Biology subjects

Chappel-Farley, M. G.

Publications and source records attributed to Chappel-Farley, M. G..

5 recordsLinked to original sources

bioRxiv2024

Engagement in moderate-intensity physical activity supports overnight emotional memory retention in older adults

ImportancePreserving the ability to vividly recall emotionally rich experiences contributes to quality of life in older adulthood. While prior work suggests that moderate-intensity physical activity (MPA) may bolster memory, it is unclear whether this extends to emotionally salient memories consolidated during sleep. ObjectiveTo investigate associations between engagement in physical activity (PA) and overnight emotional memory retention and examine whether theoretically replacing 30-minutes of lower-intensity activity with MPA is associated with better consolidation. Design, Setting, and ParticipantsA cross-sectional study of 40 community-dwelling older adults free of neurological and psychiatric disorders. Data were collected from May 2018 to July 2022 and analyzed from January to July 2024. ExposuresParticipants completed an overnight polysomnography (PSG) with emotional memory tested before and after sleep and a self-report questionnaire assessing habitual PA. Main Outcome(s) and Measures(s)Emotional memory performance was assessed via recognition memory or mnemonic discrimination performance. Overnight memory retention was calculated by subtracting immediate test from delayed test performance for both recognition memory and mnemonic discrimination, with more negative scores indicating lower memory retention. Frequency and duration of MPA, light-intensity PA, non-exertive activity, and sedentary behavior were calculated from the Community Health Activities Model Program for Seniors (CHAMPS) Activities Questionnaire for Older Adults. Isotemporal substitution modelling evaluated whether statistically reallocating time spent in sedentary and lower-intensity activity to MPA was associated with better overnight memory retention. ResultsData from 40 participants were analyzed ({square}age=72.3{+/-}5.8, 26 female). Better overnight emotional recognition memory retention was associated with the frequency ({beta}=0.663, SE=0.212, p=0.003) and duration ({beta}=0.214, SE=0.101, p=0.042) of MPA. No relationships were found with mnemonic discrimination or neutral recognition memory. Statistically modelling the replacement of 30 minutes of lower-intensity activity with MPA was associated with better overnight retention of emotional memories ({beta}=0.108, SE=0.048, p=0.030), but not neutral ({beta}=-0.029, SE=0.069, p=0.679). Conclusions and RelevanceMPA may enhance sleep-dependent consolidation of emotional memories in older adults. Modest increases in MPA may yield significant benefits for sleep-dependent emotional memory retention. These findings may guide interventions to preserve memory function and inform public health recommendations by demonstrating that substituting even short durations of low-intensity activity for MPA could produce significant cognitive gains relevant for maintaining quality of life in older adulthood.

neuroscience↗

bioRxiv2024

Sleep defined by arousal threshold reveals decreases in corticocortical functional correlations independently from the conventional sleep stages

Reports of sleep-specific brain activity patterns have been constrained by assessing brain function as it related to the conventional polysomnographic sleep stages. This limits the variety of sleep states and underlying activity patterns that one can discover. The current study used all-night functional MRI sleep data and defined sleep behaviorally with auditory arousal threshold (AAT) to characterize sleep depth better by searching for novel neural markers of sleep depth that are neuroanatomically localized and temporally unrelated to the conventional stages. Functional correlation values calculated in a four-min time window immediately before the determination of AAT were entered into a linear mixed effects model, allowing multiple arousals across the night per subject into the analysis, and compared to models with sleep stage to determine the unique relationships with AAT. These unique relationships were for thalamocerebellar correlations, the relationship between the right language network and the right "default-mode network dorsal medial prefrontal cortex subsystem," and the relationship between thalamus and ventral attention network. These novel neural markers of sleep depth would have remained undiscovered if the data were merely analyzed with the conventional sleep stages. Significance StatementThe original classification of sleep into distinct stages used behavioral characteristics. With the proliferation of new techniques, the first experiments might have been to perform correlations with arousal threshold. These experiments have never been performed, either with functional MRI or with any other modern technique. The amount of communication between brain regions as measured by all-night functional magnetic resonance imaging was correlated with arousal threshold. This revealed novel neural markers of sleep depth that would have remained undiscovered if the data were merely analyzed with the conventional stages. This expands our understanding of sleep and its functions beyond the constraints imposed by the conventional stages.

neuroscience↗

bioRxiv2024

Cerebrovascular pathology mediates associations between hypoxemia during rapid eye movement sleep and medial temporal lobe structure and function in older adults

Obstructive sleep apnea (OSA) is common in older adults and is associated with medial temporal lobe (MTL) degeneration and memory decline in aging and Alzheimers disease (AD). However, the underlying mechanisms linking OSA to MTL degeneration and impaired memory remains unclear. By combining magnetic resonance imaging (MRI) assessments of cerebrovascular pathology and MTL structure with clinical polysomnography and assessment of overnight emotional memory retention in older adults at risk for AD, cerebrovascular pathology in fronto-parietal brain regions was shown to statistically mediate the relationship between OSA-related hypoxemia, particularly during rapid eye movement (REM) sleep, and entorhinal cortical thickness. Reduced entorhinal cortical thickness was, in turn, associated with impaired overnight retention in mnemonic discrimination ability across emotional valences for high similarity lures. These findings identify cerebrovascular pathology as a contributing mechanism linking hypoxemia to MTL degeneration and impaired sleep-dependent memory in older adults.

neuroscience↗

bioRxiv2023

Medial temporal lobe functional network architecture supports sleep-related emotional memory processing in older adults

Memory consolidation occurs via reactivation of a hippocampal index during non-rapid eye movement slow-wave sleep (NREM SWS) which binds attributes of an experience existing within cortical modules. For memories containing emotional content, hippocampal-amygdala dynamics facilitate consolidation over a sleep bout. This study tested if modularity and centrality--graph theoretical measures that index the level of segregation/integration in a system and the relative import of its nodes--map onto central tenets of memory consolidation theory and sleep-related processing. Findings indicate that greater network integration is tied to overnight emotional memory retention via NREM SWS expression. Greater hippocampal and amygdala influence over network organization supports emotional memory retention, and hippocampal or amygdala control over information flow are differentially associated with distinct stages of memory processing. These centrality measures are also tied to the local expression and coupling of key sleep oscillations tied to sleep-dependent memory consolidation. These findings suggest that measures of intrinsic network connectivity may predict the capacity of brain functional networks to acquire, consolidate, and retrieve emotional memories.

neuroscience↗

bioRxiv2023

Pathological brain states in Alzheimer's disease

Dynamic and rapid reconfigurations of neural activation patterns, known as brain states, support cognition. Recent analytic advances applied to functional magnetic resonance imaging now enable the quantification of brain states, which offers a substantial methodological improvement in characterizing spatiotemporal dynamics of activation over previous functional connectivity methods. Dysfunction to the persistence and temporal transitions between discrete brain states may be proximal factors reflecting neurophysiological disruptions in Alzheimers disease, although this has not yet been established. Here, we identified six distinct brain states, representing spatiotemporal trajectories of coactivation at single time points, in older adults across the Alzheimers disease continuum. Critically, we identified a pathological brain state that reflects coactivation within limbic regions. Higher persistence within and transitions to this limbic state, at the expense of other brain states, is associated with an increased likelihood of a clinically impaired diagnosis, worse cognitive performance, greater Alzheimers pathology, and neurodegeneration. Together, our results provide compelling evidence that neural activity settling into a pathological limbic state reflects the progression to Alzheimers disease. As brain states have recently been shown to be modifiable targets, this work may inform the development of novel neuromodulation techniques to reduce limbic state persistence. This application would be an innovative clinical approach to rescue cognitive decline in the early stages of Alzheimers disease.

neuroscience↗