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Systemic racism can have broad impacts on health in ethnoracial minorities. One way is by suppressing socioeconomic status (SES) levels through barriers to achieve higher income, wealth, and educational attainment. Additionally, the weathering hypothesis proposes that the various stressful adversities faced by ethnoracial minorities lead to greater wear and tear on the body, known as allostatic load. In the present study, we extend these ideas to cognitive health in a tri-ethnic sample of young adults—when cognition and brain health is arguably at their peak. Specifically, we tested competing mediation models that might shed light on how two key factors caused by systemic racism—SES and perceived stress—intersect to explain ethnoracial disparities in cognition. We found evidence for partial mediation via a pathway from SES to stress on episodic memory, working memory capacity, and executive function in Black Americans relative to non-Hispanic White Americans. Additionally, we found that stress partially mediated the ethnoracial disparities in working memory updating for lower SES Black and Hispanic Americans relative to non-Hispanic White Americans, showing that higher SES can sometimes reduce the negative effects stress has on these disparities in some cognitive domains. Overall, these findings suggest that multiple pathways exist in which lower SES creates a stressful environment to impact ethnoracial disparities cognition. These pathways differ depending on the specific ethnoracial category and cognitive domain. The present results may offer insight into strategies to help mitigate the late-life risk for neurocognitive disorders in ethnoracial minorities. [ABSTRACT FROM AUTHOR]

Fractal dimensionality (FD) measures the complexity within the folds and ridges of cortical and subcortical structures. We tested the degree that FD might provide a new perspective on the atrophy-compensation hypothesis: age or disease-related atrophy causes a compensatory neural response in the form of increased brain activity in the prefrontal cortex to maintain cognition. Brain structural and functional data were collected from 63 middle-aged and older adults and 18 young-adult controls. Two distinct patterns of FD were found that separated cortical from subcortical structures. Subcortical FD was more strongly negatively correlated with age than cortical FD, and cortical FD was negatively associated with brain activity during memory retrieval in medial and lateral parietal cortices uniquely in middle-aged and older adults. Multivariate analyses revealed that the lower FD/higher brain activity pattern was associated with poorer cognition—patterns not present in young adults, consistent with compensation. Bayesian analyses provide further evidence against the modal interpretation of the atrophy-compensation hypothesis in the prefrontal cortex—a key principle found in some neurocognitive theories of aging. • Fractal dimensionality (FD) was measured in cortical and subcortical structures. • We provided a novel test of the atrophy-compensation hypothesis. • Cortical FD was negatively associated with brain activity during memory retrieval. • Lower FD and greater brain activity were associated with poorer cognition. • Findings argue against the modal perspective of the atrophy-compensation hypothesis. [ABSTRACT FROM AUTHOR]

Longitudinal research suggests that genetic, lifestyle, and environmental factors enhance one's risk for developing Alzheimer's disease and related dementias (ADRD). However, it is not known how an accumulation of such factors impact brain functioning. One barrier to this research is that increased risk for ADRD affects the cerebrovascular system and, therefore, alters the link between neural activity and the fMRI BOLD signal. To better interpret fMRI findings, several steps were taken to adjust fMRI activity thereby reducing such cerebrovascular effects. We hypothesized that as the number of ADRD risk factors increase, brain regions within the medial temporal lobes and the default mode network would exhibit altered brain activity during an episodic memory retrieval task. Middle-aged and older adults (aged 50-74) free of dementia were recruited with varying levels of risk and underwent a neuropsychological battery and fMRI. In the memory task, participants viewed a pair of pictures. In an alternative-forced-choice test, participants viewed a picture cue and had to determine which of four pictures was paired with the cue. Increased dementia risk was positively associated with brain activity in regions of interest within the default mode network, the hippocampus, and the entorhinal cortex during memory retrieval. Whole-brain analyses revealed additional positive associations in prefrontal and occipito-temporal cortices. Risk factors most contributing to these elevated levels of brain activity included hypertension, diabetes, obesity, and cholesterol. We also ruled out confounds due to in-scanner performance and premorbid ability. Cumulative risk might represent early signs of burnout in brain regions underlying episodic memory. [ABSTRACT FROM AUTHOR]

Experiences of discrimination have been associated with poorer episodic memory in Black Americans. However, resilience resources at multiple levels (individual, social, and endowed) may act as a buffer to protect future memory decline, especially in the face of discrimination. Using longitudinal data from the 2006–2016 Health and Retirement Study (N = 1862), we tested whether Black Americans aged 50 and older would show different trajectories of episodic memory depending on their reported experiences of discrimination (everyday and major lifetime) and resilience resources. Analyses were conducted in three steps: (1) joint latent cluster mixed modeling (JLCMM) to estimate the number of classes, (2) barycentric discriminant analyses (BADA) to model the combined influence of discrimination and resilience resources between each memory class, and (3) multinomial regression analyses to explore interactions between discrimination and resilience resources. JLCMM resulted in three memory classes that differentiated baseline from longitudinal memory performance: "High Decliners," "Low Decliners," and "Low Stable." Two independent patterns described the relationships between the three classes in the context of discrimination and resilience resources. First, compared with High Decliners, the two lower baseline memory classes (Low Decliners and Low Stable) reported more everyday discrimination and lower individual and endowed resilience resources. Second, although the Low Stable class did not report different levels of discrimination, they had more social resilience resources (greater social support and more social contact) than both declining classes. Black Americans in later life have heterogeneous patterns of memory trajectories as demonstrated by the three memory classes identified. Those with lower baseline memory experienced more everyday discrimination and had fewer resilience resources compared to those with high baseline performance (High Decliners). Greater social resilience resources were associated with maintained episodic memory over time in Black Americans. • Memory trajectories up to 10 years were investigated among older Black Americans. • Three memory profiles differentiated baseline and longitudinal performance. • Lower baseline groups had more discrimination and fewer resilience resources. • Lower baseline groups had the poorest physical and cognitive health outcomes. • The stable longitudinal group had greater social resilience resources. [ABSTRACT FROM AUTHOR]

Sustained engagement in mentally challenging activities has been shown to improve memory in older adults. We hypothesized that a busy schedule would be a proxy for an engaged lifestyle and would facilitate cognition. Here, we examined the relationship between busyness and cognition in adults aged 50-89. Participants (N = 330) from the Dallas Lifespan Brain Study (DLBS) completed a cognitive battery and the Martin and Park Environmental Demands Questionnaire (MPED), an assessment of busyness. Results revealed that greater busyness was associated with better processing speed, working memory, episodic memory, reasoning, and crystallized knowledge. Hierarchical regressions also showed that, after controlling for age and education, busyness accounted for significant additional variance in all cognitive constructs-especially episodic memory. Finally, an interaction between age and busyness was not present while predicting cognitive performance, suggesting that busyness was similarly beneficial in adults aged 50-89. Although correlational, these data demonstrate that living a busy lifestyle is associated with better cognition. [ABSTRACT FROM AUTHOR]

• Used fMRI to identify brain activity due to the activation of aging stereotypes. • Stereotypes increased activity in parietal midline regions. • This activity was associated with reduced errors. • Results are consistent with the regulatory fit hypothesis. We report the first neuroimaging experiment to investigate the impact of explicitly activating aging stereotypes (i.e., stereotype threat) on brain activity during cognitive tasks. Cognitively normal older adults read about aging stereotypes or a control passage prior to taking episodic memory, working memory, and a non-demanding control task during fMRI. At the group level, stereotype activation did not impact cognitive performance or measures sensitive to stress and anxiety (physiological or self-report), but like prior work, highly educated and retired adults exhibited greater stereotype effects on episodic memory. At the neural level, stereotype activation did not impact brain activity in executive control or emotional regulation regions previously linked to stereotype threat effects in younger adults, suggesting that stereotype threat operates differently in older adults. Instead, on each task, the stereotype group showed more brain activity than the control group in parietal midline regions (e.g., precuneus, posterior cingulate). Although activity in these regions can arise from many processes, they have previously been associated with self-referential thinking and error-prevention focus, and in our study, brain activity in these regions was associated with slower responses and lower false alarm errors on the episodic memory task. Collectively, these findings are more consistent with the regulatory fit hypothesis than an executive control interference hypothesis of stereotype threat effects in older adults, whereby older adults adopt an error-prevention mindset in response to explicit stereotype threat. [ABSTRACT FROM AUTHOR]

Episodic memory decline is a hallmark of normal cognitive aging. Here, we report the first event-related fMRI study to directly investigate age differences in the neural reactivation of qualitatively rich perceptual details during recollection. Younger and older adults studied pictures of complex scenes at different presentation durations along with descriptive verbal labels, and these labels subsequently were used during fMRI scanning to cue picture recollections of varying perceptual detail. As expected from prior behavioral work, the two age groups subjectively rated their recollections as containing similar amounts of perceptual detail, despite objectively measured recollection impairment in older adults. In both age groups, comparisons of retrieval trials that varied in recollected detail revealed robust activity in brain regions previously linked to recollection, including hippocampus and both medial and lateral regions of the prefrontal and posterior parietal cortex. Critically, this analysis also revealed recollection-related activity in visual processing regions that were active in an independent picture-perception task, and these regions showed age-related reductions in activity during recollection that cannot be attributed to age differences in response criteria. These fMRI findings provide new evidence that aging reduces the absolute quantity of perceptual details that are reactivated from memory, and they help to explain why aging reduces the reliability of subjective memory judgments. [ABSTRACT FROM AUTHOR]

• Do separate risk factors for Alzheimer's disease (AD) affect similar brain regions? • We reviewed task-evoked fMRI studies of episodic memory in AD risk groups. • AD risks were associated with non-localized, widespread brain activity alterations. • The AD risk patterns were characterized by both greater and lower brain activity. • Mixed fMRI findings do not indicate clear use as diagnostic tool. Many risk factors have been identified that predict future progression to Alzheimer's disease (AD). However, clear links have yet to be made between these risk factors and how they affect brain functioning in early stages of AD. We conducted a narrative review and a quantitative analysis to better understand the relationship between nine categories of AD risk (i.e., brain pathology, genetics/family history, vascular health, head trauma, cognitive decline, engagement in daily life, late-life depression, sex/gender, and ethnoracial group) and task-evoked fMRI activity during episodic memory in cognitively-normal older adults. Our narrative review revealed widespread regional alterations of both greater and lower brain activity with AD risk. Nevertheless, our quantitative analysis revealed that a subset of studies converged on two patterns: AD risk was associated with (1) greater brain activity in frontal and parietal regions, but (2) reduced brain activity in hippocampal and occipital regions. The brain regions affected depended on the assessed memory stage (encoding or retrieval). Although the results clearly indicate that AD risks impact brain activity, we caution against using fMRI as a diagnostic tool for AD at the current time because the above consistencies were present among much variability, even among the same risk factor. [ABSTRACT FROM AUTHOR]

Memory consolidation is well known to occur during sleep, but might start immediately after encoding new information while awake. While consolidation processes are important across the lifespan, they may be even more important to maintain memory functioning in old age. We tested whether a novel measure of information processing known as network complexity might be sensitive to post-encoding consolidation mechanisms in a sample of young, middle-aged, and older adults. Network complexity was calculated by assessing the irregularity of brain signals within a network over time using multiscale entropy. To capture post-encoding mechanisms, network complexity was estimated using functional magnetic resonance imaging (fMRI) during rest before and after encoding of picture pairs, and subtracted between the two rest periods. Participants received a five-alternative-choice memory test to assess associative memory performance. Results indicated that aging was associated with an increase in network complexity from pre- to post-encoding in the default mode network (DMN). Increases in network complexity in the DMN also were associated with better subsequent memory across all age groups. These findings suggest that network complexity is sensitive to post-encoding consolidation mechanisms that enhance memory performance. These post-encoding mechanisms may represent a pathway to support memory performance in the face of overall memory declines. [ABSTRACT FROM AUTHOR]