Age differences in prefontal recruitment during verbal working memory maintenance depend on memory load

Registered report: Age-preserved semantic memory and the CRUNCH effect manifested as differential semantic control networks: An fMRI study

Semantic memory representations are generally well maintained in aging, whereas semantic control is thought to be more affected. To explain this phenomenon, this study tested the predictions of the Compensation-Related Utilization of Neural Circuits Hypothesis (CRUNCH), focusing on task demands in aging as a possible framework. The CRUNCH effect would manifest itself in semantic tasks through a compensatory increase in neural activation in semantic control network regions but only up to a certain threshold of task demands. This study compares 39 younger (20-35 years old) with 39 older participants (60-75 years old) in a triad-based semantic judgment task performed in an fMRI scanner while manipulating task demand levels (low versus high) through semantic distance. In line with the CRUNCH predictions, differences in neurofunctional activation and behavioral performance (accuracy and response times) were expected in younger versus older participants in the low- versus high-demand conditions, which should be manifested in semantic control Regions of Interest (ROIs). Our older participants had intact behavioral performance, as proposed in the literature for semantic memory tasks (maintained accuracy and slower response times (RTs)). Age-invariant behavioral performance in the older group compared to the younger one is necessary to test the CRUNCH predictions. The older adults were also characterized by high cognitive reserve, as our neuropsychological tests showed. Our behavioral results confirmed that our task successfully manipulated task demands: error rates, RTs and perceived difficulty increased with increasing task demands in both age groups. We did not find an interaction between age group and task demand, or a statistically significant difference in activation between the low- and high-demand conditions for either RTs or accuracy. As for brain activation, we did not find the expected age group by task demand interaction, or a significant main effect of task demand. Overall, our results are compatible with some neural activation in the semantic network and the semantic control network, largely in frontotemporoparietal regions. ROI analyses demonstrated significant effects (but no interactions) of task demand in the left and right inferior frontal gyrus, the left posterior middle temporal gyrus, the posterior inferior temporal gyrus and the prefrontal gyrus. Overall, our test did not confirm the CRUNCH predictions.

Sensitivity to and Control of Distraction: Distractor-Entrained Oscillation and Frontoparietal EEG Gamma Synchronization

While recent advancements have been made towards a better understanding of the involvement of the prefrontal cortex (PFC) in the context of cognitive control, the exact mechanism is still not fully understood. Successful behavior requires the correct detection of goal-relevant cues and resisting irrelevant distractions. Frontal parietal networks have been implicated as important for maintaining cognitive control in the face of distraction. The present study investigated the role of gamma-band power in distraction resistance and frontoparietal networks, as its increase is linked to cholinergic activity. We examined changes in gamma activity and their relationship to frontoparietal top-down modulation for distractor challenges and to bottom-up distractor processing. Healthy young adults were tested using a modified version of the distractor condition sustained attention task (dSAT) while wearing an EEG. The modified distractor was designed so that oscillatory activities could be entrained to it, and the strength of entrainment was used to assess the degree of distraction. Increased top-down control during the distractor challenge increased gamma power in the left parietal regions rather than the right prefrontal regions predicted from rodent studies. Specifically, left parietal gamma power increased in response to distraction where the amount of this increase was negatively correlated with the neural activity reflecting bottom-up distractor processing in the visual area. Variability in gamma power in right prefrontal regions was associated with increased response time variability during distraction. This may suggest that the right prefrontal region may contribute to the signaling needed for top-down control rather than its implementation.

Modulation of movement-related oscillatory signatures by cognitive interference in healthy aging

Age-related changes in the neurophysiology underlying motor control are well documented, but whether these changes are specific to motor function or more broadly reflect age-related alterations in fronto-parietal circuitry serving attention and other higher-level processes remains unknown. Herein, we collected high-density magnetoencephalography (MEG) in 72 healthy adults (age 28-63 years) as they completed an adapted version of the multi-source interference task that involved two subtypes of cognitive interference (i.e., flanker and Simon) and their integration (i.e., multi-source). All MEG data were examined for age-related changes in neural oscillatory activity using a whole-brain beamforming approach. Our primary findings indicated robust behavioral differences in task performance based on the type of interference, as well as stronger beta oscillations with increasing age in the right dorsolateral prefrontal cortices (flanker and multi-source conditions), left parietal (flanker and Simon), and medial parietal regions (multi-source). Overall, these data indicate that healthy aging is associated with alterations in higher-order association cortices that are critical for attention and motor control in the context of cognitive interference.

Prefrontal cortical activity during uneven terrain walking in younger and older adults

Introduction

Walking in complex environments increases the cognitive demand of locomotor control; however, our understanding of the neural mechanisms contributing to walking on uneven terrain is limited. We used a novel method for altering terrain unevenness on a treadmill to investigate the association between terrain unevenness and cortical activity in the prefrontal cortex, a region known to be involved in various cognitive functions.

Methods

Prefrontal cortical activity was measured with functional near infrared spectroscopy while participants walked on a novel custom-made terrain treadmill surface across four different terrains: flat, low, medium, and high levels of unevenness. The assessments were conducted in younger adults, older adults with better mobility function and older adults with worse mobility function. Mobility function was assessed using the Short Physical Performance Battery. The primary hypothesis was that increasing the unevenness of the terrain would result in greater prefrontal cortical activation in all groups. Secondary hypotheses were that heightened prefrontal cortical activation would be observed in the older groups relative to the younger group, and that prefrontal cortical activation would plateau at higher levels of terrain unevenness for the older adults with worse mobility function, as predicted by the Compensation Related Utilization of Neural Circuits Hypothesis.

Results

The results revealed a significant main effect of terrain, indicating a significant increase in prefrontal cortical activation with increasing terrain unevenness during walking in all groups. A significant main effect of group revealed that prefrontal cortical activation was higher in older adults with better mobility function compared to younger adults and older adults with worse mobility function in all pooled terrains, but there was no significant difference in prefrontal cortical activation between older adults with worse mobility function and younger adults. Contrary to our hypothesis, the older group with better mobility function displayed a sustained increase in activation but the other groups did not, suggestive of neural compensation. Additional findings were that task-related increases in prefrontal cortical activation during walking were lateralized to the right hemisphere in older adults with better mobility function but were bilateral in older adults with worse mobility function and younger adults.

Discussion

These findings support that compared to walking on a flat surface, walking on uneven terrain surfaces increases demand on cognitive control resources as measured by prefrontal cortical activation.

Brain atrophy, reduced cerebral perfusion, arterial stiffening, and wall thickening with aging coincide with stimulus-specific changes in fMRI-BOLD responses

The aim of this study was to investigate how aging affects blood flow and structure of the brain. It was hypothesized older individuals would have lower gray matter volume (GMV), resting cerebral blood flow (CBF0), and depressed responses to isometabolic and neurometabolic stimuli. In addition, increased carotid-femoral pulse-wave velocity (PWV), carotid intima-media thickness (IMT), and decreased brachial flow-mediated dilation (FMD) would be associated with lower CBF0, cerebrovascular reactivity (CVR), and GMV. Brain scans (magnetic resonance imaging) and cardiovascular examinations were conducted in young (age = 24 ± 3 yr, range = 22-28 yr; n = 13) and old (age = 71 ± 4 yr; range = 67-82 yr, n = 14) participants, and CBF0, CVR [isometabolic % blood oxygen level-dependent (BOLD) in response to a breath hold (BH)], brain activation patterns during a working memory task (neurometabolic %BOLD response to N-back trial), GMV, PWV, IMT, and FMD were measured. CBF0 and to a lesser extent CVRBH were lower in the old group (P ≤ 0.050); however, the increase in the %BOLD response to the memory task was not blunted (P ≥ 0.2867). Age-related differential activation patterns during the working memory task were characterized by disinhibition of the default mode network in the old group (P < 0.0001). Linear regression analyses revealed PWV, and IMT were negatively correlated with CBF0, CVRBH, and GMV across age groups, but within the old group alone only the relationships between PWV-CVRBH and IMT-GMV remained significant (P ≤ 0.0183). These findings suggest the impacts of age on cerebral %BOLD responses are stimulus specific, brain aging involves alterations in cerebrovascular and possibly neurocognitive control, and arterial stiffening and wall thickening may serve a role in cerebrovascular aging.NEW & NOTEWORTHY Cerebral perfusion was lower in old versus young adults. %Blood oxygen level-dependent (BOLD) responses to an isometabolic stimulus and gray matter volume were decreased in old versus young adults and associated with arterial stiffening and wall thickening. The increased %BOLD response to a neurometabolic stimulus appeared unaffected by age; however, the old group displayed disinhibition of the default mode network during the stimulus. Thus, age-related alterations in cerebral %BOLD responses were stimulus specific and related to arterial remodeling.

Abnormal brain activities of cognitive processes in cerebral small vessel disease: A systematic review of task fMRI studies

Cerebral small vessel disease (CSVD) is characterized by widespread functional changes in the brain, as evident from abnormal brain activations during cognitive tasks. However, the existing findings in this area are not yet conclusive. We systematically reviewed 25 studies reporting task-related fMRI in five cognitive domains in CSVD, namely executive function, working memory, processing speed, motor, and affective processing. The findings highlighted: (1) CSVD affects cognitive processes in a domain-specific manner; (2) Compensatory and regulatory effects were observed simultaneously in CSVD, which may reflect the interplay between the negative impact of brain lesion and the positive impact of cognitive reserve. Combined with behavioral and functional findings in CSVD, we proposed an integrated model to illustrate the relationship between altered activations and behavioral performance in different stages of CSVD: functional brain changes may precede and be more sensitive than behavioral impairments in the early pre-symptomatic stage; Meanwhile, compensatory and regulatory mechanisms often occur in the early stages of the disease, while dysfunction/decompensation and dysregulation often occur in the late stages. Overall, abnormal hyper-/hypo-activations are crucial for understanding the mechanisms of small vessel lesion-induced behavioral dysfunction, identifying potential neuromarker and developing interventions to mitigate the impact of CSVD on cognitive function.

Performance during attention-demanding walking conditions in older adults

BACKGROUND

Conventional balance and gait assessments for fall risk screening are often conducted under unperturbed conditions. However, older adults can allocate their attention to motor tasks (balance or walking) without revealing performance deficiencies, posing a challenge in identifying those with compromised gait and balance.

RESEARCH QUESTIONS

Do community-dwelling older adults exhibit greater changes in cognitive and/or walking performance under balance-challenging conditions compared to typical dual-task walking conditions?

METHODS

Twenty-nine healthy, community-dwelling older adults performed four cognitive tasks (visual and auditory Stroop tasks, Clock task, and Paced Auditory Serial Addition Test) while walking with and without lateral treadmill sways (Perturbed vs. Unperturbed) and during standing. We calculated dual-task costs (DTC) and walking perturbation effects (WPE) as the percentage of change in cognitive and walking performance between dual and single-task conditions and between Perturbed and Unperturbed conditions, respectively.

RESULTS

Older adults exhibited similar DTC and WPE on cognitive task performance. However, in walking performance, they demonstrated significantly greater WPE than DTC across all gait and stability measures (p < 0.01), including the mean and variability of stride and margins of stability (MOS) measures, the variability of trunk movement and lower-limb joint angles, and the local stability measures. Older adults took shorter but wider steps, exhibited shorter MOSAP but greater MOSML, and experienced increased movement variability and walking instability to a greater extent than during dual-task walking. Overall, changes in variability and stability measures were more pronounced than those in mean gait measures.

SIGNIFICANCE

Introducing destabilizing perturbations to increase the task demands of balance and gait assessments is a more effective method to challenge older adults compared to simply adding a concurrent cognitive task. Fall screening assessments for community-dwelling older adults should incorporate balance-challenging conditions, such as introducing gait perturbations.

Impaired Neurovascular Coupling and Increased Functional Connectivity in the Frontal Cortex Predict Age-Related Cognitive Dysfunction

Impaired cerebrovascular function contributes to the genesis of age-related cognitive decline. In this study, the hypothesis is tested that impairments in neurovascular coupling (NVC) responses and brain network function predict cognitive dysfunction in older adults. Cerebromicrovascular and working memory function of healthy young (n = 21, 33.2±7.0 years) and aged (n = 30, 75.9±6.9 years) participants are assessed. To determine NVC responses and functional connectivity (FC) during a working memory (n-back) paradigm, oxy- and deoxyhemoglobin concentration changes from the frontal cortex using functional near-infrared spectroscopy are recorded. NVC responses are significantly impaired during the 2-back task in aged participants, while the frontal networks are characterized by higher local and global connection strength, and dynamic FC (p < 0.05). Both impaired NVC and increased FC correlate with age-related decline in accuracy during the 2-back task. These findings suggest that task-related brain states in older adults require stronger functional connections to compensate for the attenuated NVC responses associated with working memory load.

Toward precision brain health: accurate prediction of a cognitive index trajectory using neuroimaging metrics

The goal of precision brain health is to accurately predict individuals' longitudinal patterns of brain change. We trained a machine learning model to predict changes in a cognitive index of brain health from neurophysiologic metrics. A total of 48 participants (ages 21-65) completed a sensorimotor task during 2 functional magnetic resonance imaging sessions 6 mo apart. Hemodynamic response functions (HRFs) were parameterized using traditional (amplitude, dispersion, latency) and novel (curvature, canonicality) metrics, serving as inputs to a neural network model that predicted gain on indices of brain health (cognitive factor scores) for each participant. The optimal neural network model successfully predicted substantial gain on the cognitive index of brain health with 90% accuracy (determined by 5-fold cross-validation) from 3 HRF parameters: amplitude change, dispersion change, and similarity to a canonical HRF shape at baseline. For individuals with canonical baseline HRFs, substantial gain in the index is overwhelmingly predicted by decreases in HRF amplitude. For individuals with non-canonical baseline HRFs, substantial gain in the index is predicted by congruent changes in both HRF amplitude and dispersion. Our results illustrate that neuroimaging measures can track cognitive indices in healthy states, and that machine learning approaches using novel metrics take important steps toward precision brain health.

Trajectories and contributing factors of neural compensation in healthy and pathological aging

Neural degeneration is a hallmark of healthy aging and can be associated with specific cognitive impairments. However, neural degeneration per se is not matched by unremitting declines in cognitive abilities. Instead, middle-aged and older adults typically maintain surprisingly high levels of cognitive functioning, suggesting that the human brain can adapt to structural degeneration by neural compensation. Here, we summarize prevailing theories and recent empirical studies on neural compensation with a focus on often neglected contributing factors, such as lifestyle, metabolism and neural plasticity. We suggest that these factors moderate the relationship between structural integrity and neural compensation, maintaining psychological well-being and behavioral functioning. Finally, we discuss that a breakdown in neural compensation may pose a tipping point that distinguishes the trajectories of healthy vs pathological aging, but conjoint support from psychology and cognitive neuroscience for this alluring view is still scarce. Therefore, future experiments that target the concomitant processes of neural compensation and associated behavior will foster a comprehensive understanding of both healthy and pathological aging.

Age-related alterations in the oscillatory dynamics serving verbal working memory processing

Working memory (WM) is a foundational cognitive function involving the temporary storage of information. Unfortunately, WM is also one of the most sensitive cognitive functions to the detrimental effects of aging. Expanding the field's understanding of age-related WM changes is critical to advancing the development of strategies to mitigate age-related WM declines. In the current study, we investigated the neural mechanisms serving WM function in seventy-eight healthy aging adults (range: 20.2-65.2 years) using magnetoencephalography (MEG) and a Sternberg WM task with letter stimuli. Neural activity during the different phases of the WM task (i.e., encoding, maintenance, and retrieval) were imaged using a time-frequency resolved beamformer and whole-brain statistics were performed. We found stronger increases in theta activity and stronger decreases in alpha and beta activity (i.e., more negative relative to baseline) as a function of healthy aging. Specifically, age-related increases in theta activity were detected during the encoding period in the primary visual and left prefrontal cortices. Additionally, alpha and beta oscillations were stronger (i.e., more negative) during both encoding and maintenance in the left prefrontal cortex in older individuals. Finally, alpha and beta oscillations during the retrieval phase were stronger (i.e., more negative) in older participants within the prefrontal, parietal, and temporal cortices. Together, these results indicate that healthy aging strongly modulates the neural oscillatory dynamics serving WM function.

Menopause Status and Within-Group Differences in Chronological Age Affect the Functional Neural Correlates of Spatial Context Memory in Middle-Aged Females

Reductions in the ability to encode and retrieve past experiences in rich spatial contextual detail (episodic memory) are apparent by midlife-a time when most females experience spontaneous menopause. Yet, little is known about how menopause status affects episodic memory-related brain activity at encoding and retrieval in middle-aged premenopausal and postmenopausal females, and whether any observed group differences in brain activity and memory performance correlate with chronological age within group. We conducted an event-related task fMRI study of episodic memory for spatial context to address this knowledge gap. Multivariate behavioral partial least squares was used to investigate how chronological age and retrieval accuracy correlated with brain activity in 31 premenopausal females (age range, 39.55-53.30 years; mean age, 44.28 years; SD age, 3.12 years) and 41 postmenopausal females (age range, 46.70-65.14 years; mean age, 57.56 years; SD age, 3.93 years). We found that postmenopausal status, and advanced age within postmenopause, was associated with lower spatial context memory. The fMRI analysis showed that only in postmenopausal females, advanced age was correlated with decreased activity in occipitotemporal, parahippocampal, and inferior parietal cortices during encoding and retrieval, and poorer spatial context memory performance. In contrast, only premenopausal females exhibited an overlap in encoding and retrieval activity in angular gyrus, midline cortical regions, and prefrontal cortex, which correlated with better spatial context retrieval accuracy. These results highlight how menopause status and chronological age, nested within menopause group, affect episodic memory and its neural correlates at midlife.SIGNIFICANCE STATEMENT This is the first fMRI study to examine how premenopause and postmenopause status affect the neural correlates of episodic memory encoding and retrieval, and how chronological age contributes to any observed group similarities and differences. We found that both menopause status (endocrine age) and chronological age affect spatial context memory and its neural correlates. Menopause status directly affected the direction of age-related and performance-related correlations with brain activity in inferior parietal, parahippocampal, and occipitotemporal cortices across encoding and retrieval. Moreover, we found that only premenopausal females exhibited cortical reinstatement of encoding-related activity in midline cortical, prefrontal, and angular gyrus, at retrieval. This suggests that spatial context memory abilities may rely on distinct brain systems at premenopause compared with postmenopause.

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.

Age differences in the neural correlates of recollection: transient versus sustained fMRI effects

Prior functional magnetic resonance imaging findings in young adults indicate that recollection-sensitive neural regions dissociate according to the time courses of their respective recollection effects. Here, we examined whether such dissociations are also evident in older adults. Young and older participants encoded a series of word-image pairs, judging which of the denoted objects was the smaller. At the test, participants judged whether each of a series of test words was old or new. If a word was old, the requirement was to recall the associated image and maintain it over a variable delay period. Older adults demonstrated significantly lower associative memory performance than young adults. Transient recollection effects were identified in the left hippocampus, medial prefrontal cortex, and posterior cingulate, while sustained effects were widespread across left lateral cortex and were also evident in the bilateral striatum. Except for those in the left insula, all effects were age-invariant. These findings suggest that both transient and sustained recollection effects are largely stable across much of the healthy adult life span.

Cognitive intra-individual variability in breast cancer survivors: A systematic review

Subjective and objective cognitive impairments in Breast Cancer Survivors (BCS) often do not correlate. One important contribution to the reported disparities may be the reliance on mean-based cognitive performance. Cognitive intra-individual variability (IIV) may provide important insights into these reported disparities. Cognitive IIV refers to the fluctuation in performance for an individual on either one cognitive task across a trial or dispersed across tasks within a neuropsychological test battery. The purpose of this systematic review was to search for and examine the literature on cognitive IIV in BCS. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) approach was used to search for all articles related to cognitive IIV in BCS. MEDLINE (via PubMed), Embase, and Scopus databases were searched using detailed search terms and strategies. Initially, 164 articles were retrieved but only 4 articles met the criteria for this systematic review. BCS differed from healthy controls in similar ways across the four studies, generally demonstrating similar performance but showing increased cognitive IIV for the more difficult tasks. Differences were enhanced later during chemotherapy. The four studies provide support for cognitive IIV as a useful measure to detect the subtle objective cognitive change often reported by BCS but frequently not detected by standard normed-based cognitive testing. Unexpectedly, measures of cognitive IIV were not consistently associated with self-reported measures of cognition.

Does muscle strength predict working memory? A cross-sectional fNIRS study in older adults

Objective

Previous research has primarily focused on the association between muscle strength and global cognitive function in older adults, while the connection between muscle strength and advanced cognitive function such as inhibition and working memory (WM) remains unclear. This study aimed to investigate the relationship among muscle strength, WM, and task-related cortex hemodynamics.

Methods

We recruited eighty-one older adults. Muscle strength was measured using a grip and lower limb strength protocol. We measured the WM performance by using reaction time (RT) and accuracy (ACC) in the N-back task and the cortical hemodynamics of the prefrontal cortex (PFC) by functional near-infrared spectroscopy (fNIRS).

Results

We found positive correlations between grip strength (p < 0.05), 30-s sit-up (p < 0.05) and ACC, negative correlation between grip strength (p < 0.05) and RT. Furthermore, we observed positive correlations between grip strength and the level of oxygenated hemoglobin (HbO2) in dorsolateral prefrontal cortex, frontopolar area, ventrolateral prefrontal cortex (p < 0.05), and negative correlations between grip strength and the level of deoxygenated hemoglobin (Hb) in left dorsolateral prefrontal cortex, frontopolar area, left ventrolateral prefrontal cortex (p < 0.05). Additionally, we noticed positive correlations between RT and the level of Hb in left dorsolateral prefrontal cortex, right frontopolar area (p < 0.05), and negative correlations between RT and the level of HbO2 in left dorsolateral prefrontal cortex, frontopolar area (p < 0.05). However, the cortical hemodynamics did not mediate the relationship between muscle strength and WM performance (RT, ACC).

Conclusion

The grip strength of older adults predicted WM in the cross-section study. The level of hemodynamics in PFC can serve as a predictor of WM.

The iron-dopamine D1 coupling modulates neural signatures of working memory across adult lifespan

Brain iron overload and decreased integrity of the dopaminergic system have been independently reported as brain substrates of cognitive decline in aging. Dopamine (DA), and iron are co-localized in high concentrations in the striatum and prefrontal cortex (PFC), but follow opposing age-related trajectories across the lifespan. DA contributes to cellular iron homeostasis and the activation of D1-like DA receptors (D1DR) alleviates oxidative stress-induced inflammatory responses, suggesting a mutual interaction between these two fundamental components. Still, a direct in-vivo study testing the iron-D1DR relationship and their interactions on brain function and cognition across the lifespan is rare. Using PET and MRI data from the DyNAMiC study (n=180, age=20-79, %50 female), we showed that elevated iron content was related to lower D1DRs in DLPFC, but not in striatum, suggesting that dopamine-rich regions are less susceptible to elevated iron. Critically, older individuals with elevated iron and lower D1DR exhibited less frontoparietal activations during the most demanding task, which in turn was related to poorer working-memory performance. Together, our findings suggest that the combination of elevated iron load and reduced D1DR contribute to disturbed PFC-related circuits in older age, and thus may be targeted as two modifiable factors for future intervention.

Cross-hemispheric recruitment during action planning with increasing task demand

The recruitment of cross-hemispheric counterparts of lateralized prefrontal brain regions with increasing processing demand is thought to increase memory performance despite cognitive aging, but was recently reported to be present also in young adults working at their capacity limit. Here we ask if cross-hemispheric recruitment is a general strategy of the adult brain in that executive task demand would modulate bilateral activation beyond prefrontal cortex and across cognitive tasks. We analyzed data sets from two fMRI experiments investigating retrospective working memory maintenance and prospective action planning. We confirmed a cross-hemispheric recruitment of prefrontal cortex across tasks and experiments. Changes in lateralization due to planning further surfaced in the cerebellum, dorsal premotor and posterior parietal cortex. Parietal cortex thereby exhibited cross-hemispheric recruitment also during spatial but not verbal working memory maintenance. Our results confirm a domain-general role of prefrontal cortex in cross-hemispheric recruitment. They further suggest that other task-specific brain regions also recruit their idling cross-hemispheric counterparts to relocate executive processing power.

Maternal age differences in cognitive regulation: examination of associations and interactions between RSA and EEG frontoparietal alpha power coherence

Strong cognitive regulation is advantageous for flexible, responsive parenting. Optimal cognitive regulation is reliant on associations between physiological mechanisms of central and peripheral nervous system functioning. Across middle adulthood there may be shifts in how cognitive regulation functions, reflecting changes in the associations and interactions between these physiological mechanisms. Two physiological indicators of cognitive regulation are autonomic regulation of the heart (e.g., respiratory sinus arrhythmia, RSA) and activity of the brain's frontoparietal network (e.g., frontoparietal EEG alpha power coherence, FPc). In the current study we examined maternal age differences (N = 90, age M = 32.35 years, SD = 5.86 years) in correlations and interactions between RSA and FPc in the statistical prediction of cognitive regulation [i.e., executive function (EF), effortful control (EC), cognitive reappraisal (CR)]. Age-related patterns involving interaction between RSA and FPc were found, pointing to a potential shift from optimization to compensation for changes with aging or alternately, the effects of age-based decrements in functioning. Findings are discussed in the context of adult developmental changes in maternal caregiving.

Lifespan differences in visual short-term memory load-modulated functional connectivity

Working memory is critical to higher-order executive processes and declines throughout the adult lifespan. However, our understanding of the neural mechanisms underlying this decline is limited. Recent work suggests that functional connectivity between frontal control and posterior visual regions may be critical, but examinations of age differences therein have been limited to a small set of brain regions and extreme group designs (i.e., comparing young and older adults). In this study, we build on previous research by using a lifespan cohort and a whole-brain approach to investigate working memory load-modulated functional connectivity in relation to age and performance. The article reports on analysis of the Cambridge center for Ageing and Neuroscience (Cam-CAN) data. Participants from a population-based lifespan cohort (N = 101, age 23-86) performed a visual short-term memory task during functional magnetic resonance imaging. Visual short-term memory was measured with a delayed recall task for visual motion with three different loads. Whole-brain load-modulated functional connectivity was estimated using psychophysiological interactions in a hundred regions of interest, sorted into seven networks (Schaefer et al., 2018, Yeo et al., 2011). Results showed that load-modulated functional connectivity was strongest within the dorsal attention and visual networks during encoding and maintenance. With increasing age, load-modulated functional connectivity strength decreased throughout the cortex. Whole-brain analyses for the relation between connectivity and behavior were non-significant. Our results give additional support to the sensory recruitment model of working memory. We also demonstrate the widespread negative impact of age on the modulation of functional connectivity by working memory load. Older adults might already be close to ceiling in terms of their neural resources at the lowest load and therefore less able to further increase connectivity with increasing task demands.

The effects of age on neural correlates of recollection: transient versus sustained fMRI effects

Prior fMRI findings in young adults indicate that recollection-sensitive neural regions dissociate according to the time courses of their respective recollection effects. Here, we examined whether such dissociations are also evident in older adults. Young and older participants encoded a series of word-object image pairs, judging which of the denoted objects was the smaller. At test, participants first judged whether a test word was old or new. For items judged old, they were required to recall the associated image and hold it in mind across a variable delay period. A post-delay cue denoted which of three judgments should be made on the retrieved image. Older adults demonstrated significantly lower associative memory performance than young adults. Replicating prior findings, transient recollection effects were identified in the left hippocampus, medial prefrontal cortex and posterior cingulate, while sustained effects were widespread across left lateral cortex and were also evident in the bilateral striatum. With the exception of those in the left insula, all effects were age-invariant. These findings add to the evidence that recollection-related BOLD effects in different neural regions can be temporally dissociated. Additionally, the findings suggest that both transient and sustained recollection effects are largely stable across much of the healthy adult lifespan.

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.

Uneven terrain versus dual-task walking: differential challenges imposed on walking behavior in older adults are predicted by cognitive and sensorimotor function

Aging is associated with declines in walking function. To understand these mobility declines, many studies have obtained measurements while participants walk on flat surfaces in laboratory settings during concurrent cognitive task performance (dual-tasking). This may not adequately capture the real-world challenges of walking at home and around the community. Here, we hypothesized that uneven terrains in the walking path impose differential changes to walking speed compared to dual-task walking. We also hypothesized that changes in walking speed resulting from uneven terrains will be better predicted by sensorimotor function than cognitive function. Sixty-three community-dwelling older adults (65-93 yrs old) performed overground walking under varying walking conditions. Older adults were classified into two mobility function groups based on scores of the Short Physical Performance Battery. They performed uneven terrain walking across four surface conditions (Flat, Low, Medium, and High unevenness) and performed single and verbal dual-task walking on flat ground. Participants also underwent a battery of cognitive (cognitive flexibility, working memory, inhibition) and sensorimotor testing (grip strength, 2-pt discrimination, pressure pain threshold). Our results showed that walking speed decreased during both dual-task walking and across uneven terrain walking conditions compared to walking on flat terrain. Participants with lower mobility function had even greater decreases in uneven terrain walking speeds. The change in uneven terrain speed was associated with attention and inhibitory function. Changes in both dual-task and uneven terrain walking speeds were associated with 2-point tactile discrimination. This study further documents associations between mobility, executive functions, and somatosensation, highlights the differential costs to walking imposed by uneven terrains, and identifies that older adults with lower mobility function are more likely to experience these changes to walking function.

Alpha and Low Gamma Embedded With White Noise Binaural Beats Modulating Working Memory among Malaysian Young Adult: A Preliminary fMRI Study

Introduction: Binaural beats (BB) provisions alpha and gamma have been suggested to modulate working memory (WM), while white noise (WN) acted as a control condition. Methods: The current study overlays WN on alpha and gamma tones to study its modulating role on WM performance. A block-design n-back task paradigm used to determine the effect of load on embedded BB on WM performance using functional magnetic resonance imaging. Results: Six young adults (3 males and 3 females) with mean age of 23.5 ± 0.84 within the Kota Bharu vicinity participated in the study. A repeated-measures ANOVA (p<0.05) on response accuracy indicate medium effect size on condition (η2 =0.420), and large effect sizes on groups (η2 = 0.388) and load (η2 = 0.487). The potential practical difference is more evident on low- (0-back) and high-load (3-back). GWN provision marginally excels, implying its entrainment may benefit WM processing. A repeated-measures ANOVA (p<0.05) on reaction time (RT) implied a large effect size on all variables (condition: η2=0.065, groups: η2=0.227 and load: η2=0.169). It was observed that BB exposure elicits a slow processing speed which worsens RT. The neural correlates suggest activated regions in GWN and AWN are associated with attentional mechanisms and WM processes. Conclusion: Preliminary findings indicate both embedded BB has a potential to improve WM performance with the cost of slower processing speed. GWN provision modulates attentional mechanisms benefiting WM performance and AWN may enhance performance in extreme ends of WM load.

Working memory dysfunction in fibromyalgia is associated with genotypes of the catechol- O-methyltransferase gene: an event-related potential study

Recent findings have associated different COMT genotypes with working memory capacity in patients with fibromyalgia. Although it is thought that the COMT gene may influence neural correlates (P2 and P3 ERP components) underlying working memory impairment in this chronic-pain syndrome, it has not yet been explored. Therefore, the aim of the present research was to investigate the potential effect of the COMT gene in fibromyalgia patients on ERP working memory indices (P2 and P3 components). For this purpose, 102 participants (51 patients and 51 healthy control participants) took part in the experiment. Event-related potentials and behavioral responses were recorded while participants performed a spatial n-back task. Participants had to decide if the stimulus coincided or not in the same location as the one presented one (1-back condition) or two (2-back condition) trials before. Genotypes of the COMT gene were determined through a saliva sample from all participants. Present results significantly showed lower working memory performance (p < 0.05) in patients with fibromyalgia as compared to control participants (higher rate of errors and slower reaction times). At neural level, we found that patients exhibited enhanced frontocentral and parieto-occipital P2 amplitudes compared to control participants (p < 0.05). Interestingly, we also observed that only fibromyalgia patients carrying the Val/Val genotype of the COMT gene showed higher frontocentral P2 amplitudes than control participants (p < 0.05). Current results (behavioral outcomes and P2 amplitudes) confirmed the presence of an alteration in working memory functioning in fibromyalgia. The enhancement of frontocentral P2 could be reflecting that these patients would manifest an inefficient way of activating executive attention processes, in carriers of the Val/Val genotype of COMT. To our knowledge, the present findings are the first linking neural indices of working memory dysfunctions and COMT genotypes in fibromyalgia. Applying a subgroup of patient's strategy based on this genetic marker could be useful to establish more tailored therapeutical approaches.

Impact of experience on the sensitivity, acceptability, and intrusive of two subjective mental workload techniques: The NASA TLX and workload profile

BACKGROUND

Today's work environments have high cognitive demands, and mental workload is one of the main causes of work stress, human errors, and accidents. While several mental workload studies have compared the mental workload perceived by groups of experienced participants to that perceived by novice groups, no comparisons have been made between the same individuals performing the same tasks at different times.

OBJECTIVE

This work aims to compare NASA Task Load Index (NASA-TLX) to Workload Profile (WP) in terms of their sensitivity. The comparison considers the impact of experience and task differentiation in the same individual once a degree of experience has been developed in the execution of the same tasks. It also considers the acceptability and intrusivity of the techniques.

METHODS

The sample consisted of 30 participants who performed four tasks in two sessions. The first session was performed when participants had no experience; the second session was performed after a time of practice. Mental workload was assessed after each session. Statistical methods were used to compare the results.

RESULTS

The NASA-TLX proved to be more sensitive to experience, while the WP showed greater sensitivity to task differentiation. In addition, while both techniques featured a similar degree of intrusivity, the NASA-TLX received greater acceptability.

CONCLUSION

The acceptability of WP is low due to the high complexity of its dimensions and clarifying explanations of these may be necessary to increase acceptability. Future research proposals should be expanded to consider mental workload when designing work environments in current manufacturing environments.

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.

Longitudinal stability in working memory and frontal activity in relation to general brain maintenance

Cognitive functions are well-preserved for some older individuals, but the underlying brain mechanisms remain disputed. Here, 5-year longitudinal 3-back in-scanner and offline data classified individuals in a healthy older sample (baseline age = 64-68 years) into having stable or declining working-memory (WM). Consistent with a vital role of the prefrontal cortex (PFC), WM stability or decline was related to maintained or reduced longitudinal PFC functional responses. Subsequent analyses of imaging markers of general brain maintenance revealed higher levels in the stable WM group on measures of neurotransmission and vascular health. Also, categorical and continuous analyses showed that rate of WM decline was related to global (ventricles) and local (hippocampus) measures of neuronal integrity. Thus, our findings support a role of the PFC as well as general brain maintenance in explaining heterogeneity in longitudinal WM trajectories in aging.

Relationship of prefrontal brain lateralization to optimal cognitive function differs with age

There is considerable debate about whether additional fMRI-measured activity in the right prefrontal cortex readily observed in older adults represents compensatory activation that enhances cognition or whether maintenance of youthful brain activity best supports cognitive function in late adulthood. To investigate this issue, we tested a large lifespan sample of 461 adults (aged 20-89) and treated degree of left-lateralization in ventrolateral and dorsolateral prefrontal cortex during a semantic judgment fMRI task as an individual differences variable to predict cognition. We found that younger adults were highly left-lateralized, but lateralization did not predict better cognition, whereas higher left-lateralization of prefrontal cortex predicted better cognitive performance in middle-aged adults, providing evidence that left-lateralized, youth-like patterns are optimal in middle age. This relationship was reversed in older adults, with lower laterality scores associated with better cognition. The findings suggest that bilaterality in older adults facilitates cognition, but early manifestation of this pattern during middle age is characteristic of low performers. Implications of these findings for current theories of neurocognitive aging are discussed.

Involvement of executive control in neural capacity related to working memory in aging: an ERP P300 study

Executive control could be involved in neural capacity, which corresponds to the modulation of neural activity with increased task difficulty. Thus, by exploring the P300-an electrophysiological correlate of working memory-we examined the role played by executive control in both the age-related decline in working memory and neural capacity in aging. Event-related potentials (ERPs) were recorded while younger and older participants performed a Sternberg task with two set sizes (2 vs. 6 items), allowing us to calculate a neural capacity index. Participants also completed two control tasks (Stroop and 3-back tests), which were used to calculate a composite executive control index. Results indicated that working memory performance decreased with aging and difficulty. At the neural level, results indicated that the P300 amplitude varied with aging and also with task difficulty. In the low difficulty condition, frontal P300 amplitude was higher for older than for younger adults, whereas in the high difficulty condition, the amplitude of frontal and parietal P300 did not differ between both age groups. Results also suggest that task difficulty led to a decrease in parietal amplitude in both age groups and to an increase in frontal amplitude in younger but not older adults. Both executive control and frontal neural capacity mediated the age-related variance in working memory for older adults. Moreover, executive control mediated the age-related variance in the frontal neural capacity of older adults. Thus, the present study suggests a model for older adults in which executive control deficits with advancing age lead to less efficient frontal recruitment to cope with task difficulty (neural capacity), which in turn has a negative impact on working memory functioning.

Cognitive Intra-individual Variability in HIV: an Integrative Review

Nearly 30-50% of people living with HIV experience HIV-Associated Neurocognitive Disorder (HAND). HAND indicates performance at least one standard deviation below the normative mean on any two cognitive domains. This method for diagnosing or classifying cognitive impairment has utility, however, cognitive intraindividual variability provides a different way to understand cognitive impairment. Cognitive intraindividual variability refers to the scatter in cognitive performance within repeated measures of the same cognitive test (i.e., inconsistency) or across different cognitive tests (i.e., dispersion). Cognitive intraindividual variability is associated with cognitive impairment and cognitive decline in various clinical populations. This integrative review of 13 articles examined two types of cognitive intraindividual variability in people living with HIV, inconsistency and dispersion. Cognitive intraindividual variability appears to be a promising approach to detect subtle cognitive impairments that are not captured by traditional mean-based neuropsychological testing. Greater intraindividual variability in people living with HIV has been associated with: 1) poorer cognitive performance and cognitive decline, 2) cortical atrophy, both gray and white matter volume, 3) poorer everyday functioning (i.e., driving simulation performance), specifically medication adherence, and 4) even mortality. This inspires future directions for research. First, greater cognitive intraindividual variability may reflect a greater task demand on executive control to harness and regulate cognitive control over time. By improving executive functioning through cognitive training, it may reduce cognitive intraindividual variability which could slow down cognitive decline. Second, cognitive intraindividual variability may be reconsidered in prior cognitive intervention studies in which only mean-based cognitive outcomes were used. It is possible that such cognitive interventions may actually improve cognitive intraindividual variability, which could have clinical relevance.

Age-Related Learning and Working Memory Impairment in the Common Marmoset

Aging is the greatest risk factor for the development of neurodegenerative diseases, yet we still do not understand how the aging process leads to pathologic vulnerability. The research community has relied heavily on mouse models, but the considerable anatomic, physiological, and cognitive differences between mice and humans limit their translational relevance. Ultimately, these barriers necessitate the development of novel aging models. As a nonhuman primate (NHP), the common marmoset (Callithrix jacchus) shares many features in common with humans and yet has a significantly shorter lifespan (10 years) than other primates, making it ideally suited to longitudinal studies of aging. Our objective was to evaluate the marmoset as a model of age-related cognitive impairment. To do this, we used the Delayed Recognition Span Task (DRST) to characterize age-related changes in working memory capacity in a cohort of sixteen marmosets, of both sexes, varying in age from young adult to geriatric. These monkeys performed thousands of trials over periods of time ranging up to 50% of their adult lifespan. To our knowledge, this represents the most thorough cognitive profiling of any marmoset aging study conducted to date. By analyzing individual learning curves, we found that aged animals exhibited delayed onset of learning, slowed learning rate after onset, and decreased asymptotic working memory performance. These findings are not accounted for by age-related impairments in motor speed and motivation. This work firmly establishes the marmoset as a model of age-related cognitive impairment.SIGNIFICANCE STATEMENT Understanding the normal aging process is fundamental to identifying therapeutics for neurodegenerative diseases for which aging is the biggest risk factor. Historically, the aging field has relied on animal models that differ markedly from humans, constraining translatability. Here, we firmly establish a short-lived nonhuman primate (NHP), the common marmoset, as a key model of age-related cognitive impairment. We demonstrate, through continuous testing over a substantial portion of the adult marmoset lifespan, that aging is associated with both impaired learning and working memory capacity, unaccounted for by age-related changes in motor speed and motivation. Characterizing individual cognitive aging trajectories reveals inherent heterogeneity, which could lead to earlier identification of the onset of impairment, and extended timelines during which therapeutics are effective.

Dissociable neural mechanisms of cognition and well-being in youth versus healthy aging

Mental health, cognition, and their underlying neural processes in healthy aging are rarely studied simultaneously. Here, in a sample of healthy younger (n = 62) and older (n = 54) adults, we compared subjective mental health as well as objective global cognition across several core cognitive domains with simultaneous electroencephalography (EEG). We found significantly greater symptoms of anxiety, depression, and loneliness in youth and in contrast, greater mental well-being in older adults. Yet, global performance across core cognitive domains was significantly worse in older adults. EEG-based source imaging of global cognitive task-evoked processing showed reduced suppression of activity in the anterior medial prefrontal default mode network (DMN) region in older adults relative to youth. Global cognitive performance efficiency was predicted by greater activity in the right dorsolateral prefrontal cortex in younger adults and in contrast, by greater activity in right inferior frontal cortex in older adults. Furthermore, greater mental well-being in older adults related to lesser global task-evoked activity in the posterior DMN. Overall, these results suggest dissociated neural mechanisms underlying global cognition and mental well-being in youth versus healthy aging. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Understanding cognitive control in aging: A brain network perspective

Cognitive control decline is a major manifestation of brain aging that severely impairs the goal-directed abilities of older adults. Magnetic resonance imaging evidence suggests that cognitive control during aging is associated with altered activation in a range of brain regions, including the frontal, parietal, and occipital lobes. However, focusing on specific regions, while ignoring the structural and functional connectivity between regions, may impede an integrated understanding of cognitive control decline in older adults. Here, we discuss the role of aging-related changes in functional segregation, integration, and antagonism among large-scale networks. We highlight that disrupted spontaneous network organization, impaired information co-processing, and enhanced endogenous interference promote cognitive control declines during aging. Additionally, in older adults, severe damage to structural network can weaken functional connectivity and subsequently trigger cognitive control decline, whereas a relatively intact structural network ensures the compensation of functional connectivity to mitigate cognitive control impairment. Thus, we propose that age-related changes in functional networks may be influenced by structural networks in cognitive control in aging (CCA). This review provided an integrative framework to understand the cognitive control decline in aging by viewing the brain as a multimodal networked system.

Load-Dependent Prefrontal Cortex Activation Assessed by Continuous-Wave Near-Infrared Spectroscopy during Two Executive Tasks with Three Cognitive Loads in Young Adults

The present study examined the evolution of the behavioral performance, subjectively perceived difficulty, and hemodynamic activity of the prefrontal cortex as a function of cognitive load during two different cognitive tasks tapping executive functions. Additionally, it investigated the relationships between these behavioral, subjective, and neuroimaging data. Nineteen right-handed young adults (18–22 years) were scanned using continuous-wave functional near-infrared spectroscopy during the performance of n-back and random number generation tasks in three cognitive load conditions. Four emitter and four receptor optodes were fixed bilaterally over the ventrolateral and dorsolateral prefrontal cortices to record the hemodynamic changes. A self-reported scale measured the perceived difficulty. The findings of this study showed that an increasing cognitive load deteriorated the behavioral performance and increased the perceived difficulty. The hemodynamic activity increased parametrically for the three cognitive loads of the random number generation task and in a two-back and three-back compared to a one-back condition. In addition, the hemodynamic activity was specifically greater in the ventrolateral prefrontal cortex than in the dorsolateral prefrontal cortex for both cognitive tasks (random number generation and n-back tasks). Finally, the results highlighted some links between cerebral oxygenation and the behavioral performance, but not the subjectively perceived difficulty. Our results suggest that cognitive load affects the executive performance and perceived difficulty and that fNIRS can be used to specify the prefrontal cortex’s implications for executive tasks involving inhibition and working memory updating.

Measuring memory is harder than you think: How to avoid problematic measurement practices in memory research

We argue that critical areas of memory research rely on problematic measurement practices and provide concrete suggestions to improve the situation. In particular, we highlight the prevalence of memory studies that use tasks (like the "old/new" task: "have you seen this item before? yes/no") where quantifying performance is deeply dependent on counterfactual reasoning that depends on the (unknowable) distribution of underlying memory signals. As a result of this difficulty, different literatures in memory research (e.g., visual working memory, eyewitness identification, picture memory, etc.) have settled on a variety of fundamentally different metrics to get performance measures from such tasks (e.g., A', corrected hit rate, percent correct, d', diagnosticity ratios, K values, etc.), even though these metrics make different, contradictory assumptions about the distribution of latent memory signals, and even though all of their assumptions are frequently incorrect. We suggest that in order for the psychology and neuroscience of memory to become a more cumulative, theory-driven science, more attention must be given to measurement issues. We make a concrete suggestion: The default memory task for those simply interested in performance should change from old/new ("did you see this item'?") to two-alternative forced-choice ("which of these two items did you see?"). In situations where old/new variants are preferred (e.g., eyewitness identification; theoretical investigations of the nature of memory signals), receiver operating characteristic (ROC) analysis should be performed rather than a binary old/new task.

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.

Distinct neural activation patterns of age in subcomponents of inhibitory control: A fMRI meta-analysis

Inhibitory control (IC) is a fundamental cognitive function showing age-related change across the healthy lifespan. Since different cognitive resources are needed in the two subcomponents of IC (cognitive inhibition and response inhibition), regions of the brain are differentially activated. In this study, we aimed to determine whether there is a distinct age-related activation pattern in these two subcomponents. A total of 278 fMRI articles were included in the current analysis. Multilevel kernel density analysis was used to provide data on brain activation under each subcomponent of IC. Contrast analyses were conducted to capture the distinct activated brain regions for the two subcomponents, whereas meta-regression analyses were performed to identify brain regions with distinct age-related activation patterns in the two subcomponents of IC. The results showed that the right inferior frontal gyrus and the bilateral insula were activated during the two IC subcomponents. Contrast analyses revealed stronger activation in the superior parietal lobule during cognitive inhibition, whereas stronger activation during response inhibition was observed primarily in the right inferior frontal gyrus, bilateral insula, and angular gyrus. Furthermore, regression analyses showed that activation of the left anterior cingulate cortex, left inferior frontal gyrus, bilateral insula, and left superior parietal lobule increased and decreased with age during cognitive inhibition and response inhibition, respectively. The results showed distinct activation patterns of aging for the two subcomponents of IC, which may be related to the differential cognitive resources recruited. These findings may help to enhance knowledge of age-related changes in the activation patterns of IC.

Don't forget the little brain: A framework for incorporating the cerebellum into the understanding of cognitive aging

With the rapidly growing population of older adults, an improved understanding of brain and cognitive aging is critical, given the impacts on health, independence, and quality of life. To this point, we have a well-developed literature on the cortical contributions to cognition in advanced age. However, while this work has been foundational for our understanding of brain and behavior in older adults, subcortical contributions, particularly those from the cerebellum, have not been integrated into these models and frameworks. Incorporating the cerebellum into models of cognitive aging is an important step for moving the field forward. There has also been recent interest in this structure in Alzheimer's dementia, indicating that such work may be beneficial to our understanding of neurodegenerative disease. Here, I provide an updated overview of the cerebellum in advanced age and propose that it serves as a critical source of scaffolding or reserve for cortical function. Age-related impacts on cerebellar function further impact cortical processing, perhaps resulting in many of the activation patterns commonly seen in aging.

Presupposition processing declines with age

The present study investigates the processing of presuppositions across the life span and extends the findings of the only available study on presupposition processing and typical aging by Domaneschi and Di Paola (J Pragmat 140:70-87, 2019). In an online and offline task, we investigate the impact of cognitive load during the processing and recovery of two presupposition triggers-definite descriptions and change-of-state verbs-comparing a group of younger adults with a group of older adults. The collected experimental data show that (1) presupposition recovery declines during normal aging, (2) presupposition recovery of change-of-state verbs is more cognitively demanding for older adults than the recovery of definite descriptions, and lastly (3) presupposition recovery for the change-of-state verb begin is more demanding than the change-of-state verb stop. As of today, few works have directly investigated presupposition processing across the life span. To the best of our knowledge, this is the first work revealing that cognitive load directly impacts the recovery of presuppositions across the life span, which in turn suggests an involvement of verbal working memory.

Altered linear coupling between stimulus-evoked blood flow and oxygen metabolism in the aging human brain

Neural-vascular coupling (NVC) is the process by which oxygen and nutrients are delivered to metabolically active neurons by blood vessels. Murine models of NVC disruption have revealed its critical role in healthy neural function. We hypothesized that, in humans, aging exerts detrimental effects upon the integrity of the neural-glial-vascular system that underlies NVC. To test this hypothesis, calibrated functional magnetic resonance imaging (cfMRI) was used to characterize age-related changes in cerebral blood flow (CBF) and oxygen metabolism during visual cortex stimulation. Thirty-three younger and 27 older participants underwent cfMRI scanning during both an attention-controlled visual stimulation task and a hypercapnia paradigm used to calibrate the blood-oxygen-level-dependent signal. Measurement of stimulus-evoked blood flow and oxygen metabolism permitted calculation of the NVC ratio to assess the integrity of neural-vascular communication. Consistent with our hypothesis, we observed monotonic NVC ratio increases with increasing visual stimulation frequency in younger adults but not in older adults. Age-related changes in stimulus-evoked cerebrovascular and neurometabolic signal could not fully explain this disruption; increases in stimulus-evoked neurometabolic activity elicited corresponding increases in stimulus-evoked CBF in younger but not in older adults. These results implicate age-related, demand-dependent failures of the neural-glial-vascular structures that comprise the NVC system.

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.

Reduced parietal activation in participants with mild cognitive impairments during visual-spatial processing measured with functional near-infrared spectroscopy

Functional Near Infrared Spectroscopy (fNIRS) may be a suitable, simple, and cost-effective brain imaging technique for detecting divergent neuronal patterns at an early stage of neurodegeneration. In course of Mild Cognitive Impairment (MCI) or Alzheimer's disease (AD), a deficit in visual-spatial processing, located in the parietal cortex, is a reliable risk factor. Earlier, we established the application of the clock-hand-angle-discrimination task (ADT) during fNIRS to identify neuronal correlates of the visual-spatial processing in a healthy elderly sample. In this analysis, we aimed to measure and find out differences in the hemodynamic response in MCI participants compared to matched healthy controls. As expected, MCI participants showed more errors over all conditions of pointer length and a higher reaction time in the long and middle pointer length condition. Moreover, results revealed a significant reduction of cortical activation in MCI patients. There was a generally increased activity in both the right as compared to the left hemisphere and the superior parietal brain region as compared to the inferior parietal brain region in both groups. In summary, fNIRS can be implemented in the measurement of visual-spatial processing in MCI patients and healthy elderly based on ADT. MCI participants had difficulties to cope with the ADT. Since neuronal hypoactivity occurs with concomitant behavioral deficits, an additional analysis was performed on a subgroup of MCI patients who performed as well as the control group in behavior. This subgroup analysis also showed a hypoactivation of the parietal cortex, without evidence of a compensatory activation. Therefore, we assume that MCI patients are characterized by a deficit in the parietal cortex. Overall, these findings confirm our hypothesis that hemodynamic deficits in visual-spatial processing, localized in the parietal cortex, are reliable and early diagnostic markers for cognitive decline in risk groups for the development of AD.

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.

Unraveling the Cognitive-Motor Interaction in Individuals With Amnestic Mild Cognitive Impairment

PURPOSE

This study aimed to determine whether increasing the contribution of executive functions worsens dual-task performance in individuals with amnestic mild cognitive impairment (aMCI).

METHODS

Fourteen individuals with aMCI (mean [SD]: 74 [4] years) and 19 control adults (71 [5] years) recalled a list of letters in the order of presentation (SPAN-O) or in alphabetic order (SPAN-A) while ascending or descending a 3-step staircase. Dual-task cost (DTC) represented the average decrement of motor and cognitive performances during dual tasks, with greater DTC indicating worse performance.

RESULTS

SPAN-A (P < 0.001) and stair descent (P = 0.023) increased the DTC in both groups compared with SPAN-O and stair ascent. Furthermore, individuals with aMCI had a greater DTC (93.4 [41.2]%) than the control group (48.3 [27.9]%) for SPAN-A (P < 0.001). Dual-task cost was also greater in descent (76.6 [42.1]%) than ascent (64.0 [34.5]%) in individuals with aMCI (P = 0.024) but not in the control group (P = 0.99). Significant negative partial correlations (β < -0.39; P < 0.05) were found between Montreal Cognitive Assessment score and DTC, while controlling for age and physical function.

DISCUSSION AND CONCLUSIONS

A greater DTC in individuals with aMCI when the cognitive task requires working memory (SPAN-A) or during complex locomotor task (descent) suggests that aMCI impedes the capacity to perform 2 tasks simultaneously when higher-order cognitive processes are challenged. Furthermore, a greater DTC in our dual-task situations appears to reflect cognitive decline, as assessed by the Montreal Cognitive Assessment score. Overall, this study indicates that increasing the contribution of executive functions worsens the cognitive-motor interaction in individuals with aMCI.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1 available at: http://links.lww.com/JNPT/A375).

Functional coupling between CA3 and laterobasal amygdala supports schema dependent memory formation

The medial temporal lobe drives semantic congruence dependent memory formation. However, the exact roles of hippocampal subfields and surrounding brain regions remain unclear. Here, we used an established paradigm and high-resolution functional magnetic resonance imaging of the medial temporal lobe together with cytoarchitectonic probability estimates in healthy humans. Behaviorally, robust congruence effects emerged in young and older adults, indicating that schema dependent learning is unimpaired during healthy aging. Within the medial temporal lobe, semantic congruence was associated with hemodynamic activity in the subiculum, CA1, CA3 and dentate gyrus, as well as the entorhinal cortex and laterobasal amygdala. Importantly, a subsequent memory analysis showed increased activity for later remembered vs. later forgotten congruent items specifically within CA3, and this subfield showed enhanced functional connectivity to the laterobasal amygdala. As such, our findings extend current models on schema dependent learning by pinpointing the functional properties of subregions within the medial temporal lobe.