Introduction
Growing evidence suggests that impairment in rest‐activity rhythms may be a risk factor for cognitive decline and impairment in the aging population. However, previous studies included ...only a limited set of rest‐activity metrics and produced mixed findings. We studied a comprehensive set of parametric and nonparametric characteristics of rest‐activity rhythms in relation to mild cognitive impairment (MCI) and probable dementia in a cohort of older women.
Methods
The prospective analysis included 763 women enrolled in two ancillary studies of the Women's Health Initiative (WHI): the WHI Memory Study‐Epidemiology of Cognitive Health Outcomes and Objective Physical Activity and Cardiovascular Health studies. The association between accelerometry‐based rest‐activity parameters and centrally adjudicated MCI and probable dementia were determined using Cox regression models adjusted for sociodemographic characteristics, lifestyle factors, and comorbidities.
Results
Overall, the results support a prospective association between weakened rest‐activity rhythms (e.g., reduced amplitude and overall rhythmicity) and adverse cognitive outcomes. Specifically, reduced overall rhythmicity (pseudo F statistic), lower amplitude and activity level (amplitude/relative amplitude, mesor, and activity level during active periods of the day M10), and later activity timing (acrophase and midpoint of M10) were associated with a higher risk for MCI and probable dementia. Women with lower amplitude and mesor also exhibited faster cognitive decline over follow‐up.
Conclusion
Weakened rest‐activity rhythms may be predictive markers for cognitive decline, MCI, and dementia among older women.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Objective. Mild cognitive impairment (MCI) and dementia due to Alzheimer's disease (AD) have been shown to induce perturbations to normal neuronal behavior and disrupt neuronal networks. Recent work ...suggests that the dynamic properties of resting-state neuronal activity could be affected by MCI and AD-induced neurodegeneration. The aim of the study was to characterize these properties from different perspectives: (i) using the Kullback-Leibler divergence (KLD), a measure of non-stationarity derived from the continuous wavelet transform; and (ii) using the entropy of the recurrence point density () and the median of the recurrence point density (), two novel metrics based on recurrence quantification analysis. Approach. KLD, and were computed for 49 patients with dementia due to AD, 66 patients with MCI due to AD and 43 cognitively healthy controls from 60 s electroencephalographic (EEG) recordings with a 10 s sliding window with no overlap. Afterwards, we tested whether the measures reflected alterations to normal neuronal activity induced by MCI and AD. Main results. Our results showed that frequency-dependent alterations to normal dynamic behavior can be found in patients with MCI and AD, both in non-stationarity and recurrence structure. Patients with MCI showed signs of patterns of abnormal state recurrence in the theta (4-8 Hz) and beta (13-30 Hz) frequency bands that became more marked in AD. Moreover, abnormal non-stationarity patterns were found in MCI patients, but not in patients with AD in delta (1-4 Hz), alpha (8-13 Hz), and gamma (30-70 Hz). Significance. The alterations in normal levels of non-stationarity in patients with MCI suggest an initial increase in cortical activity during the development of AD. This increase could possibly be due to an impairment in neuronal inhibition that is not present during later stages. MCI and AD induce alterations to the recurrence structure of cortical activity, suggesting that normal state switching during rest may be affected by these pathologies.
The temporal evolution of functional connectivity (FC) within the confines of individual scans is nowadays often explored with functional neuroimaging. This is particularly true for resting-state; ...yet, FC-dynamics have also been investigated as subjects engage on numerous tasks. It is these research efforts that constitute the core of this survey. First, empirical observations on how FC differs between task and rest—independent of temporal scale—are reviewed, as they underscore how, despite overall preservation of network topography, the brain's FC does reconfigure in systematic ways to accommodate task demands. Next, reports on the relationships between instantaneous FC and perception/performance in subsequent trials are discussed. Similarly, research where different aspects of task-concurrent FC-dynamics are explored or utilized to predict ongoing mental states are also examined. The manuscript finishes with an incomplete list of challenges that hopefully fuels future work in this vibrant area of neuroscientific research. Overall, this review concludes that task-concurrent FC-dynamics, when properly characterized, are relevant to behavior, and that their translational value holds considerable promise.
•Functional connectivity reshapes efficiently when switching between rest and task.•Moment-to-moment FC can predict subsequent perceptual outcomes.•Task-concurrent dynamic-FC metrics have significant behavioral relevance.•Analytical and interpretational challenges of task dynamic-FC are discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In most material handling industries, input‐ and command‐shaping techniques are extensively used to transfer objects safely. In these techniques, most of the work assumes a single‐degree‐of‐freedom ...system with zero initial conditions, and some of these cases are not practical. In crane systems, a crane jib cannot be positioned exactly on top of the payload at the start of transfer motion, which forces the system to start with initial angles. Furthermore, when the hook is large and/or far from the payload, the system cannot be considered a single‐degree‐of‐freedom system. Not accounting for such conditions can create unwanted oscillations at the end of the motion. In this work, a closed‐form command shaping control of a double pendulum is suggested to eliminate the residual oscillations while considering nonzero initial angles. The equation of motion is derived and then solved to find the shaper constants analytically. This shaper has a selectable maneuvering time and ensures maximum cruising velocity. Several examples are implemented numerically and experimentally to evaluate the shaper's performance. Despite the nonzero initial conditions, the results showed that the shaper can effectively eliminate all induced vibrations at the end of the maneuver.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Aim
Altered mitochondrial function across various tissues is a key determinant of spaceflight‐induced physical deconditioning. In comparison to tissue biopsies, blood cell bioenergetics holds promise ...as a systemic and more readily accessible biomarker, which was evaluated during head‐down tilt bed rest (HDTBR), an established ground‐based analog for spaceflight‐induced physiological changes in humans. More specifically, this study explored the effects of HDTBR and an exercise countermeasure on mitochondrial respiration in peripheral blood mononuclear cells (PBMCs).
Methods
We subjected 24 healthy participants to a strict 30‐day HDTBR protocol. The control group (n = 12) underwent HDTBR only, while the countermeasure group (n = 12) engaged in regular supine cycling exercise followed by veno‐occlusive thigh cuffs post‐exercise for 6 h. We assessed routine blood parameters 14 days before bed rest, the respiratory capacity of PBMCs via high‐resolution respirometry, and citrate synthase activity 2 days before and at day 30 of bed rest. We confirmed PBMC composition by flow cytometry.
Results
The change of the PBMC maximal oxidative phosphorylation capacity (OXPHOS) amounted to an 11% increase in the countermeasure group, while it decreased by 10% in the control group (p = 0.04). The limitation of OXPHOS increased in control only while other respiratory states were not affected by either intervention. Correlation analysis revealed positive associations between white blood cells, lymphocytes, and basophils with PBMC bioenergetics in both groups.
Conclusion
This study reveals that a regular exercise countermeasure has a positive impact on PBMC mitochondrial function, confirming the potential application of blood cell bioenergetics for human spaceflight.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
To evaluate the effectiveness of an acute period of cognitive and physical rest on concussion.
Fifty consecutive patients with a diagnosis of concussions.
Participants were evaluated before (n = 25) ...and after (n = 25) a policy change that incorporated cognitive and physical rest. Patients in the rest group were withheld from activities, including classes, for the remainder of the injury day and the following day, whereas patients in the no-rest group were not provided any postinjury accommodations.
Patients were evaluated on a graded symptom checklist, Balance Error Scoring System, Standard Assessment of Concussion, and computerized neuropsychological tests. The number of days until each test achieved baseline values was compared between groups with independent-samples t test.
The no-rest group achieved asymptomatic status sooner than the rest group (5.2 ± 2.9 days and 3.9 ± 1.9 days, respectively; P = .047). There were no differences between groups for time to baseline values on the Balance Error Scoring System, Standard Assessment of Concussion, computerized neuropsychological tests, or time to clinical recovery.
A prescribed day of cognitive and physical rest was not effective in reducing postconcussion recovery time. These results agree with a previous study and suggest that light activity postconcussion may not be deleterious to the concussion recovery process.
The body naturally and continuously secretes sweat for thermoregulation during sedentary and routine activities at rates that can reflect underlying health conditions, including nerve damage, ...autonomic and metabolic disorders, and chronic stress. However, low secretion rates and evaporation pose challenges for collecting resting thermoregulatory sweat for non-invasive analysis of body physiology. Here we present wearable patches for continuous sweat monitoring at rest, using microfluidics to combat evaporation and enable selective monitoring of secretion rate. We integrate hydrophilic fillers for rapid sweat uptake into the sensing channel, reducing required sweat accumulation time towards real-time measurement. Along with sweat rate sensors, we integrate electrochemical sensors for pH, Cl
, and levodopa monitoring. We demonstrate patch functionality for dynamic sweat analysis related to routine activities, stress events, hypoglycemia-induced sweating, and Parkinson's disease. By enabling sweat analysis compatible with sedentary, routine, and daily activities, these patches enable continuous, autonomous monitoring of body physiology at rest.
Concussion is one of the most hotly debated topics in sports medicine today. Research surrounding concussion has experienced significant growth recently, especially in the areas of incidence, ...assessment, and recovery. However, there is limited research on the most effective rehabilitation approaches for this injury. This review evaluates the current literature for evidence for and against physical and cognitive rest and the emerging areas targeting vestibular, oculomotor, and pharmacologic interventions for the rehabilitation of sport-related concussion.
The hippocampus replays experiences during quiet rest periods, and this replay benefits subsequent memory. A critical open question is how memories are prioritized for this replay. We used functional ...magnetic resonance imaging (fMRI) pattern analysis to track item-level replay in the hippocampus during an awake rest period after participants studied 15 objects and completed a memory test. Objects that were remembered less well were replayed more during the subsequent rest period, suggesting a prioritization process in which weaker memories-memories most vulnerable to forgetting-are selected for replay. In a second session 12 hours later, more replay of an object during a rest period predicted better subsequent memory for that object. Replay predicted memory improvement across sessions only for participants who slept during that interval. Our results provide evidence that replay in the human hippocampus prioritizes weakly learned information, predicts subsequent memory performance, and relates to memory improvement across a delay with sleep.
While neuroimaging studies typically collapse data from many subjects, brain functional organization varies between individuals, and characterizing this variability is crucial for relating brain ...activity to behavioral phenotypes. Rest has become the default state for probing individual differences, chiefly because it is easy to acquire and a supposed neutral backdrop. However, the assumption that rest is the optimal condition for individual differences research is largely untested. In fact, other brain states may afford a better ratio of within- to between-subject variability, facilitating biomarker discovery. Depending on the trait or behavior under study, certain tasks may bring out meaningful idiosyncrasies across subjects, essentially enhancing the individual signal in networks of interest beyond what can be measured at rest. Here, we review theoretical considerations and existing work on how brain state influences individual differences in functional connectivity, present some preliminary analyses of within- and between-subject variability across conditions using data from the Human Connectome Project, and outline questions for future study.
•Rest is the default for studying individual differences in functional connectivity.•But certain tasks may improve the ratio of within- to between-subject variability.•We review work on how scan condition influences individual differences.•Preliminary results using HCP data show individual differences change with task.•Using certain tasks over rest may improve sensitivity of imaging-based biomarkers.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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