higher the education, the better the expected cognitive performance in aging. At the neural level, it is not clear yet how education can differentiate resting state functional connectivity profiles and their cognitive underpinnings. Thus, with this study, we aimed to investigate whether the variable education allowed for a finer description of age-related differences in cognition and resting state FC.

Methods

We analyzed in 197 healthy individuals (137 young adults aged 20-35 and 60 older adults aged 55-80 from the publicly available LEMON database), a pool of cognitive and neural variables, derived from magnetic resonance imaging, in relation to education. Firstly, we assessed age-related differences, by comparing young and older adults. Then, we investigated the possible role of education in outlining such differences, by splitting the group of older adults based on their education.

Results

In terms of cognitive performance, older adults with higher education and young adults were comparable in language and executive functions. Interestingly, they had a wider vocabulary compared to young adults and older adults with lower education. Concerning functional connectivity, the results showed significant age- and education-related differences within three networks: the Visual-Medial, the Dorsal Attentional, and the Default Mode network (DMN). For the DMN, we also found a relationship with memory performance, which strengthen the evidence that this network has a specific role in linking cognitive maintenance and FC at rest in healthy aging.

Discussion

Our study revealed that education contributes to differentiating cognitive and neural profiles in healthy older adults. Also, the DMN could be a key network in this context, as it may reflect some compensatory mechanisms relative to memory capacities in older adults with higher education.

Rescue of neurogenesis and age-associated cognitive decline in SAMP8 mouse: Role of transforming growth factor-alpha

Neuropathological aging is associated with memory impairment and cognitive decline, affecting several brain areas including the neurogenic niche of the dentate gyrus of the hippocampus (DG). In the healthy brain, homeostatic mechanisms regulate neurogenesis within the DG to facilitate the continuous generation of neurons from neural stem cells (NSC). Nevertheless, aging reduces the number of activated neural stem cells and diminishes the number of newly generated neurons. Strategies that promote neurogenesis in the DG may improve cognitive performance in the elderly resulting in the development of treatments to prevent the progression of neurological disorders in the aged population. Our work is aimed at discovering targeting molecules to be used in the design of pharmacological agents that prevent the neurological effects of brain aging. We study the effect of age on hippocampal neurogenesis using the SAMP8 mouse as a model of neuropathological aging. We show that in 6-month-old SAMP8 mice, episodic and spatial memory are impaired; concomitantly, the generation of neuroblasts and neurons is reduced and the generation of astrocytes is increased in this model. The novelty of our work resides in the fact that treatment of SAMP8 mice with a transforming growth factor-alpha (TGFα) targeting molecule prevents the observed defects, positively regulating neurogenesis and improving cognitive performance. This compound facilitates the release of TGFα in vitro and in vivo and activates signaling pathways initiated by this growth factor. We conclude that compounds of this kind that stimulate neurogenesis may be useful to counteract the neurological effects of pathological aging.

Reduced memory precision in older age is associated with functional and structural differences in the angular gyrus

Decreased fidelity of mnemonic representations plays a critical role in age-related episodic memory deficits, yet the brain mechanisms underlying such reductions remain unclear. Using functional and structural neuroimaging, we examined how changes in two key nodes of the posterior-medial network, the hippocampus and the angular gyrus (AG), might underpin loss of memory precision in older age. Healthy young and older adults completed a memory task that involved reconstructing object features on a continuous scale. Investigation of blood-oxygen-level-dependent (BOLD) activity during retrieval revealed an age-related reduction in activity reflecting successful recovery of object features in the hippocampus, whereas trial-wise modulation of BOLD signal by graded memory precision was diminished in the AG. Gray matter volume of the AG further predicted individual differences in memory precision in older age, beyond likelihood of successful retrieval. These findings provide converging evidence for a role of functional and structural integrity of the AG in constraining the fidelity of episodic remembering in older age, yielding new insights into parietal contributions to age-related episodic memory decline.

Individual differences in brain aging: heterogeneity in cortico-hippocampal but not caudate atrophy rates

It is well documented that some brain regions, such as association cortices, caudate, and hippocampus, are particularly prone to age-related atrophy, but it has been hypothesized that there are individual differences in atrophy profiles. Here, we document heterogeneity in regional-atrophy patterns using latent-profile analysis of 1,482 longitudinal magnetic resonance imaging observations. The results supported a 2-group solution reflecting differences in atrophy rates in cortical regions and hippocampus along with comparable caudate atrophy. The higher-atrophy group had the most marked atrophy in hippocampus and also lower episodic memory, and their normal caudate atrophy rate was accompanied by larger baseline volumes. Our findings support and refine models of heterogeneity in brain aging and suggest distinct mechanisms of atrophy in striatal versus hippocampal-cortical systems.

Older adults compensate for switch, but not mixing costs, relative to younger adults on an intrinsically cued task switching experiment

Introduction

Aging negatively impacts the ability to rapidly and successfully switch between two or more tasks that have different rules or objectives. However, previous work has shown that the context impacts the extent of this age-related impairment: while there is relative age-related invariance when participants must rapidly switch back and forth between two simple tasks (often called "switch costs"), age-related differences emerge when the contexts changes from one in which only one task must be performed to one in which multiple tasks must be performed, but a trial-level switch is not required (e.g., task repeat trials within dual task blocks, often called "mixing costs"). Here, we explored these two kinds of costs behaviorally, and also investigated the neural correlates of these effects.

Methods

Seventy-one younger adults and 175 older adults completed a task-switching experiment while they underwent fMRI brain imaging. We investigated the impact of age on behavioral performance and neural activity considering two types of potential costs: switch costs (dual-task switch trials minus dual-task non-switch trials), and mixing costs (dual-task non-switch minus single-task trials).

Results

We replicated previous behavioral findings, with greater age associated with mixing, but not switch costs. Neurally, we found age-related compensatory activations for switch costs in the dorsal lateral prefrontal cortex, pars opercularis, superior temporal gyrus, and the posterior and anterior cingulate, but age-related under recruitment for mixing costs in fronto-parietal areas including the supramarginal gyrus and pre and supplemental motor areas.

Discussion

These results suggest an age-based dissociation between executive components that contribute to task switching.

Widespread fMRI BOLD Signal Overactivations during Cognitive Control in Older Adults Are Not Matched by Corresponding Increases in fPET Glucose Metabolism

A common observation in fMRI studies using the BOLD signal is that older adults, compared with young adults, show overactivations, particularly during less demanding tasks. The neuronal underpinnings of such overactivations are not known, but a dominant view is that they are compensatory in nature and involve recruitment of additional neural resources. We scanned 23 young (20-37 years) and 34 older (65-86 years) healthy human adults of both sexes with hybrid positron emission tomography/MRI. The radioligand [18F]fluoro-deoxyglucose was used to assess dynamic changes in glucose metabolism as a marker of task-dependent synaptic activity, along with simultaneous fMRI BOLD imaging. Participants performed two verbal working memory (WM) tasks: one involving maintenance (easy) and one requiring manipulation (difficult) of information in WM. Converging activations to the WM tasks versus rest were observed for both imaging modalities and age groups in attentional, control, and sensorimotor networks. Upregulation of activity to WM-demand, comparing the more difficult to the easier task, also converged between both modalities and age groups. For regions in which older adults showed task-dependent BOLD overactivations compared with the young adults, no corresponding increases in glucose metabolism were found. To conclude, findings from the current study show that task-induced changes in the BOLD signal and synaptic activity as measured by glucose metabolism generally converge, but overactivations observed with fMRI in older adults are not coupled with increased synaptic activity, which suggests that these overactivations are not neuronal in origin.SIGNIFICANCE STATEMENT Findings of increased fMRI activations in older compared with younger adults have been suggested to reflect increased use of neuronal resources to cope with reduced brain function. The physiological underpinnings of such compensatory processes are poorly understood, however, and rest on the assumption that vascular signals accurately reflect neuronal activity. Comparing fMRI and simultaneously acquired functional positron emission tomography as an alternative index of synaptic activity, we show that age-related overactivations do not appear to be neuronal in origin. This result is important because mechanisms underlying compensatory processes in aging are potential targets for interventions aiming to prevent age-related cognitive decline.

Functional activity level reported by an informant is an early predictor of Alzheimer's disease

BACKGROUND

Loss of autonomy in day-to-day functioning is one of the feared outcomes of Alzheimer's disease (AD), and relatives may have been worried by subtle behavioral changes in ordinary life situations long before these changes are given medical attention. In the present study, we ask if such subtle changes should be given weight as an early predictor of a future AD diagnosis.

METHODS

Longitudinal data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) were used to define a group of adults with a mild cognitive impairment (MCI) diagnosis remaining stable across several visits (sMCI, n=360; 55-91 years at baseline), and a group of adults who over time converted from having an MCI diagnosis to an AD diagnosis (cAD, n=320; 55-88 years at baseline). Eleven features were used as input in a Random Forest (RF) binary classifier (sMCI vs. cAD) model. This model was tested on an unseen holdout part of the dataset, and further explored by three different permutation-driven importance estimates and a comprehensive post hoc machine learning exploration.

RESULTS

The results consistently showed that measures of daily life functioning, verbal memory function, and a volume measure of hippocampus were the most important predictors of conversion from an MCI to an AD diagnosis. Results from the RF classification model showed a prediction accuracy of around 70% in the test set. Importantly, the post hoc analyses showed that even subtle changes in everyday functioning noticed by a close informant put MCI patients at increased risk for being on a path toward the major cognitive impairment of an AD diagnosis.

CONCLUSION

The results showed that even subtle changes in everyday functioning should be noticed when reported by relatives in a clinical evaluation of patients with MCI. Information of these changes should also be included in future longitudinal studies to investigate different pathways from normal cognitive aging to the cognitive decline characterizing different stages of AD and other neurodegenerative disorders.

Brain reserve theory: Are adults with intellectual disability more vulnerable to age than peers with typical development?

BACKGROUND

Life expectancy is on rise and the intriguing question is: When does cognitive decline occur among adults with intellectual disability, compared to adults with typical development? This cross-sectional study examined cognitive performance of crystallised/fluid intelligence, working and long-term memory of adults with intellectual disability of etiologies other than Down syndrome (IQ 50-68) and adults with typical development (IQ 85-114) in four age cohorts (30-39; 40-49; 50-59; 60-69).

METHOD

The WAIS III^HEB and the Rey-AVLT were administered to both groups.

RESULTS

Four patterns of cognitive performance were found: (a) Vocabulary (crystallised intelligence), Spatial Span Forward and Retention yielded similar scores across all four age cohorts in participants with typical development and with intellectual disability. (b) Similarities, Raven and Digit Span Backward exhibit lower scores only in 50-59 or 60-69 compared to the 30-39 age cohort in both groups, (c) Digit Span Forward, Spatial Span Backward and Total Leaning (LTM) yielded lower scores in the 50-59 or 60-69 age cohorts in the typical group, but similar scores in participants with intellectual disability along the age cohorts, (d) Block Design (fluid intelligence) yielded a lower score in the 50-59 cohort versus lower scores only at ages 60-69 in participants with typical development.

CONCLUSIONS

Our findings suggest a possible parallel trajectory in age-related cognitive performance for individuals with and without intellectual disability in six measures, and a possible more preserved trajectory in fluid intelligence and some memory measures in adults with intellectual disability compared to their peers. Caution should be exercised regarding Digit and Spatial Span Backwards, which yielded a floor effect in participants with intellectual disability. The Cognitive Reserve Theory, the Safeguard Hypothesis and late maturation might serve as explanations for these findings.

Altered alpha/beta desynchronization during item-context binding contributes to the associative deficit in older age

It is proposed that older adults have difficulties to bind item and context and to recruit deep, elaborative processing during encoding. Senescent changes in the oscillatory foundations of these processes are currently unclear. We recorded electroencephalography during item-context memory formation in younger (n = 57) and older (n = 55) adults. At test, we assessed memory for the items and the item-context pairs and examined encoding-related activity based on how much information was recovered at retrieval (miss < item-only < pair). Item memory was comparable between age groups while pair memory was reduced in the older adults. Theta synchronization and alpha/beta desynchronization increased linearly with the amount of information available. Single-trial theta power could not predict subsequent item memory, but predicted pair memory in an age-invariant manner, in line with a mechanism supporting associative memory. In contrast, single-trial alpha/beta power predicted both item and pair memory, in line with a mechanism reflecting the depth of information processing, and predicted pair memory less well in the older than the younger adults. Thus, theta and alpha/beta oscillations contribute differently in shaping the contents of memories and reduced processing capacity contributes to episodic memory decline in older age.

Effects of breaking up sitting with light-intensity physical activity on cognition and mood in university students

BACKGROUND

University students often exhibit high levels of sedentary behavior that is negatively associated with cognition and mood. On the other hand, light-intensity physical activity (LIPA) may improve cognitive performance and mood. Therefore, this study investigated the acute effect of LIPA breaks during prolonged sitting on attention, executive functioning, and mood.

METHODS

A randomized crossover design was used in this study. In total, 21 healthy adults (15 women, age = 24 ± 3 years, BMI = 23 ± 2 kg/m² ) completed three prolonged sitting conditions: (1) without a demanding cognitive task (SIT), (2) with a demanding cognitive task (COGN), and (3) with every 25 min sitting interrupted by a 5-minute walk (INTERRUPT). Attention, executive function (response inhibition, task shifting, and working memory updating), and mood were assessed before and after each condition.

RESULTS

Linear mixed models analyses showed that prolonged sitting frequently interrupted by LIPA (INTERRUPT) or with cognitively demanding activities (COGN) significantly improved task shifting compared to SIT. However, INTERRUPT did not significantly improve task shifting compared with COGN. No significant acute effects on attention, response inhibition, working memory updating, or mood were found.

CONCLUSIONS

Frequent LIPA breaks or cognitively demanding activities have a selective, acute positive impact on one aspect of cognitive performance compared to idle sitting. No evidence was found that LIPA breaks have an acute improvement in attention, executive function, and mood compared to sitting with cognitive loading. To further investigate the effect of PA on cognitive performance, it is necessary to consider cognitive loading and control for the cognitive activity during sitting in the experimental design.

Predictors of longitudinal cognitive ageing from age 70 to 82 including APOE e4 status, early-life and lifestyle factors: the Lothian Birth Cohort 1936

Discovering why some people's cognitive abilities decline more than others is a key challenge for cognitive ageing research. The most effective strategy may be to address multiple risk factors from across the life-course simultaneously in relation to robust longitudinal cognitive data. We conducted a 12-year follow-up of 1091 (at age 70) men and women from the longitudinal Lothian Birth Cohort 1936 study. Comprehensive repeated cognitive measures of visuospatial ability, processing speed, memory, verbal ability, and a general cognitive factor were collected over five assessments (age 70, 73, 76, 79, and 82 years) and analysed using multivariate latent growth curve modelling. Fifteen life-course variables were used to predict variation in cognitive ability levels at age 70 and cognitive slopes from age 70 to 82. Only APOE e4 carrier status was found to be reliably informative of general- and domain-specific cognitive decline, despite there being many life-course correlates of cognitive level at age 70. APOE e4 carriers had significantly steeper slopes across all three fluid cognitive domains compared with non-carriers, especially for memory (β = -0.234, p < 0.001) and general cognitive function (β = -0.246, p < 0.001), denoting a widening gap in cognitive functioning with increasing age. Our findings suggest that when many other candidate predictors of cognitive ageing slope are entered en masse, their unique contributions account for relatively small proportions of variance, beyond variation in APOE e4 status. We conclude that APOE e4 status is important for identifying those at greater risk for accelerated cognitive ageing, even among ostensibly healthy individuals.

Early- to late-life environmental factors and late-life global cognition in septuagenarian and octogenarians: The SONIC study

This study aimed to evaluate cognitively stimulating environments throughout life and to examine direct and indirect associations between these environments and late-life cognition. Early-life education, three domains of work complexity (data, people, and things) based on the longest-held occupation, and engagement in late-life leisure activities (LAs) were assessed. A structural equation model was developed using cross-sectional data of 1721 Japanese older adults in 70 ± 1 and 80 ± 1 years. The model confirmed significant direct effects of work complexity with data and late-life LAs on late-life cognitive performance. The associations of education and work complexity with late-life cognition were mediated through the subsequent environment(s). However, the total effects of work complexity with people and things on late-life cognition were insignificant. The findings suggest that cognitively stimulating activities in adulthood and beyond may lead to individual differences in late-life global cognition. In addition, antecedent complex environments might make subsequent life environments more cognitively stimulating. The results are discussed from the perspectives of cognitive plasticity and environmental complexity.

Binding objects to their spatiotemporal context: Age gradient and neuropsychological correlates of What-Where-When task performance

A number of recent studies have shown that the ability to accurately recall bound object and spatiotemporal aspects of an experienced event develops gradually in children and is greatly impaired in the elderly, reflecting developmental discontinuities in the integrity of the underlying medial temporal lobe network. Using a novel What-Where-When (WWW) visuospatial reconstruction task, the experiential memory performance of a group of healthy older adults (aged 60-80) was compared to that of a group of younger adults (aged 20-40). Both groups were equated on their general cognitive ability, their executive functioning, and on the presence of depression, anxiety, and stress symptomatology. As hypothesized, the performance of the older adults in the binding task was significantly lower, with younger participants recalling three times the amount of bound object and spatiotemporal triads than their older counterparts. Psychomotor speed was found to be lower in older adults and was the only neuropsychological index to significantly affect success on the WWW binding task. Based on this and other relevant studies, the selective associative memory impairment obtained using a non-verbal What-Where-When paradigm emerges as a marker for the detection of early pre-clinical signs of experiential memory pathology.

The knowledge domain of cognitive neuroscience of aging: A Scientometric and bibliometric analysis

Cognitive neuroscience of aging (CNA) is a relatively young field compared with other branches of cognitive aging (CA). From the beginning of this century, scholars in CNA have contributed many valuable research to explain the cognitive ability decline in aging brains in terms of functional changes, neuromechanism, and neurodegenerative diseases. However, very few studies have systematically reviewed the research in the domain of CAN, with regard to its primary research topics, theories, findings, and future development. Therefore, this study used CiteSpace to conduct a bibliometric analysis of 1,462 published articles in CNA from Web of Science (WOS) and investigated the highly influential and potential research topics and theories of CNA, as well as important brain areas involved in CAN during 2000-2021. The results revealed that: (1) the research topics of "memory" and "attention" have been the focus of most studies, progressing into a fMRI-oriented stage; (2) the scaffolding theory and hemispheric asymmetry reduction in older adults model hold a key status in CNA, characterizing aging as a dynamic process and presenting compensatory relationships between different brain areas; and (3) age-related changes always occur in temporal (especially the hippocampus), parietal, and frontal lobes and the cognitive declines establish the compensation relationship between the anterior and posterior regions.

Cognitive interventions for memory and psychological well-being in aging and dementias

The human lifespan has expanded drastically in the last few centuries, due to improvements in sanitation, medicine, and nutrition, but with this increase in longevity comes higher rates of cognitive pathology such as mild cognitive impairment (MCI) and dementia; the latter is estimated to reach more than 75 million people by 2030. Pathology risk is related to measures of executive function, lifestyle factors (e.g., education, occupation, and leisure activities), and cognitive reserve. One way of building cognitive reserve may be to structure the environment to encourage lifelong engagement and learning, and since a pharmacological "cure" for dementia remains elusive, non-pharmacological approaches such as physical activity, social engagement, and cognitive stimulation are becoming increasingly essential to preserving and protecting brain health. Here, we describe our recent research into Reminiscence Therapy (RT) to promote cognitive and psychological function in old age and early dementia. We review the Recall Initiative, which involved brain imaging and behavioral indices of memory pre- and post-RT. We also report results from a pilot study-AIM WARM-in which RT was combined with physical activity, specifically walking, for early-stage dementia. Finally, we outline our future directions for tailored reminiscence interventions in combination with other activities (e.g., yoga and meditation) for different groups, namely early Alzheimer's disease, Semantic Dementia, and older individuals in the prison system.