Global Measures Research Articles

COAALA: A Novel Approach to Understanding Extreme Stock–Bond Comovement

Abstract This article proposes a novel copula model to understand the dependence between extreme variations in stock and government bond returns. This model is used to introduce a tail-based extension of the safe haven concept, which we refer to as a tail risk dampener. Our findings reveal significant cross-country differences in stock–bond local tail dependence and tail risk dampening abilities. Some countries’ bond market can lessen the impact on portfolio returns of extreme negative stock returns, while for others no such negative tail comovement is found. This tail comovement is also not always aligned with global comovement between stocks and bonds. The article concludes that a comprehensive understanding of the comovement and the resulting diversification potential between stock and bond returns necessitates complementing global measures of dependence with local tail measures.

COVID-19 Stay-at-home mandates impacts daily ambulatory bout intensity and duration in elementary school-aged children: A wearable sensor based analysis

IntroductionSARS COVID-19 pandemic resulted in major changes to how daily life was conducted. Health officials instituted policies to decelerate the spread of the virus, resulting in changes in physical activity patterns of school-aged children. The aim of this study was to utilize a wearable activity monitor to assess ambulatory activity in elementary-school aged children in their home environment during a COVID-19 Stay-at-Home mandate. MethodsThis institutional review board approved research study was performed between April 3rd – May 1st of 2020 during which health officials issued several stay-at-home (shelter-in-place) orders. Participant recruitment was conducted using a convenience sample of 38 typically developing children. Participants wore a StepWatch Activity Monitor for one week and data were downloaded and analyzed to assess global ambulatory activity measures along with ambulatory bout intensity/duration. For comparison purposes, SAM data collected before the pandemic, of a group of 27 age-matched children from the same region of the United States, was included. Statistical analyses were performed comparing SAM variables between children abiding by a stay-at-home mandate (Stay-at-Home) versus the Historical cohort (alpha=0.05). ResultsStay-at-Home cohort took on average 3737 fewer daily total steps compared to the Historical cohort (p<0.001). Daily Total Ambulatory Time (TAT), across all days was significantly lower in the Stay-at-Home cohort compared to the Historical cohort (mean difference: 81.9 minutes, p=0.001). The Stay-at-Home cohort spent a significantly higher percentage of TAT in Easy intensity ambulatory activity (mean difference: 2%, p<0.001) and therefore a significantly lower percentage of TAT in Moderate+ intensity (mean difference: 2%, p<0.001). ConclusionsThe stay-at-home mandates resulted in lower PA levels in elementary school-aged children, beyond global measures to also bout intensity/duration. It appears that in-person school is a major contributor to achieving higher levels of PA and our study provides additional data for policymakers to consider for future decisions.

On the approximation of high-order binary Markov chains by parsimonious models

Abstract We consider two parsimonious models of binary high-order Markov chains and discover their ability to approximate arbitrary high-order Markov chains. Two types of global measures for approximation accuracy are introduced, theoretical and experimental results are obtained for these measures and for the considered parsimonious models. New consistent statistical parameter estimator is constructed for parsimonious model based on two-layer artificial neural network.

A many-objective evolutionary algorithm under diversity-first selection based framework

Many-objective optimization problems (MaOPs) have attracted wide attention. However, most solving methods prioritize the convergence or take the convergence and diversity into account. This causes the difficulty in balancing convergence and diversity of the population still remains, especially for these problems with irregular Pareto fronts. To this end, we propose a many-objective evolutionary algorithm under diversity-first selection based framework (DSFMO), which first emphasizes the diversity and then considers the convergence. Thus, DSFMO can drive individuals to approach the Pareto front from various directions, and further achieve the balance between convergence and diversity of the population. In this framework, we first construct a candidate pool by selecting these individuals with small crowded degree (i.e., good diversity), in which the crowded degree is evaluated by the global diversity measure based on the objective transferring. Then, the individual in the constructed candidate pool that has the best convergence is selected to enter the next generation, where the convergence is evaluated by the conditional convergence measure that considers the importance of boundary individuals and evolution status. The above two steps are repeatedly executed until the next generation population is formed. In addition, a space projection assisted mating selection is developed to select high-quality parents for variation and further enhance the exploration and exploitation ability of DSFMO. Experiments on 88 test instances have shown that DSFMO can perform best on most test instances. In other words, DSFMO outperforms its seven competitors in balancing convergence and diversity of the population.

A Longitudinal Study of the Effect of Memory on the Quality of life of European Adults and Older Adults

Among studies conceptualizing quality of life (QoL) as the subjective measure of one’s well-being, evidence suggests a link between cognitive impairment and diminished quality of life. However, the direction of the association is not clear, and most studies have employed a global measure of cognition, which can mask subtle domain-specific declines. In this study, we aim at examining the longitudinal associations between memory and QoL in a representative sample of adults and older adults in Europe and Israel, employing data from the Survey of Health, Ageing and Retirement in Europe (SHARE). The sample was composed by 56,616 respondents aged 50 or older at the beginning of the study period. A Parallel-Process Latent Growth Model (PP LGM) of memory and QoL conditioned on the effects of age, gender, educational level, physical inactivity, depressive symptomatology and social activity participation, was tested. Results displayed a trajectory of decline for both memory and QoL, with higher initial levels of memory associated with higher initial levels of QoL, and steeper decline in memory associated with steeper decline in QoL. Moreover, a positive effect of initial memory onto QoL trend over time was found, indicating that better memory is associated to better QoL in the future, but the opposite did not occur. Results also provide evidence of gender differences. All in all, this work found evidence supporting the longitudinal effect of memory on QoL, which may have consequences for intervention implementation, given that actions for alleviating age-related memory impairment could also have a positive impact onto older adults’ QoL.

Occupational stress among Norwegian physicians: A literature review of long-term prospective studies 2007-2019.

There are signs of increased stress at work among Norwegian physicians over the last decades, not least among general practitioners (GPs). In this review, we identify trends in both occupational stress and adverse work-related predictors of such stress and burnout in Norwegian physicians. We performed an extensive literature search using MEDLINE, Embase and PsycINFO. We included prospective and repeated cross-sectional studies of work stress among Norwegian physicians published in 2007-2019. Nine studies with observation periods of 1-20 years were included. Occupational stress (global measure) among all doctors decreased gradually from medical school to 20 years later. The prevalence of an effort-reward imbalance increased fourfold among GPs during the period 2010-2019. Five studies reported higher levels of occupational stress among female physicians than among their male colleagues. Work-home conflict levels increased after graduation until 10 years after leaving medical school and plateaued thereafter. Physicians who graduated in a later cohort reported lower levels of work-home conflict and less workplace violence. Work-home conflict, low colleague support, number of work hours and workload/low autonomy were all independent predictors of occupational stress. The reduction in occupational stress during the years after leaving medical school may result from increased competency in clinical work and decreased on-call work. The Co-ordination Act implemented in 2012 may explain the increase in occupational stress among GPs. These findings suggest that both reducing work-home conflict and increasing colleague support are important for doctors' well-being.

Comparison of Global and Daily Ratings of Associations between Anxiety and Depressive Behaviors and Impairment in Preschool-Aged Children.

Anxiety and depressive difficulties can emerge during early childhood and cause impairment in functioning. Anxiety and depressive behaviors and impairment are typically assessed with global questionnaires that require recall of children's behavior over an extended period which could reduce the accuracy of parent report of children's behavior and functioning. The current study compared parents' report of children's anxiety and depressive behaviors and impairment when evaluated with global measures versus a daily diary measure. Participants (N = 901 parents of 3-5-year-old children) completed global and daily measures of children's behavior and impairment during enrollment to the study. Global measures were completed at baseline and the 14 daily diary measures were completed consecutively for two weeks. Across most measures, daily associations between parent-reported anxiety and depressive behaviors and impairment were stronger compared to associations with global measures. These results suggest that daily measures may better capture links between young children's typical behavior and functioning compared to global measures. In addition, daily assessment might be more effective for measuring mild to moderate yet still impairing behaviors that may be missed on global reports that require longer periods of recall.

Heat and Acupuncture to Manage Osteoarthritis of the Knee (HARMOKnee): Protocol for an Effectiveness-Implementation Hybrid Randomized Controlled Trial.

Knee osteoarthritis (KOA) is one of most prevalent and fastest-growing causes of pain, impaired mobility, and poor quality of life in the rapidly aging population worldwide. There is a lack of high-quality evidence on the efficacy of traditional Chinese medicine (TCM), particularly acupuncture, and a lack of KOA practice guidelines that are tailored to unique population demographics and tropical climates. Our HARMOKnee (Heat and Acupuncture to Manage Osteoarthritis of the Knee) trial aims to address these gaps by evaluating the short- and medium-term clinical and cost-effectiveness of acupuncture with heat therapy in addition to standard care, compared to standard care alone. Through a robust process and economic evaluation, we aim to inform evidence-based practice for patients with KOA to facilitate the large-scale implementation of a comprehensive and holistic model of care that harmonizes elements of Western medicine and TCM. We hypothesize that acupuncture with heat therapy as an adjunct to standard care is clinically more effective than standard care alone. A multicenter, pragmatic, parallel-arm, single-blinded, effectiveness-implementation hybrid randomized controlled trial will be conducted. We intend to recruit 100 patients with KOA randomized to either the control arm (standard care only) or intervention arm (acupuncture with heat therapy, in addition to standard care). The inclusion criteria are being a community ambulator and having primary KOA, excluding patients with secondary arthritis or previous knee replacements. The primary outcome measure is the Knee Osteoarthritis Outcome Score at 6 weeks. Secondary outcome measures include psychological, physical, quality of life, satisfaction, and global outcome measures at 6, 12, and 26 weeks. A mixed method approach through an embedded process evaluation will facilitate large-scale implementation. An economic evaluation will be performed to assess financial sustainability. Patient enrollment has been ongoing since August 2022. The recruitment process is anticipated to conclude by July 2024, and the findings will be analyzed and publicized as they are obtained. As of November 6, 2023, our patient enrollment stands at 65 individuals. The findings of our HARMOKnee study will contribute substantial evidence to the current body of literature regarding the effectiveness of acupuncture treatment for KOA. Additionally, we aim to facilitate the creation of standardized national guidelines for evidence-based practice that are specifically tailored to our unique population demographics. Furthermore, we seek to promote the adoption and integration of acupuncture and heat therapy into existing treatment models. ClinicalTrials.gov NCT05507619; https://clinicaltrials.gov/study/NCT05507619. DERR1-10.2196/54352.

The impact of COVID-19 on deaths from dementia and Alzheimer’s disease in Chile: an analysis of panel data for 16 regions, 2017–2022

Although several studies have documented the detrimental impacts of global COVID-19 containment measures on individuals with Alzheimer's disease and dementia, a comprehensive analysis of mortality rates for these conditions within the Chilean population is notably lacking. This study aimed to analyze the impact of COVID-19 on mortality rates among individuals with dementia and Alzheimer's disease in Chile. A retrospective longitudinal cross-sectional study was conducted, considering mortality data for specific mental health conditions during the pre-pandemic and pandemic contexts of COVID-19 in Chile. Quantile regression techniques were employed to analyze the existence of differences between the two periods, while non-observable heterogeneity models for panel data methods were used to evaluate the effect of COVID-19 mortality on crude mortality rates. Statistically significant differences were observed in the number of deaths from dementia and Alzheimer's disease between the pre-pandemic and COVID-19 pandemic periods. Specifically, crude mortality rates decreased by 10% (-0.10 [95% CI:-0.16,-0.05]) during the pandemic period. Furthermore, the number of deaths from COVID-19 during the pandemic period has a very weak incidence of deaths from mental health conditions such as dementia and Alzheimer's. Specifically, a unit percentage increase in confirmed cases from COVID-19 would result in a 7% (-0.07 [95% CI:-0.13,-0.001]) decrease in the number of deaths from dementia and Alzheimer's. These findings are supported by the application of panel regression with one-way random effects models. The study findings indicate a reduction in mortality rates attributed to dementia and Alzheimer's disease during the COVID-19 pandemic in Chile. This decline could be attributed to the potential underreporting of mental illness as the cause of death during the pandemic period. Several studies have highlighted that approximately 30% of death certificates fail to document the presence of a dementia syndrome. Moreover, the cause of death recorded for individuals with mental health conditions may be influenced by the physician's familiarity with the patient or reflect the prevailing approach to managing end-stage dementia patients. This work received no funding.

EAACI guidelines on environmental science for allergy and asthma: The impact of short-term exposure to outdoor air pollutants on asthma-related outcomes and recommendations for mitigation measures.

The EAACI Guidelines on the impact of short-term exposure to outdoor pollutants on asthma-related outcomes provide recommendations for prevention, patient care and mitigation in a framework supporting rational decisions for healthcare professionals and patients to individualize and improve asthma management and for policymakers and regulators as an evidence-informed reference to help setting legally binding standards and goals for outdoor air quality at international, national and local levels. The Guideline was developed using the GRADE approach and evaluated outdoor pollutants referenced in the current Air Quality Guideline of the World Health Organization as single or mixed pollutants and outdoor pesticides. Short-term exposure to all pollutants evaluated increases the risk of asthma-related adverse outcomes, especially hospital admissions and emergency department visits (moderate certainty of evidence at specific lag days). There is limited evidence for the impact of traffic-related air pollution and outdoor pesticides exposure as well as for the interventions to reduce emissions. Due to the quality of evidence, conditional recommendations were formulated for all pollutants and for the interventions reducing outdoor air pollution. Asthma management counselled by the current EAACI guidelines can improve asthma-related outcomes but global measures for clean air are needed to achieve significant impact.

Habitat suitability model of future coral reef region in the Halmahera Waters under the projection of environmental pressures from future climate change and coastal pollution

The coral reef region of the Halmahera waters situated within the tropical area of the coral triangle, covers approximately 193,126 km2, with coral reef habitats occupying roughly 958.47 km2. The coral reefs in Halmahera waters are essential for ecosystem services and local fisheries. However, they are at risk from climate change and coastal pollution. This study aimed to develop habitat suitability models for coral reefs in the Halmahera waters under future climate change scenarios. MaxEnt modeling was employed to project suitability for the coral Acropora spp. using occurrence data. Suitability projections were made for 2050 under IPCC RCP 2.6, 6.0, and 8.5 scenarios, assuming no measures are taken to mitigate coastal water pollution. Environmental factors considered in the modeling included temperature, salinity, current velocity, pH, sunlight penetration, and chlorophyll levels. Results demonstrated a significant decline in habitat suitability, with an 85% loss of highly suitable areas under RCP 2.6 – 8.5 compared to current conditions (741 km2). Chlorophyll levels, a marker of coastal pollution, were predicted to be the most influential factor, followed by temperature and salinity. The findings highlight the need to reduce global carbon emissions and implement conservation measures to mitigate coastal water pollution in preserving coral reef habitats.

Effect of COVID-19 and Its Vaccine: Hematological and Immunological Study of Recovered Individuals Based on Gender

Abstract Background: The necessary urgent global response measures were implemented to contain the rapid spread of coronavirus disease 2019 (COVID-19). Vaccination has been the most effective way to combat this pandemic. Objective: The aim of the current study was to evaluate the hematological parameters and COVID-19-specific antibodies in a healthy population with different COVID-19 and vaccination backgrounds, taking gender into account. Materials and Methods: The study involved 80 healthy adults who were categorized into four groups based on their COVID-19 and vaccination status. The male and female categorization was later added to these groups. Blood samples were collected and analyzed for COVID-19-specific antibodies, IgG and IgM, and complete blood count parameters. The samples were collected in Karbala, Iraq. Results: The results showed that the IgG levels of IV and NIV subsets were higher than INV NINV subsets at P value &lt; 0.001. No significant differences were found in white blood cell parameters except for lymphocytes, neutrophils, and their ratio between the four groups. However, when gender was taken into account, few significant differences were observed in white blood cells, lymphocytes, and neutrophils between the groups. The platelet indices showed no significant changes within the individual groups or genders. Red blood cell variables also showed no significant changes between groups, but variations in red blood cells, hematocrit, and hemoglobin were found for each gender-divided group specifically (P value &lt; 0.001). Conclusion: The present study concludes that vaccination mimics infection. No changes were observed for most hematological parameters between the four explored subsets. However, the study revealed gender-specific responses to red blood cell counts and other related parameters, reinforcing the importance of complete blood count testing and advocating a deeper exploration into gender-specific responses, especially for patients with specific hematological conditions.

Autism-Linked Traits and Creativity: Empathy and Sensory Sensitivities in Children Predict Creative Activities and Openness

ABSTRACT Several studies have investigated the relationship between autism-linked traits and creativity in adults across the general population, but far fewer in developmental populations. Here we examined how creativity in children is linked to the autism-linked traits of empathy (i.e. ability to understand and engage with another’s emotions and feelings) and sensory sensitivities (i.e. over/under-responding to incoming sensory stimuli). Our study collected data from 659 children aged 6–12, treating autism-linked traits as global and domain level features. We collected two sets of creativity data, focussing on a personality trait associated with creativity (Openness to experience; with two facets of Ideas and Aesthetics) and engagement in creative activities (with two facets of Performance and Art). After controlling for age and gender, our global measure of empathy predicted all four creativity outcomes, especially Ideas (strongly linked to curiosity, inventiveness and idea generation). Similarly, children with greater Emotional empathy displayed more creative across all four creativity outcomes, particularly creative activities (Performance, Art). Social-cognitive empathy was associated with both Openness facets, particularly Ideas. Finally, we found that sensory sensitivities predicted several trivially-size effects. Our study contributes to a broader understanding of how autism-linked traits in the general population interact with features of creativity in children.

Connectedness and co-movement between dirty energy, clean energy and global COVOL

This paper examines dynamic connectedness and co-movement between dirty energy, clean energy and the global COVOL measure of Engle and Campos-Martins (2023) between January 2015 and May 2023 based on aggregated connectedness and wavelet coherence approaches. Our results show that COVOL and dirty energy are more closely linked in times of COVID-19 and geopolitical instability, while clean energy is more isolated from geopolitical events. Moreover, the coherence between dirty and clean energy markets is weaker after 2020, consistent with a decoupling hypothesis between dirty energy and clean energy.

Preliminary Evidence for Global Properties in Human Listeners During Natural Auditory Scene Perception.

Theories of auditory and visual scene analysis suggest the perception of scenes relies on the identification and segregation of objects within it, resembling a detail-oriented processing style. However, a more global process may occur while analyzing scenes, which has been evidenced in the visual domain. It is our understanding that a similar line of research has not been explored in the auditory domain; therefore, we evaluated the contributions of high-level global and low-level acoustic information to auditory scene perception. An additional aim was to increase the field's ecological validity by using and making available a new collection of high-quality auditory scenes. Participants rated scenes on 8 global properties (e.g., open vs. enclosed) and an acoustic analysis evaluated which low-level features predicted the ratings. We submitted the acoustic measures and average ratings of the global properties to separate exploratory factor analyses (EFAs). The EFA of the acoustic measures revealed a seven-factor structure explaining 57% of the variance in the data, while the EFA of the global property measures revealed a two-factor structure explaining 64% of the variance in the data. Regression analyses revealed each global property was predicted by at least one acoustic variable (R2 = 0.33-0.87). These findings were extended using deep neural network models where we examined correlations between human ratings of global properties and deep embeddings of two computational models: an object-based model and a scene-based model. The results support that participants' ratings are more strongly explained by a global analysis of the scene setting, though the relationship between scene perception and auditory perception is multifaceted, with differing correlation patterns evident between the two models. Taken together, our results provide evidence for the ability to perceive auditory scenes from a global perspective. Some of the acoustic measures predicted ratings of global scene perception, suggesting representations of auditory objects may be transformed through many stages of processing in the ventral auditory stream, similar to what has been proposed in the ventral visual stream. These findings and the open availability of our scene collection will make future studies on perception, attention, and memory for natural auditory scenes possible.

Epigenetic scores of blood-based proteins as biomarkers of general cognitive function and brain health

BackgroundEpigenetic Scores (EpiScores) for blood protein levels have been associated with disease outcomes and measures of brain health, highlighting their potential usefulness as clinical biomarkers. They are typically derived via penalised regression, whereby a linear weighted sum of DNA methylation (DNAm) levels at CpG sites are predictive of protein levels. Here, we examine 84 previously published protein EpiScores as possible biomarkers of cross-sectional and longitudinal measures of general cognitive function and brain health, and incident dementia across three independent cohorts.ResultsUsing 84 protein EpiScores as candidate biomarkers, associations with general cognitive function (both cross-sectionally and longitudinally) were tested in three independent cohorts: Generation Scotland (GS), and the Lothian Birth Cohorts of 1921 and 1936 (LBC1921 and LBC1936, respectively). A meta-analysis of general cognitive functioning results in all three cohorts identified 18 EpiScore associations (absolute meta-analytic standardised estimates ranged from 0.03 to 0.14, median of 0.04, PFDR < 0.05). Several associations were also observed between EpiScores and global brain volumetric measures in the LBC1936. An EpiScore for the S100A9 protein (a known Alzheimer disease biomarker) was associated with general cognitive functioning (meta-analytic standardised beta: − 0.06, P = 1.3 × 10−9), and with time-to-dementia in GS (Hazard ratio 1.24, 95% confidence interval 1.08–1.44, P = 0.003), but not in LBC1936 (Hazard ratio 1.11, P = 0.32).ConclusionsEpiScores might make a contribution to the risk profile of poor general cognitive function and global brain health, and risk of dementia, however these scores require replication in further studies.

Assessing brain involvement in Fabry disease with deep learning and the brain-age paradigm.

While neurological manifestations are core features of Fabry disease (FD), quantitative neuroimaging biomarkers allowing to measure brain involvement are lacking. We used deep learning and the brain-age paradigm to assess whether FD patients' brains appear older than normal and to validate brain-predicted age difference (brain-PAD) as a possible disease severity biomarker. MRI scans of FD patients and healthy controls (HCs) from a single Institution were, retrospectively, studied. The Fabry stabilization index (FASTEX) was recorded as a measure of disease severity. Using minimally preprocessed 3D T1-weighted brain scans of healthy subjects from eight publicly available sources (N = 2160; mean age = 33 years [range 4-86]), we trained a model predicting chronological age based on a DenseNet architecture and used it to generate brain-age predictions in the internal cohort. Within a linear modeling framework, brain-PAD was tested for age/sex-adjusted associations with diagnostic group (FD vs. HC), FASTEX score, and both global and voxel-level neuroimaging measures. We studied 52 FD patients (40.6 ± 12.6 years; 28F) and 58 HC (38.4 ± 13.4 years; 28F). The brain-age model achieved accurate out-of-sample performance (mean absolute error = 4.01 years, R2 = .90). FD patients had significantly higher brain-PAD than HC (estimated marginal means: 3.1 vs. -0.1, p = .01). Brain-PAD was associated with FASTEX score (B = 0.10, p = .02), brain parenchymal fraction (B = -153.50, p = .001), white matter hyperintensities load (B = 0.85, p = .01), and tissue volume reduction throughout the brain. We demonstrated that FD patients' brains appear older than normal. Brain-PAD correlates with FD-related multi-organ damage and is influenced by both global brain volume and white matter hyperintensities, offering a comprehensive biomarker of (neurological) disease severity.

Parental sensitivity and intrusiveness with mothers and fathers: Associations between parental behavioral activation/inhibition and infant temperament.

Understanding the factors contributing to sensitive parenting is crucial to optimize infant social and emotional functioning. Research has supported the association between parents' personality and parenting quality, but findings are inconsistent when examining various global personality measures. Further, it is likely that the interaction between parent-level (e.g., personality) and infant-level characteristics (e.g., temperament) are more strongly associated with caregiving quality. Most studies examining predictors of parenting quality have only included mothers, compared to fathers. The current study examined the interaction between parental personality and infant temperament and associations with parental sensitivity and intrusiveness with mothers and fathers. The participants included families (n=102) when the infants were 4, 6, and 8months old. Using parent report measures and a face-to-face play task, significant main effects of maternal behavioral inhibition on parenting behaviors were observed for mothers. A Behavioral Activation X Infant Negative Reactivity interaction predicted both maternal sensitivity and intrusiveness, whereas a Behavioral Inhibition X Infant Surgency predicted paternal intrusiveness. In summary, the results revealed support for the goodness-of-fit perspective between parents' personality and infant temperament.

Impaired long-range excitatory time scale predicts abnormal neural oscillations and cognitive deficits in Alzheimer’s disease

BackgroundAlzheimer’s disease (AD) is the most common form of dementia, progressively impairing cognitive abilities. While neuroimaging studies have revealed functional abnormalities in AD, how these relate to aberrant neuronal circuit mechanisms remains unclear. Using magnetoencephalography imaging we documented abnormal local neural synchrony patterns in patients with AD. To identify global abnormal biophysical mechanisms underlying the spatial and spectral electrophysiological patterns in AD, we estimated the parameters of a biophysical spectral graph model (SGM).MethodsSGM is an analytic neural mass model that describes how long-range fiber projections in the brain mediate the excitatory and inhibitory activity of local neuronal subpopulations. Unlike other coupled neuronal mass models, the SGM is linear, available in closed-form, and parameterized by a small set of biophysical interpretable global parameters. This facilitates their rapid and unambiguous inference which we performed here on a well-characterized clinical population of patients with AD (N = 88, age = 62.73 +/- 8.64 years) and a cohort of age-matched controls (N = 88, age = 65.07 +/- 9.92 years).ResultsPatients with AD showed significantly elevated long-range excitatory neuronal time scales, local excitatory neuronal time scales and local inhibitory neural synaptic strength. The long-range excitatory time scale had a larger effect size, compared to local excitatory time scale and inhibitory synaptic strength and contributed highest for the accurate classification of patients with AD from controls. Furthermore, increased long-range time scale was associated with greater deficits in global cognition.ConclusionsThese results demonstrate that long-range excitatory time scale of neuronal activity, despite being a global measure, is a key determinant in the local spectral signatures and cognition in the human brain, and how it might be a parsimonious factor underlying altered neuronal activity in AD. Our findings provide new insights into mechanistic links between abnormal local spectral signatures and global connectivity measures in AD.

Age-related changes in human brain functional connectivity using graph theory and machine learning techniques in resting-state fMRI data.

Aging is the basis of neurodegeneration and dementia that affects each endemic in the body.Normal aging in the brain is associated with progressive slowdown and disruptions in various abilities such as motor ability, cognitive impairment, decreasing information processing speed, attention, and memory. With the aggravation of global aging, more research focuses on brain changes in the elderly adult. The graph theory, in combination with functional magnetic resonance imaging (fMRI), makes it possible to evaluate the brain network functional connectivity patterns in different conditions with brain modeling. We have evaluated the brain network communication model changes in three different age groups (including 8 to 15years, 25 to 35years, and 45 to 75years) in lifespan pilot data from the human connectome project (HCP). Initially, Pearson correlation-based connectivity networks were calculated and thresholded. Then, network characteristics were compared between the three age groups by calculating the global and local graph measures. In the resting state brain network, we observed decreasing global efficiency and increasing transitivity with age. Also, brain regions, including the amygdala, putamen, hippocampus, precuneus, inferior temporal gyrus, anterior cingulate gyrus, and middle temporal gyrus, were selected as the most affected brain areas with age through statistical tests and machine learning methods. Using feature selection methods, including Fisher score and Kruskal-Wallis, we were able to classify three age groups using SVM, KNN, and decision-tree classifier. The best classification accuracy is in the combination of Fisher score and decision tree classifier obtained, which was 82.2%. Thus, by examining the measures of functional connectivity using graph theory, we will be able to explore normal age-related changes in the human brain, which can be used as a tool to monitor health with age.