Age-related differences in neural activity during memory encoding and retrieval: a positron emission tomography study

Mismatch negativity predicts age-related declines in memory precision

Does precision in auditory perception predict precision in subsequent memory (i.e., mnemonic discrimination) in aging? This study examined if the mismatch negativity (MMN), an electrophysiological marker of change detection and encoding, relates to age differences in mnemonic discrimination. The MMN was recorded in 92 adults (18-86 years, 47 females) in a passive oddball paradigm using tone sequences. Participants then completed a surprise recognition test for presented sequences (i.e., old targets) against novel sequences (i.e., similar lures and dissimilar foils). Across the adult lifespan, MMN amplitudes showed attenuation with increasing age, accompanied by worse performance discriminating targets from lures and foils. Across participants, smaller MMN amplitude predicted worse recognition performance. Notably, MMN amplitude partially explained age-related declines in target-lure discriminability, but not target-foil discriminability. Findings reinforce the MMN as a marker of mnemonic discrimination, and clarify how age-related declines in memory precision at retrieval may be explained by age differences at encoding.

Functional implications of age-related atrophy of the corpus callosum

The corpus callosum plays a critical role in inter-hemispheric communication by coordinating the transfer of sensory, motor, cognitive, and emotional information between the two hemispheres. However, as part of the normal aging process, the corpus callosum undergoes significant structural changes, including reductions in both its size and microstructural integrity. These age-related alterations can profoundly impact the brain's ability to coordinate functions across hemispheres, leading to a decline in various aspects of sensory processing, motor coordination, cognitive functioning, and emotional regulation. This review aims to synthesize current research on age-related changes in the corpus callosum, examining the regional differences in atrophy, its underlying causes, and its functional implications. By exploring these aspects, we seek to emphasize the clinical significance of corpus callosum degeneration and its impact on the quality of life in older adults, as well as the potential for early detection and targeted interventions to preserve brain health during aging. Finally, the review calls for further research into the mechanisms underlying corpus callosum atrophy and its broader implications for aging.

Combining non-invasive brain stimulation techniques and EEG markers analysis: an innovative approach to cognitive health in aging

In an era marked by a rapidly aging global population, delving into the intricate neurophysiological changes that accompany the aging process assumes paramount importance. This narrative review offers a comprehensive exploration of the intricate relationship between electromagnetic neuromodulation and electroencephalography (EEG) within the context of aging. Moreover, it showed the promising landscape of non-invasive neuromodulation techniques, encompassing established methodologies like transcranial magnetic stimulation (TMS) and transcranial direct and alternating current stimulation (tDCS/tACS). These modalities are analyzed for their potential to shape EEG marks in the aging population. These associations not only could broaden our understanding of the aging brain but could also suggest exciting scenarios for therapeutic interventions and cognitive enhancement among the elderly. Consequently, the comprehension of these mechanisms emerges as a critical key player for the development of precisely tailored interventions, aimed at mitigating age-associated cognitive decline and supporting robust brain health in the elderly.

Hemispheric organization of the brain and its prevailing impact on the neuropsychology of aging

Age differences in brain hemispheric asymmetry have figured prominently in the neuropsychology of aging. Here, a broad overview of these empirical and theoretical approaches is provided that dates back to the 1970s and continues to the present day. Methodological advances often brought new evidence to bear on older ideas and promoted the development of new ones. The deficit-focused hypothesis of accelerated right-hemisphere aging is reviewed first, followed by subsequent accounts pertaining to compensation, reserve, and their potential hemispheric underpinnings. Structural and functional neuroimaging reveal important and consistent age-related patterns, including indications of reduced brain asymmetry in older relative to younger adults. While not mutually exclusive, different neuropsychologic theories of aging offer divergent interpretations of such patterns, including age-related reductions in neural specificity (dedifferentiation) and age-related compensatory bilateral recruitment [e.g., Hemispheric Asymmetry Reduction in Older Adults (HAROLD); Compensation-Related Utilization of Neural Circuits Hypothesis (CRUNCH)]. Further, recent neurobehavioral evidence suggests that the right hemisphere plays a unique role in resisting the neurocognitive effects of aging via brain reserve. Future advances in human cognitive neuroscience, including neurostimulation methods for targeted interventions, along with analytic techniques informed by machine learning promise new insights into the neuropsychology of aging and the role of hemispheric processes in resilience and decline.

Assessing age-related changes in brain activity during isometric upper and lower limb force control tasks

Despite the widespread use of older adults (OA) as controls in movement disorder studies, the specific effects of aging on the neural control of upper and lower limb movements remain unclear. While functional MRI paradigms focusing on hand movements are widely used to investigate age-related brain changes, research on lower limb movements is limited due to technical challenges in an MRI environment. This study addressed this gap by examining both upper and lower limb movements in healthy young adults (YA) vs. OA. Sixteen YA and 20 OA, matched for sex, dominant side, and cognitive status, performed pinch grip and ankle dorsiflexion tasks, each requiring 15% of their maximum voluntary contraction. While both groups achieved the target force and exhibited similar force variability and accuracy, OA displayed distinct differences in force control dynamics, with a slower rate of force increase in the hand task and a greater rate of force decrease in the foot task. Imaging results revealed that OA exhibited more widespread activation, extending beyond brain regions typically involved in movement execution. In the hand task, OA showed increased activity in premotor and visuo-motor integration regions, as well as in the cerebellar hemispheres. During the foot task, OA engaged the cerebellar hemispheres more than YA. Collectively, results suggest that OA may recruit additional brain regions to manage motor tasks, possibly to achieve similar performance. Future longitudinal studies that track changes over time could help clarify if declines in motor performance lead to corresponding changes in brain activation.

Exploring the Relationship Between CAIDE Dementia Risk and EEG Signal Activity in a Healthy Population

BACKGROUND

Accounting for dementia risk factors is essential in identifying people who would benefit most from intervention programs. The CAIDE dementia risk score is commonly applied, but its link to brain function remains unclear. This study aims to determine whether the variation in this score is associated with neurophysiological changes and cognitive measures in normative individuals.

METHODS

The sample comprised 38 participants aged between 54 and 79 (M = 67.05; SD = 6.02). Data were collected using paper-and-pencil tests and electroencephalogram (EEG) recordings in the resting state, channels FP1 and FP2. The EEG signals were analyzed using Power Spectral Density (PSD)-based features.

RESULTS

The CAIDE score is positively correlated with the relative power activation of the θ band and negatively correlated with the MMSE cognitive test score, and MMSE variations align with those found in distributions of EEG-extracted PSD-based features.

CONCLUSIONS

The findings suggest that CAIDE scores can identify individuals without noticeable cognitive changes who already exhibit brain activity similar to that seen in people with dementia. They also contribute to the convergent validity between CAIDE and the risk of cognitive decline. This underscores the importance of early monitoring of these factors to reduce the incidence of dementia.

The Lifespan Trajectories of Brain Activities Related to Cognitive Control

Cognitive control plays a pivotal role in guiding human goal-directed behavior. While existing studies have documented an inverted U-shaped trajectory of cognitive control both behaviorally and anatomically, little is known about the corresponding changes in functional brain activation with age. To bridge this gap, we conducted a comprehensive meta-analysis of 129 neuroimaging studies using conflict tasks, encompassing 3,388 participants aged from 5 to 85 years old. We have three major findings: 1) The inverted U-shaped trajectory is the predominant pattern; 2) Cognitive control-related brain regions exhibit heterogeneous lifespan trajectories: the frontoparietal control network follows inverted U-shaped trajectories, peaking between 24 and 40 years, while the dorsal attention network demonstrates no clear trajectories; 3) Both the youth and the elderly show weaker brain activities and greater left laterality than young to middle-aged adults. These results reveal the lifespan trajectories of cognitive control, highlighting heterogeneous fluctuations in brain networks with age.

Lifespan differences in hippocampal subregion connectivity patterns during movie watching

Age-related episodic memory decline is attributed to functional alternations in the hippocampus. Less clear is how aging affects the functional connections of the hippocampus to the rest of the brain during episodic memory processing. We examined fMRI data from the CamCAN dataset, in which a large cohort of participants watched a movie (N = 643; 18-88 years), a proxy for naturalistic episodic memory encoding. We examined connectivity profiles across the lifespan both within the hippocampus (anterior, posterior), and between the hippocampal subregions and cortical networks. Aging was associated with reductions in contralateral (left, right) but not ipsilateral (anterior, posterior) hippocampal subregion connectivity. Aging was primarily associated with increased coupling between the anterior hippocampus and regions affiliated with Control, Dorsal Attention and Default Mode networks, yet decreased coupling between the posterior hippocampus and a selection of these regions. Differences in age-related hippocampal-cortical, but not within-hippocampus circuitry selectively predicted worse memory performance. Our findings comprehensively characterize hippocampal functional topography in relation to cognition in older age, suggesting that shifts in cortico-hippocampal connectivity may be sensitive markers of age-related episodic memory decline.

Brain activation patterns in patients with post-stroke cognitive impairment during working memory task: a functional near-infrared spectroscopy study

Objective

To explore the activation patterns in the frontal cortex of patients with post-stroke cognitive impairment during the execution of working memory tasks.

Methods

15 patients with post-stroke cognitive impairment, 17 patients without cognitive impairment, and 15 healthy controls of similar age and sex were included. All participants under-went immediate recall task testing and near-infrared spectroscopy imaging to measure frontal cortex activation during the task.

Results

The healthy control group performed the best in the immediate recall task, followed by the post-stroke non-cognitive impairment group. The post-stroke cognitive impairment group had the poorest performance. The near-infrared spectroscopy results revealed that during the immediate recall task, the healthy control group primarily activated the left frontal lobe region. In contrast, post-stroke patients exhibited reduced activation in the left frontal lobe and increased activation in the right frontal cortex, particularly in the right frontopolar and orbitofrontal regions, with the post-stroke cognitive impairment group displaying the most pronounced changes.

Conclusion

Patients with post-stroke cognitive impairment exhibit reduced activation in the left prefrontal cortex during the working memory tasks. They rely on compensatory activation in the right prefrontal cortex, particularly in the frontopolar and orbitofrontal cortex, to successfully complete the task.

Investigation of hemispheric asymmetry in Alzheimer's disease patients during resting state revealed BY fNIRS

Alzheimer's disease (AD) is characterized by the gradual deterioration of brain structures and changes in hemispheric asymmetry. Meanwhile, healthy aging is associated with a decrease in functional hemispheric asymmetry. In this study, functional connectivity analysis was used to compare the functional hemispheric asymmetry in eyes-open resting-state fNIRS data of 16 healthy elderly controls (mean age: 60.4 years, MMSE (Mini-Mental State Examination): 27.3 ± 2.52) and 14 Alzheimer's patients (mean age: 73.8 years, MMSE: 22 ± 4.32). Increased interhemispheric functional connectivity was found in the premotor cortex, supplementary motor cortex, primary motor cortex, inferior parietal cortex, primary somatosensory cortex, and supramarginal gyrus in the control group compared to the AD group. The study revealed that the control group had stronger interhemispheric connectivity, leading to a more significant decrease in hemispheric asymmetry than the AD group. The results show that there is a difference in interhemispheric functional connections at rest between the Alzheimer's group and the control group, suggesting that functional hemispheric asymmetry continues in Alzheimer's patients.

Gaze data of 4243 participants shows link between leftward and superior attention biases and age

Healthy individuals typically show more attention to the left than to the right (known as pseudoneglect), and to the upper than to the lower visual field (known as altitudinal pseudoneglect). These biases are thought to reflect asymmetries in neural processes. Attention biases have been used to investigate how these neural asymmetries change with age. However, inconsistent results have been reported regarding the presence and direction of age-related effects on horizontal and vertical attention biases. The observed inconsistencies may be due to insensitive measures and small sample sizes, that usually only feature extreme age groups. We investigated whether spatial attention biases, as indexed by gaze position during free viewing of a single image, are influenced by age. We analysed free-viewing data from 4,243 participants aged 5-65 years and found that attention biases shifted to the right and superior directions with increasing age. These findings are consistent with the idea of developing cerebral asymmetries with age and support the hypothesis of the origin of the leftward bias. Age modulations were found only for the first seven fixations, corresponding to the time window in which an absolute leftward bias in free viewing was previously observed. We interpret this as evidence that the horizontal and vertical attention biases are primarily present when orienting attention to a novel stimulus - and that age modulations of attention orienting are not global modulations of spatial attention. Taken together, our results suggest that attention orienting may be modulated by age and that cortical asymmetries may change with age.

Separating binding and retrieval of event files in older adults

In the literature on human action control, it is assumed that features of stimuli (S) and responses (R) are integrated into internal representations (so-called event files) that are involved in the execution of an action. Experimentally, the impact of this integration on action control is typically analyzed via S-R binding effects. Recent theorizing in the BRAC framework (Frings et al., 2020) suggests to disentangle the processes of S-R binding proper from S-R retrieval as two independent components contributing to S-R binding effects. Since the literature on age effects on S-R binding effects is scarce and does not provide information on whether the existing findings about the two processes can be generalized to older age groups, this is the first study addressing the effects of older age separately on S-R binding proper vs. S-R retrieval. In two established variants of S-R binding tasks (cumulative n = 262), we contrasted binding (by using a saliency manipulation at the time of binding proper) versus retrieval processes (by manipulating the onset of the distractor at the time of retrieval), replicating previous results in younger (18-30 years) and also in older healthy controls (50-70 years). We therefore found no evidence for age effects on S-R binding proper or S-R retrieval. We thus conclude that the processes contributing to S-R binding effects are - at least in the age groups analyzed in this study - robust and age-independent. STATEMENT OF SIGNIFICANCE: In human action control, binding proper and retrieval of features in stimulus-response episodes typically lead to so-called S-R binding effects. Against the background of recent theorizing, binding proper and retrieval should be studied independently. In this article, we ran a younger and an older age group and analyzed possible age-related differences in integration or retrieval. Both groups showed the expected pattern for binding and retrieval as expected from the literature.

Increased neural differentiation after a single session of aerobic exercise in older adults

Aging is associated with decreased cognitive function. One theory posits that this decline is in part due to multiple neural systems becoming dedifferentiated in older adults. Exercise is known to improve cognition in older adults, even after only a single session. We hypothesized that one mechanism of improvement is a redifferentiation of neural systems. We used a within-participant, cross-over design involving 2 sessions: either 30 minutes of aerobic exercise or 30 minutes of seated rest (n = 32; ages 55-81 years). Both functional Magnetic Resonance Imaging (fMRI) and Stroop performance were acquired soon after exercise and rest. We quantified neural differentiation via general heterogeneity regression. There were 3 prominent findings following the exercise. First, participants were better at reducing Stroop interference. Second, while there was greater neural differentiation within the hippocampal formation and cerebellum, there was lower neural differentiation within frontal cortices. Third, this greater neural differentiation in the cerebellum and temporal lobe was more pronounced in the older ages. These data suggest that exercise can induce greater neural differentiation in healthy aging.

Age differences in the neural processing of semantics, within and beyond the core semantic network

Aging is associated with functional activation changes in domain-specific regions and large-scale brain networks. This preregistered Functional magnetic resonance imaging (fMRI) study investigated these effects within the domain of semantic cognition. Participants completed 1 nonsemantic and 2 semantic tasks. We found no age differences in semantic activation in core semantic regions. However, the right inferior frontal gyrus showed difficulty-related increases in both age groups. This suggests that age-related upregulation of this area may be a compensatory response to increased processing demands. At a network level, older people showed more engagement in the default mode network and less in the executive multiple-demand network, aligning with older people's greater knowledge reserves and executive declines. In contrast, activation was age-invariant in semantic control regions. Finally, older adults showed reduced demand-related modulation of multiple-demand network activation in the nonsemantic task but not the semantic tasks. These findings provide a new perspective on the neural basis of semantic cognition in aging, suggesting that preserved function in specialized semantic networks may help to maintain semantic cognition in later life.

The Development of a Pilot App Targeting Short-Term and Prospective Memory in People Diagnosed with Dementia

BACKGROUND

According to the World Health Organization, people suffering from dementia exhibit a serious decline in various cognitive domains and especially in memory.

AIMS

This study aims to create a pilot computer app to enhance short-term memory and prospective memory in individuals with dementia using errorless learning based on their individualized needs.

METHODS

Fifteen dementia patients and matched controls, matched for age, sex, and education, were selected. Their daily routines were analyzed, and cognitive abilities were assessed using the MoCA test. Considering the participants' illness severity and daily needs, the pilot app was designed to aid in remembering daily tasks (taking medication and meals), object locations, and familiar faces and names.

RESULTS

An improvement in patients' short-term and prospective memory throughout the training sessions, but not in overall cognitive functioning was observed. A statistically significant difference between patients and healthy controls was indicated in their ability to retain information relevant to them in their short-term memory, or to remember to act in the future following schedules organized at present (p < 0.001).

CONCLUSION

This app appears beneficial for training dementia patients and healthy individuals in addressing memory challenges.

RECOMMENDATION

While the pilot app showed promise, further research with larger samples is recommended.

Age-Related Changes in Episodic Processing of Scenes: A Functional Activation and Connectivity Study

The posterior-to-anterior shift in aging (PASA) effect is seen as a compensatory model that enables older adults to meet increased cognitive demands to perform comparably as their young counterparts. However, empirical support for the PASA effect investigating age-related changes in the inferior frontal gyrus (IFG), hippocampus, and parahippocampus has yet to be established. 33 older adults and 48 young adults were administered tasks sensitive to novelty and relational processing of indoor/outdoor scenes in a 3-Tesla MRI scanner. Functional activation and connectivity analyses were applied to examine the age-related changes on the IFG, hippocampus, and parahippocampus among low/high-performing older adults and young adults. Significant parahippocampal activation was generally found in both older (high-performing) and young adults for novelty and relational processing of scenes. Younger adults had significantly greater IFG and parahippocampal activation than older adults, and greater parahippocampal activation compared to low-performing older adults for relational processing-providing partial support for the PASA model. Observations of significant functional connectivity within the medial temporal lobe and greater negative left IFG-right hippocampus/parahippocampus functional connectivity for young compared to low-performing older adults for relational processing also supports the PASA effect partially.

Semantic cognition in healthy ageing: Neural signatures of representation and control mechanisms in naming typical and atypical objects

Effective use of conceptual knowledge engages semantic representation and control processes to access information in a goal-driven manner. Neuropsychological findings of patients presenting either degraded knowledge (e.g., semantic dementia) or disrupted control (e.g., semantic aphasia) converge with neuroimaging evidence from young adults, and delineate the neural segregation of representation and control mechanisms. However, there is still scarce research on the neurofunctional underpinnings of such mechanisms in healthy ageing. To address this, we conducted an fMRI study, wherein young and older adults performed a covert naming task of typical and atypical objects. Three main age-related differences were found. As shown by age group and typicality interactions, older adults exhibited overactivation during naming of atypical (e.g., avocado) relative to typical concepts in brain regions associated to semantic representation, including anterior and medial portions of left temporal lobe (respectively, ATL and MTG). This provides evidence for the reorganization of neural activity in these brain regions contingent to the enrichment of semantic repositories in older ages. The medial orbitofrontal gyrus was also overactivated, indicating that the processing of atypical concepts (relative to typical items) taxes additional control resources in the elderly. Increased activation in the inferior frontal gyrus (IFG) was observed in naming typical items (relative to atypical ones), but only for young adults. This suggests that naming typical items (e.g., strawberry) taxes more on control processes in younger ages, presumably due to the semantic competition set by other items that share multiple features with the target (e.g., raspberry, blackberry, cherry). Together, these results reveal the dynamic nature of semantic control interplaying with conceptual representations as people grow older, by indicating that distinct neural bases uphold semantic performance from young to older ages. These findings may be explained by neural compensation mechanisms coming into play to support neurocognitive changes in healthy ageing.

Hemispheric Asymmetries of Individual Differences in Functional Connectivity

Resting-state fMRI studies have revealed that individuals exhibit stable, functionally meaningful divergences in large-scale network organization. The locations with strongest deviations (called network "variants") have a characteristic spatial distribution, with qualitative evidence from prior reports suggesting that this distribution differs across hemispheres. Hemispheric asymmetries can inform us on constraints guiding the development of these idiosyncratic regions. Here, we used data from the Human Connectome Project to systematically investigate hemispheric differences in network variants. Variants were significantly larger in the right hemisphere, particularly along the frontal operculum and medial frontal cortex. Variants in the left hemisphere appeared most commonly around the TPJ. We investigated how variant asymmetries vary by functional network and how they compare with typical network distributions. For some networks, variants seemingly increase group-average network asymmetries (e.g., the group-average language network is slightly bigger in the left hemisphere and variants also appeared more frequently in that hemisphere). For other networks, variants counter the group-average network asymmetries (e.g., the default mode network is slightly bigger in the left hemisphere, but variants were more frequent in the right hemisphere). Intriguingly, left- and right-handers differed in their network variant asymmetries for the cingulo-opercular and frontoparietal networks, suggesting that variant asymmetries are connected to lateralized traits. These findings demonstrate that idiosyncratic aspects of brain organization differ systematically across the hemispheres. We discuss how these asymmetries in brain organization may inform us on developmental constraints of network variants and how they may relate to functions differentially linked to the two hemispheres.

Aging alters across-hemisphere cortical dynamics during binaural temporal processing

Differences in the timing and intensity of sounds arriving at the two ears provide fundamental binaural cues that help us localize and segregate sounds in the environment. Neural encoding of these cues is commonly represented asymmetrically in the cortex with stronger activation in the hemisphere contralateral to the perceived spatial location. Although advancing age is known to degrade the perception of binaural cues, less is known about how the neural representation of such cues is impacted by age. Here, we use electroencephalography (EEG) to investigate age-related changes in the hemispheric distribution of interaural time difference (ITD) encoding based on cortical auditory evoked potentials (CAEPs) and derived binaural interaction component (BIC) measures in ten younger and ten older normal-hearing adults. Sensor-level analyses of the CAEP and BIC showed age-related differences in global field power, where older listeners had significantly larger responses than younger for both binaural metrics. Source-level analyses showed hemispheric differences in auditory cortex activity for left and right lateralized stimuli in younger adults, consistent with a contralateral activation model for processing ITDs. Older adults, however, showed reduced hemispheric asymmetry across ITDs, despite having overall larger responses than younger adults. Further, when averaged across ITD condition to evaluate changes in cortical asymmetry over time, there was a significant shift in laterality corresponding to the peak components (P1, N1, P2) in the source waveform that also was affected by age. These novel results demonstrate across-hemisphere cortical dynamics during binaural temporal processing that are altered with advancing age.

The Overview of Cognitive Aging Models

To understand the cause of the age-related decline in cognitive function and its underlying mechanism, the cognitive aging model can provide us with important insights. In this section, we will introduce behavioral and neural models about age-related cognitive changes. Among behavioral models, several aging theories were discussed from the perspectives of educational, biological, and sociological factors, which could explain parts of the aging process. With the development of imaging technology, many studies have discussed the neural mechanism of aging and successively proposed neural models to explain the aging phenomenon. Behavioral models and neural mechanism models supplement each other, gradually unveiling the mystery of cognitive aging.

Interactions between the aging brain and motor task complexity across the lifespan: balancing brain activity resource demand and supply

The Compensation Related Utilization of Neural Circuits Hypothesis (CRUNCH) proposes a framework for understanding task-related brain activity changes as a function of healthy aging and task complexity. Specifically, it affords the following predictions: (i) all adult age groups display more brain activation with increases in task complexity, (ii) older adults show more brain activation compared with younger adults at low task complexity levels, and (iii) disproportionately increase brain activation with increased task complexity, but (iv) show smaller (or no) increases in brain activation at the highest complexity levels. To test these hypotheses, performance on a bimanual tracking task at 4 complexity levels and associated brain activation were assessed in 3 age groups (20-40, 40-60, and 60-80 years, n = 99). All age groups showed decreased tracking accuracy and increased brain activation with increased task complexity, with larger performance decrements and activation increases in the older age groups. Older adults exhibited increased brain activation at a lower complexity level, but not the predicted failure to further increase brain activity at the highest complexity level. We conclude that older adults show more brain activation than younger adults and preserve the capacity to deploy increased neural resources as a function of task demand.

Effects of age on the neural correlates of encoding source and item information: An fMRI study

The effects of age on encoding-related neural activity predictive of accurate item and source memory judgments were examined with fMRI, with an a priori focus of the inferior frontal gyrus (IFG) and hippocampus. During a scanned study phase, young and older adults viewed a series of pictures of objects and made one of two judgments on each object. At test, which occurred outside of the scanner, an 'old/new' judgment on each test item was followed, for those items endorsed old, by a source judgment querying the study task. Neural activity predictive of accurate subsequent item and source memory judgments was identified in bilateral IFG, several other cortical regions and bilateral hippocampus. Cortical effects were graded in the young group (source > item > miss) but predicted item memory only in the older group. Hippocampal effects exclusively predicted source memory, and the magnitude of these effects did not reliably differ between the age groups. In the older group only, IFG and hippocampal encoding effects were positively correlated across participants with memory performance. Similar findings were evident in the extra-IFG regions demonstrating encoding effects. With the exception of the age-dependent relationship identified for hippocampal encoding effects, the present findings are broadly consistent with those from prior aging studies that employed verbal memoranda and tests of associative recognition. Thus, they extend these prior findings to include non-verbal materials and a different operationalization of episodic recollection. Additionally, the present findings suggest that the sensitivity in older adults of IFG encoding effects to subsequent memory performance reflects a more general tendency for cortical encoding effects to predict memory performance in this age group.

Simulating the situated-self drives hippocampo-cortical engagement during inner narration of events

We often use inner narration when thinking about past and future events. The present paradigm explicitly addresses the influence of the language used in inner narration on the hippocampus-dependent event construction process. We assessed the language context effect during the inner narration of different event types: past, future, daydream, and self-unrelated fictitious events. The language context was assessed via a fluent bilingual population who used inner narration, either in their first language (L1) or second language (L2). Not all inner narration of events elicited hippocampo-cortical activity. In fact, only the angular gyrus and precuneus-retrosplenial cortex were activated by inner narration across all event types. More precisely, only inner narration of events which entailed the simulation of bodily self-location in space (whether or not they were time-marked: past, future, daydream) depended on the hippocampo-cortical system, while inner narration of events that did not entail bodily self-location (self-unrelated fictitious) did not. The language context of the narration influenced the bilinguals' hippocampo-cortical system by enhancing the co-activation of semantic areas with the hippocampus for inner narration of events in the L2. Overall, this study highlights 2 important characteristics of hippocampo-cortical-dependent inner narration of events: The core episodic hippocampal system is activated for inner narration of events simulating self-location in space (regardless of time-marking), and the inner language used for narration (L1 or L2) mediates hippocampal functional connectivity.

Coupling of sensorimotor and cognitive functions in middle- and late adulthood

Introduction

The present study explored age effects and the coupling of sensorimotor and cognitive functions in a stratified sample of 96 middle-aged and older adults (age 45-86 years) with no indication of mild cognitive decline. In our sensorimotor tasks, we had an emphasis on listening in noise and postural control, but we also assessed functional mobility and tactile sensitivity.

Methods

Our cognitive measures comprised processing speed and assessments of core cognitive control processes (executive functions), notably inhibition, task switching, and working memory updating. We explored whether our measures of sensorimotor functioning mediated age differences in cognitive variables and compared their effect to processing speed. Subsequently, we examined whether individuals who had poorer (or better) than median cognitive performance for their age group also performed relatively poorer (or better) on sensorimotor tasks. Moreover, we examined whether the link between cognitive and sensorimotor functions becomes more pronounced in older age groups.

Results

Except for tactile sensitivity, we observed substantial age-related differences in all sensorimotor and cognitive variables from middle age onward. Processing speed and functional mobility were reliable mediators of age in task switching and inhibitory control. Regarding coupling between sensorimotor and cognition, we observed that individuals with poor cognitive control do not necessarily have poor listening in noise skills or poor postural control.

Discussion

As most conditions do not show an interdependency between sensorimotor and cognitive performance, other domain-specific factors that were not accounted for must also play a role. These need to be researched in order to gain a better understanding of how rehabilitation may impact cognitive functioning in aging persons.

Opportunities to Discuss Diversity-Related Topics in Neuroscience Courses

Diversity is a foundational topic in psychology, and APA recommends that diversity is covered across the psychology curriculum. Neuroscience courses face challenges with incorporating diversity-related topics owing to the historical lack of neuroscience research that focuses on diversity and the restricted range of diversity-related topics that neuroscience is typically associated with (i.e., health and disability status). This may limit students' learning of neuroscience's contributions towards understanding diversity. We review some specific examples of diversity-related topics that can be incorporated into neuroscience courses. These examples have been selected to include topics across the three major content domains of neuroscience (cellular/molecular, neuroanatomy/systems, and cognitive/behavioral), as well as across multiple diversity-related topics. Neuroscience instructors can use these examples to incorporate greater coverage of diversity-related topics within their courses and/or as points of inspiration for their own curricular additions. Providing systematic coverage of diversity-related topics in neuroscience courses highlights the ways neuroscience advances our understanding of human diversity and contributes to the educational objectives of psychology and neuroscience programs.

25 years of neurocognitive aging theories: What have we learned?

The past 25 years have provided a rich discovery of at least four fundamental patterns that represent structural and functional brain aging across multiple cognitive domains. Of the many potential patterns of brain aging, few are ever examined simultaneously in a given study, leading one to question their mutual exclusivity. Moreover, more studies are emerging that note failures to replicate some brain aging patterns, thereby questioning the universality and prevalence of these patterns. Although some attempts have been made to create unifying theories incorporating many of these age-related brain patterns, we propose that the field’s understanding of the aging brain has been hindered due to a large number of influential models with little crosstalk between them. We briefly review these brain patterns, the influential domain-general theories of neurocognitive aging that attempt to explain them, and provide examples of recent challenges to these theories. Lastly, we elaborate on improvements that can be made to lead the field to more comprehensive and robust models of neurocognitive aging.

A healthy mind in a healthy body: Effects of arteriosclerosis and other risk factors on cognitive aging and dementia

In this review we start from the assumption that, to fully understand cognitive aging, it is important to embrace a holistic view, integrating changes in bodily, brain, and cognitive functions. This broad view can help explain individual differences in aging trajectories and could ultimately enable prevention and remediation strategies. As the title of this review suggests, we claim that there are not only indirect but also direct effects of various organ systems on the brain, creating cascades of phenomena that strongly contribute to age-related cognitive decline. Here we focus primarily on the cerebrovascular system, because of its direct effects on brain health and close connections with the development and progression of Alzheimer's Disease and other types of dementia. We start by reviewing the main cognitive changes that are often observed in normally aging older adults, as well as the brain systems that support them. Second, we provide a brief overview of the cerebrovascular system and its known effects on brain anatomy and function, with a focus on aging. Third, we review genetic and lifestyle risk factors that may affect the cerebrovascular system and ultimately contribute to cognitive decline. Lastly, we discuss this evidence, review limitations, and point out avenues for additional research and clinical intervention.

Power shift and connectivity changes in healthy aging during resting-state EEG

The neural activity of human brain changes in healthy individuals during aging. The most frequent variation in patterns of neural activity are a shift from posterior to anterior areas and a reduced asymmetry between hemispheres. These patterns are typically observed during task execution and by using functional magnetic resonance imaging data. In the present study we investigated whether analogous effects can also be detected during rest and by means of source-space time series reconstructed from electroencephalographic recordings. By analyzing oscillatory power distribution across the brain we indeed found a shift from posterior to anterior areas in older adults. We additionally examined this shift by evaluating connectivity and its changes with age. The findings indicated that inter-area connections among frontal, parietal and temporal areas were strengthened in older individuals. A more complex pattern was shown in intra-area connections, where age-related activity was enhanced in parietal and temporal areas, and reduced in frontal areas. Finally, the resulting network exhibits a loss of modularity with age. Overall, the results extend to resting-state condition the evidence of an age-related shift of brain activity from posterior to anterior areas, thus suggesting that this shift is a general feature of the aging brain rather than being task-specific. In addition, the connectivity results provide new information on the reorganization of resting-state brain activity in aging.

Bridging patterns of neurocognitive aging across the older adult lifespan

Magnetic resonance imaging (MRI) studies of brain and neurocognitive aging rarely include oldest-old adults (ages 80 +). But predictions of neurocognitive aging theories derived from MRI findings in younger-old adults (ages ~55-80) may not generalize into advanced age, particularly given the increased prevalence of cognitive impairment/dementia in the oldest-old. Here, we reviewed the MRI literature in oldest-old adults and interpreted findings within the context of regional variation, compensation, brain maintenance, and reserve theories. Structural MRI studies revealed regional variation in brain aging as larger age effects on medial temporal and posterior regions for oldest-old than younger-old adults. They also revealed that brain maintenance explained preserved cognitive functioning into the tenth decade of life. Very few functional MRI studies examined compensatory activity in oldest-old adults who perform as well as younger groups, although there was evidence that higher brain reserve in oldest-old adults may mediate effects of brain aging on cognition. Despite some continuity, different cognitive and neural profiles across the older adult lifespan should be addressed in modern neurocognitive aging theories.

Overview of (f)MRI Studies of Cognitive Aging for Non-Experts: Looking through the Lens of Neuroimaging

This special issue concerning Brain Functional and Structural Connectivity and Cognition aims to expand our understanding of brain connectivity. Herein, I review related topics including the principle and concepts of functional MRI, brain activation, and functional/structural connectivity in aging for uninitiated readers. Visuospatial attention, one of the well-studied functions in aging, is discussed from the perspective of neuroimaging.

Inter- and Intra-Hemispheric Age-Related Remodeling in Visuo-Spatial Working Memory

Electroencephalography (EEG) studies investigating visuo-spatial working memory (vWM) in aging typically adopt an event-related potential (ERP) analysis approach that has shed light on the age-related changes during item retention and retrieval. However, this approach does not fully enable a detailed description of the time course of the neural dynamics related to aging. The most frequent age-related changes in brain activity have been described by two influential models of neurocognitive aging, the Hemispheric Asymmetry Reduction in Older Adults (HAROLD) and the Posterior-Anterior Shift in Aging (PASA). These models posit that older adults tend to recruit additional brain areas (bilateral as predicted by HAROLD and anterior as predicted by PASA) when performing several cognitive tasks. We tested younger (N = 36) and older adults (N = 35) in a typical vWM task (delayed match-to-sample) where participants have to retain items and then compare them to a sample. Through a data-driven whole scalp EEG analysis we aimed at characterizing the temporal dynamics of the age-related activations predicted by the two models, both across and within different stages of stimulus processing. Behaviorally, younger outperformed older adults. The EEG analysis showed that older adults engaged supplementary bilateral posterior and frontal sites when processing different levels of memory load, in line with both HAROLD and PASA-like activations. Interestingly, these age-related supplementary activations dynamically developed over time. Indeed, they varied across different stages of stimulus processing, with HAROLD-like modulations being mainly present during item retention, and PASA-like activity during both retention and retrieval. Overall, the present results suggest that age-related neural changes are not a phenomenon indiscriminately present throughout all levels of cognitive processing.

Differences in Diffusion Tensor Imaging White Matter Integrity Related to Verbal Fluency Between Young and Old Adults

Throughout adulthood, the brain undergoes an array of structural and functional changes during the typical aging process. These changes involve decreased brain volume, reduced synaptic density, and alterations in white matter (WM). Although there have been some previous neuroimaging studies that have measured the ability of adult language production and its correlations to brain function, structural gray matter volume, and functional differences between young and old adults, the structural role of WM in adult language production in individuals across the life span remains to be thoroughly elucidated. This study selected 38 young adults and 35 old adults for diffusion tensor imaging (DTI) and performed the Controlled Oral Word Association Test to assess verbal fluency (VF). Tract-Based Spatial Statistics were employed to evaluate the voxel-based group differences of diffusion metrics for the values of fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD), and local diffusion homogeneity (LDH) in 12 WM regions of interest associated with language production. To investigate group differences on each DTI metric, an analysis of covariance (ANCOVA) controlling for sex and education level was performed, and the statistical threshold was considered at p < 0.00083 (0.05/60 labels) after Bonferroni correction for multiple comparisons. Significant differences in DTI metrics identified in the ANCOVA were used to perform correlation analyses with VF scores. Compared to the old adults, the young adults had significantly (1) increased FA values on the bilateral anterior corona radiata (ACR); (2) decreased MD values on the right ACR, but increased MD on the left uncinate fasciculus (UF); and (3) decreased RD on the bilateral ACR. There were no significant differences between the groups for AD or LDH. Moreover, the old adults had only a significant correlation between the VF score and the MD on the left UF. There were no significant correlations between VF score and DTI metrics in the young adults. This study adds to the growing body of research that WM areas involved in language production are sensitive to aging.

How the healthy ageing brain supports semantic binding during language comprehension

Semantic binding refers to constructing complex meaning based on elementary building blocks. Using electroencephalography (EEG), we investigated the age-related changes in modulations of oscillatory brain activity supporting lexical retrieval and semantic binding. Young and older adult participants were visually presented two-word phrases, which for the first word revealed a lexical retrieval signature (e.g., swift vs. swrfeq) and for the second word revealed a semantic binding signature (e.g., horse in a semantic binding "swift horse" vs. no binding "swrfeq horse" context). The oscillatory brain activity associated with lexical retrieval as well as semantic binding significantly differed between healthy older and young adults. Specifically for lexical retrieval, we found that different age groups exhibited opposite patterns of theta and alpha modulation, which as a combined picture suggest that lexical retrieval is associated with different and delayed signatures in older compared with young adults. For semantic binding, in young adults, we found a signature in the low-beta range centred around the target word onset (i.e., a smaller low-beta increase for binding relative to no binding), whereas in healthy older adults, we found an opposite binding signature about ~500 ms later in the low- and high-beta range (i.e., a smaller low- and high-beta decrease for binding relative to no binding). The novel finding of a different and delayed oscillatory signature for semantic binding in healthy older adults reflects that the integration of word meaning into the semantic context takes longer and relies on different mechanisms in healthy older compared with young adults.

Semantic Congruence Drives Long-Term Memory and Similarly Affects Neural Retrieval Dynamics in Young and Older Adults

Learning novel information can be promoted if it is congruent with already stored knowledge. This so-called semantic congruence effect has been broadly studied in healthy young adults with a focus on neural encoding mechanisms. However, the impacts on retrieval, and possible impairments during healthy aging, which is typically associated with changes in declarative long-term memory, remain unclear. To investigate these issues, we used a previously established paradigm in healthy young and older humans with a focus on the neural activity at a final retrieval stage as measured with electroencephalography (EEG). In both age groups, semantic congruence at encoding enhanced subsequent long-term recognition memory of words. Compatible with this observation, semantic congruence led to differences in event-related potentials (ERPs) at retrieval, and this effect was not modulated by age. Specifically, congruence modulated old/new ERPs at a fronto-central (Fz) and left parietal (P3) electrode in a late (400–600 ms) time window, which has previously been associated with recognition memory processes. Importantly, ERPs to old items also correlated with the positive effect of semantic congruence on long-term memory independent of age. Together, our findings suggest that semantic congruence drives subsequent recognition memory across the lifespan through changes in neural retrieval processes.

Age-Related Changes in Hemispherical Specialization for Attentional Networks

Many cognitive functions face a decline in the healthy elderly. Within the cognitive domains, both attentional processes and executive functions are impaired with aging. Attention includes three attentional networks, i.e., alerting, orienting, and executive control, showing a hemispheric lateralized pattern in adults. This lateralized pattern could play a role in modulating the efficiency of attentional networks. For these reasons, it could be relevant to analyze the age-related change of the hemispheric specialization of attentional networks. This study aims to clarify this aspect with a lateralized version of the Attentional Network Test for Interaction (ANTI)-Fruit. One hundred seventy-one participants took part in this study. They were divided in three age groups: youth (N = 57; range: 20-30); adults (N = 57; range 31-64), and elderly/older people (N = 57; range: 65-87). The results confirmed the previous outcomes on the efficiency and interactions among attentional networks. Moreover, an age-related generalized slowness was evidenced. These findings also support the hypothesis of a hemispheric asymmetry reduction in elderly/older adults.

Comparison of exergames versus conventional exercises on the cognitive skills of older adults: a systematic review with meta-analysis

PURPOSE

To compare the effects of exergames versus conventional physical training on the cognitive skills of older adults.

MATERIALS AND METHODS

Scientific studies published in PubMed, Web of Science, and Cochrane Library databases were searched. Individual studies were assessed using the Cochrane Risk-of-bias tool for randomized trials (RoB 2). The quality of evidence was evaluated using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE Pro). The cognitive outcomes were Trail Making Test (TMT)-A, TMT-B, Stroop Word-Color test, Mini Mental State Examination (MMSE), and Montreal Cognitive Assessment (MoCA).

RESULTS

We identified 256 studies, in which 13 studies were included in the systematic review and 11 in the meta-analysis. The majority of the exergame interventions were based on the Xbox 360's Kinect, followed by the Impact Dance Platform, Nintendo Wii, and the Bike Labyrinth. We observed heterogeneity in the conventional exercise group and in the duration of training, which ranged from 12 to 52 sessions. There was no statistically significant difference between groups in TMT-A (p=0.083), TMT-B (p=0.122), and Stroop (p=0.191). There were differences in favor of exergames in MMSE (raw mean difference=-1.58, 95% CI: -2.87 to -0.28, p<0.001) and MoCA (raw mean difference=-1.22, 95% CI: -2.24 to -0.20, p=0.019).

CONCLUSIONS

Despite statistical differences in MMSE and MoCA, these results should be interpreted with caution due to methodological heterogeneity. Some studies reported possible neurophysiological benefits induced by exergames, which should be explored in future investigations.

Age-Related Differences in Functional Asymmetry During Memory Retrieval Revisited: No Evidence for Contralateral Overactivation or Compensation

Brain asymmetry is inherent to cognitive processing and seems to reflect processing efficiency. Lower frontal asymmetry is often observed in older adults during memory retrieval, yet it is unclear whether lower asymmetry implies an age-related increase in contralateral recruitment, whether less asymmetry reflects compensation, is limited to frontal regions, or predicts neurocognitive stability or decline. We assessed age-related differences in asymmetry across the entire cerebral cortex, using functional magnetic resonance imaging data from 89 young and 76 older adults during successful retrieval, and surface-based methods allowing direct homotopic comparison of activity between cortical hemispheres . An extensive left-asymmetric network facilitated retrieval in both young and older adults, whereas diverse frontal and parietal regions exhibited lower asymmetry in older adults. However, lower asymmetry was not associated with age-related increases in contralateral recruitment but primarily reflected either less deactivation in contralateral regions reliably signaling retrieval failure in the young or lower recruitment of the dominant hemisphere-suggesting that functional deficits may drive lower asymmetry in older brains, not compensatory activity. Lower asymmetry predicted neither current memory performance nor the extent of memory change across the preceding ~ 8 years in older adults. Together, these findings are inconsistent with a compensation account for lower asymmetry during retrieval and aging.

The Effects of Amyloid and Tau on Functional Network Connectivity in Older Populations

Background: Neuroimaging studies suggest that aged brains show altered connectivity within and across functional networks. Similar changes in functional network integrity are also linked to the accumulation of pathological proteins in the brain, such as amyloid-beta plaques and neurofibrillary tau tangles seen in Alzheimer's disease. However, less is known about the specific impacts of amyloid and tau on functional network connectivity in cognitively normal older adults who harbor these proteins. Methods: We briefly summarize recent neuroimaging studies of aging and then thoroughly review positron emission tomography and functional magnetic resonance imaging studies measuring the relationship between amyloid-tau pathology and functional connectivity in cognitively normal older individuals. Results: The literature overall suggests that amyloid-positive older individuals show minor cognitive dysfunction and aberrant default mode network connectivity compared with amyloid-negative individuals. Tau, however, is more closely associated with network hypoconnectivity and poorer cognition. Those with substantial amyloid and tau experience even greater cognitive decline compared with those with primarily amyloid or tau, suggesting a potential interaction. Multimodal neuroimaging studies suggest that older adults with pathological protein deposits show amyloid-related hyperconnectivity and tau-related hypoconnectivity in multiple functional networks, including the default mode and frontoparietal networks. Discussion: We propose an updated model considering the effects of amyloid and tau on functional connectivity in older individuals. Large, longitudinal neuroimaging studies with multiple levels of analysis are required to obtain a deeper understanding of the dynamic relationship between pathological protein accumulation and functional connectivity changes, as amyloid- and tau-induced connectivity alterations may have critical and time-varying effects on neurodegeneration and cognitive decline. Impact statement Amyloid and tau accumulation have been linked with altered functional connectivity in cognitively normal older adults. This review synthesized recent functional imaging literatures in a discussion of how amyloid and tau can interactively affect functional connectivity in nonlinear ways, which can explain previous conflicting findings. Changes in connectivity strength may depend on the accumulation of both amyloid and tau, and their integrative effects seem to have critical consequences on cognition. Elucidating the effects of these pathological proteins on brain functioning is paramount to understand the etiology of Alzheimer's disease and the aging process overall.

Stimulus transformation into motor action: Dynamic graph analysis reveals a posterior-to-anterior shift in brain network communication of older subjects

Cognitive performance slows down with increasing age. This includes cognitive processes that are essential for the performance of a motor act, such as the slowing down in response to an external stimulus. The objective of this study was to identify aging-associated functional changes in the brain networks that are involved in the transformation of external stimuli into motor action. To investigate this topic, we employed dynamic graphs based on phase-locking of Electroencephalography signals recorded from healthy younger and older subjects while performing a simple visually-cued finger-tapping task. The network analysis yielded specific age-related network structures varying in time in the low frequencies (2-7 Hz), which are closely connected to stimulus processing, movement initiation and execution in both age groups. The networks in older subjects, however, contained several additional, particularly interhemispheric, connections and showed an overall increased coupling density. Cluster analyses revealed reduced variability of the subnetworks in older subjects, particularly during movement preparation. In younger subjects, occipital, parietal, sensorimotor and central regions were-temporally arranged in this order-heavily involved in hub nodes. Whereas in older subjects, a hub in frontal regions preceded the noticeably delayed occurrence of sensorimotor hubs, indicating different neural information processing in older subjects. All observed changes in brain network organization, which are based on neural synchronization in the low frequencies, provide a possible neural mechanism underlying previous fMRI data, which report an overactivation, especially in the prefrontal and pre-motor areas, associated with a loss of hemispheric lateralization in older subjects.

Age-related effects on the neural processing of semantic complexity in a continuous narrative: Modulation by gestures already present in young to middle-aged adults

The processing of semantically complex speech is a demanding task which can be facilitated by speech-associated arm and hand gestures. However, the role of age concerning the perception of semantic complexity and the influence of gestures in this context remains unclear. The goal of this study was to investigate if age-related differences are already present in early adulthood during the processing of semantic complexity and gestures. To this end, we analyzed fMRI images of a sample of 38 young and middle-aged participants (age-range: 19-55). They had the task to listen and to watch a narrative. The narrative contained segments varying in the degree of semantic complexity, and they were spontaneously accompanied by gestures. The semantic complexity of the story was measured by the idea density. Consistent with previous findings in young adults, we observed increased activation for passages with lower compared to higher complexity in bilateral temporal areas and the precuneus. BOLD signal in the left frontal and left parietal regions correlated during the perception of complex passages with increasing age. This correlation was reduced for passages presented with gestures. Median-split based post-hoc comparisons confirmed that group differences between younger (19-23 years) and older adults within the early adult lifespan (24-55 years) were significantly reduced in passages with gestures. Our results suggest that older adults within early adulthood adapt to the requirements of highly complex passages activating additional regions when no gesture information is available. Gestures might play a facilitative role with increasing age, especially when speech is complex.

Acting Before; A Combined Strategy to Counteract the Onset and Progression of Dementia

Brain aging and aging-related neurodegenerative disorders are posing a significant challenge for health systems worldwide. To date, most of the therapeutic efforts aimed at counteracting dementiarelated behavioral and cognitive impairment have been focused on addressing putative determinants of the disease, such as β-amyloid or tau. In contrast, relatively little attention has been paid to pharmacological interventions aimed at restoring or promoting the synaptic plasticity of the aging brain. The review will explore and discuss the most recent molecular, structural/functional, and behavioral evidence that supports the use of non-pharmacological approaches as well as cognitive-enhancing drugs to counteract brain aging and early-stage dementia.

Biological and environmental predictors of heterogeneity in neurocognitive ageing: Evidence from Betula and other longitudinal studies

Individual differences in cognitive performance increase with advancing age, reflecting marked cognitive changes in some individuals along with little or no change in others. Genetic and lifestyle factors are assumed to influence cognitive performance in ageing by affecting the magnitude and extent of age-related brain changes (i.e., brain maintenance or atrophy), as well as the ability to recruit compensatory processes. The purpose of this review is to present findings from the Betula study and other longitudinal studies, with a focus on clarifying the role of key biological and environmental factors assumed to underlie individual differences in brain and cognitive ageing. We discuss the vital importance of sampling, analytic methods, consideration of non-ignorable dropout, and related issues for valid conclusions on factors that influence healthy neurocognitive ageing.

Age-related prefrontal cortex activation in associative memory: An fNIRS pilot study

Older adults typically perform more poorly than younger adults in free recall memory tests. This age-related deficit has been linked to decline of brain activation and brain prefrontal lateralization, which may be the result of compensatory mechanisms. In the present pilot study, we investigated the effect of age on prefrontal cortex (PFC) activation during performance of a task that requires memory associations (temporal vs. spatial clustering), using functional Near-Infrared Spectroscopy (fNIRS). Ten younger adults, ten cognitively high-performing older individuals, and ten low-performing older individuals completed a free recall task, where either a temporal or spatial strategy (but not both simultaneously) could be employed to retrieve groups of same-category stimuli, whilst changes in PFC hemodynamics were recorded by means of a 12-channel fNIRS system. The results suggest PFC activation, and right lateralization specific to younger adults. Moreover, age did not affect use of memory organization, given that temporal clustering was preferred over spatial clustering in all groups. These findings are in line with previous literature on the aging brain and on temporal organization of memory. Our results also suggest that the PFC may be specifically involved in memory for temporal associations. Future research may consider whether age-related deficits in temporal organization may be an early sign of PFC pathology and possible neurodegeneration.

Episodic memory for visual scenes suggests compensatory brain activity in breast cancer patients: a prospective longitudinal fMRI study

It has been hypothesized that breast cancer and its chemotherapy can impart functional neural changes via an overlap with biological mechanisms associated with aging. Here we used fMRI to assess whether changes in neural activity accompanying visual episodic memory encoding and retrieval suggest altered activations according to patterns seen in functional imaging of cognitive aging. In a prospective longitudinal design, breast cancer patients (n = 13) were scanned during memory encoding and retrieval before and after chemotherapy treatment, and compared to healthy-age matched controls (n = 13). Our results indicate that despite equivalent behavioral performance, encoding and retrieval resulted in increased activation of prefrontal regions for the breast cancer group compared to controls for both before and after chemotherapy treatment. This was accompanied by decreased activity in posterior brain regions after chemotherapy, particularly those involved in visual processing, for the breast cancer group compared to controls. These findings are discussed as evidence for a possible anterior shift in neural processing to compensate for deficiencies in posterior brain regions, consistent with an accelerated aging account. Cancer and chemotherapy can impact brain regions underlying episodic memory, leading to additional recruitment of control regions, which may be linked to mechanisms related to aging.

The Effects of Healthy Ageing on Cerebral Blood Flow Responses to Cognitive Testing

Background: Transcranial Doppler Ultrasonography (TCD) can be utilised to measure the tight coupling of cerebral blood flow velocity (CBFv) in response to cognitive demand by task activation, termed neurovascular coupling.

Aims: To investigate the differences in neurovascular coupling between healthy older (>50 years) and younger (18-49 years) adults in response to cognitive testing.

Methods: Fifty-four older (n=25) and younger (n=29) adults underwent continuous bilateral TCD, beat-to-beat blood pressure (MAP; Finapres), heart rate (HR; electrocardiogram), and end-tidal CO₂ (ETCO₂; capnography) monitoring. After a 5-min baseline period, memory (M1-4: recalling three learned words, learning a name and address, recalling US presidents and UK prime ministers, and recalling the previously learned name and address) and visuospatial (V1-4: drawing a cube and infinity diagram, drawing a clock face, counting dots, and recognising obscured letters) tasks from the Addenbrooke's Cognitive Examination (ACE-III) were performed. Data are mean (standard deviation).

Results: In the memory paradigms, the peak percentage change in CBFv differed significantly between younger and older groups only in the dominant hemisphere during the M1 task, (2.17 (9.16)% vs. 8.38 (9.27)%, respectively, p=0.017). In the visuospatial paradigm, there were also significant differences in peak percentage change in CBFv between younger and older groups in the V1 (5.87 (8.32)% vs. 11.89 (6.60)%, p=0.005) and V2 tasks (6.30 (8.72)% vs. 11.30 (7.77)%, p=0.032).

Conclusion: Healthy older adults demonstrate augmented cerebrovascular physiology in response to cognitive challenge compared to younger adults. The impact of abnormal ageing on cerebrovascular physiology, for example, related to cognitively impaired states, requires further investigation.

Longitudinal Changes in Whole-Brain Functional Connectivity Strength Patterns and the Relationship With the Global Cognitive Decline in Older Adults

Aging is associated with changes in brain functional patterns as well as cognition. The present research sought to investigate longitudinal changes in whole brain functional connectivity strength (FCS) and cognitive performance scores in very old cognitively unimpaired individuals. We studied 34 cognitively normal elderly individuals at both baseline and 4-year follow-up (baseline age = 78 ± 3.14 years) with resting-state functional magnetic resonance imaging (r-fMRI), structural MRI scans, and neuropsychological assessments conducted. Voxel-based whole brain FCS was calculated and we found that bilateral superior parietal and medial frontal regions showed decreased FCS, while the supplementary motor area (SMA) and insula showed increased FCS with age, along with a decrease in bilateral prefrontal cortical thickness. The changes of FCS in left precuneus were associated with an aging-related decline in global cognition. Taken together, our results suggest changes in FCS with aging with the precuneus as a hub and this may underlie changes in global cognition that accompany aging. These findings help better understand the normal aging mechanism.