Brain health in diverse settings: How age, demographics and cognition shape brain function

Diversity in brain health is influenced by individual differences in demographics and cognition. However, most studies on brain health and diseases have typically controlled for these factors rather than explored their potential to predict brain signals. Here, we assessed the role of individual differences in demographics (age, sex, and education; n = 1298) and cognition (n = 725) as predictors of different metrics usually used in case-control studies. These included power spectrum and aperiodic (1/f slope, knee, offset) metrics, as well as complexity (fractal dimension estimation, permutation entropy, Wiener entropy, spectral structure variability) and connectivity (graph-theoretic mutual information, conditional mutual information, organizational information) from the source space resting-state EEG activity in a diverse sample from the global south and north populations. Brain-phenotype models were computed using EEG metrics reflecting local activity (power spectrum and aperiodic components) and brain dynamics and interactions (complexity and graph-theoretic measures). Electrophysiological brain dynamics were modulated by individual differences despite the varied methods of data acquisition and assessments across multiple centers, indicating that results were unlikely to be accounted for by methodological discrepancies. Variations in brain signals were mainly influenced by age and cognition, while education and sex exhibited less importance. Power spectrum activity and graph-theoretic measures were the most sensitive in capturing individual differences. Older age, poorer cognition, and being male were associated with reduced alpha power, whereas older age and less education were associated with reduced network integration and segregation. Findings suggest that basic individual differences impact core metrics of brain function that are used in standard case-control studies. Considering individual variability and diversity in global settings would contribute to a more tailored understanding of brain function.

Viscous dynamics associated with hypoexcitation and structural disintegration in neurodegeneration via generative whole-brain modeling

INTRODUCTION

Alzheimer's disease (AD) and behavioral variant frontotemporal dementia (bvFTD) lack mechanistic biophysical modeling in diverse, underrepresented populations. Electroencephalography (EEG) is a high temporal resolution, cost-effective technique for studying dementia globally, but lacks mechanistic models and produces non-replicable results.

METHODS

We developed a generative whole-brain model that combines EEG source-level metaconnectivity, anatomical priors, and a perturbational approach. This model was applied to Global South participants (AD, bvFTD, and healthy controls).

RESULTS

Metaconnectivity outperformed pairwise connectivity and revealed more viscous dynamics in patients, with altered metaconnectivity patterns associated with multimodal disease presentation. The biophysical model showed that connectome disintegration and hypoexcitability triggered altered metaconnectivity dynamics and identified critical regions for brain stimulation. We replicated the main results in a second subset of participants for validation with unharmonized, heterogeneous recording settings.

DISCUSSION

The results provide a novel agenda for developing mechanistic model-inspired characterization and therapies in clinical, translational, and computational neuroscience settings.

Elevating understanding: Linking high-altitude hypoxia to brain aging through EEG functional connectivity and spectral analyses

High-altitude hypoxia triggers brain function changes reminiscent of those in healthy aging and Alzheimer's disease, compromising cognition and executive functions. Our study sought to validate high-altitude hypoxia as a model for assessing brain activity disruptions akin to aging. We collected EEG data from 16 healthy volunteers during acute high-altitude hypoxia (at 4,000 masl) and at sea level, focusing on relative changes in power and aperiodic slope of the EEG spectrum due to hypoxia. Additionally, we examined functional connectivity using wPLI, and functional segregation and integration using graph theory tools. High altitude led to slower brain oscillations, that is, increased δ and reduced α power, and flattened the 1/f aperiodic slope, indicating higher electrophysiological noise, akin to healthy aging. Notably, functional integration strengthened in the θ band, exhibiting unique topographical patterns at the subnetwork level, including increased frontocentral and reduced occipitoparietal integration. Moreover, we discovered significant correlations between subjects' age, 1/f slope, θ band integration, and observed robust effects of hypoxia after adjusting for age. Our findings shed light on how reduced oxygen levels at high altitudes influence brain activity patterns resembling those in neurodegenerative disorders and aging, making high-altitude hypoxia a promising model for comprehending the brain in health and disease.

High-order brain interactions in ketamine during rest and task: A double-blinded cross-over design using portable EEG

In a double-blinded cross-over design, 30 adults (mean age = 25.57, SD = 3.74; all male) were administered racemic ketamine and compared against saline infusion as a control. Both task-driven (auditory oddball paradigm) and resting-state EEG were recorded. HOI were computed using advanced multivariate information theory tools, allowing us to quantify nonlinear statistical dependencies between all possible electrode combinations. Results: Ketamine increased redundancy in brain dynamics, most significantly in the alpha frequency band. Redundancy was more evident during the resting state, associated with a shift in conscious states towards more dissociative tendencies. Furthermore, in the task-driven context (auditory oddball), the impact of ketamine on redundancy was more significant for predictable (standard stimuli) compared to deviant ones. Finally, associations were observed between ketamine's HOI and experiences of derealization. Conclusions: Ketamine appears to increase redundancy and genuine HOI across metrics, suggesting these effects correlate with consciousness alterations towards dissociation. HOI represents an innovative method to combine all signal spatial interactions obtained from low-density dry EEG in drug interventions, as it is the only approach that exploits all possible combinations from different electrodes. This research emphasizes the potential of complexity measures coupled with portable EEG devices in monitoring shifts in consciousness, especially when paired with low-density configurations, paving the way for better understanding and monitoring of pharmacological-induced changes.

The BrainLat project, a multimodal neuroimaging dataset of neurodegeneration from underrepresented backgrounds

The Latin American Brain Health Institute (BrainLat) has released a unique multimodal neuroimaging dataset of 780 participants from Latin American. The dataset includes 530 patients with neurodegenerative diseases such as Alzheimer's disease (AD), behavioral variant frontotemporal dementia (bvFTD), multiple sclerosis (MS), Parkinson's disease (PD), and 250 healthy controls (HCs). This dataset (62.7 ± 9.5 years, age range 21-89 years) was collected through a multicentric effort across five Latin American countries to address the need for affordable, scalable, and available biomarkers in regions with larger inequities. The BrainLat is the first regional collection of clinical and cognitive assessments, anatomical magnetic resonance imaging (MRI), resting-state functional MRI (fMRI), diffusion-weighted MRI (DWI), and high density resting-state electroencephalography (EEG) in dementia patients. In addition, it includes demographic information about harmonized recruitment and assessment protocols. The dataset is publicly available to encourage further research and development of tools and health applications for neurodegeneration based on multimodal neuroimaging, promoting the assessment of regional variability and inclusion of underrepresented participants in research.

Harmonized multi-metric and multi-centric assessment of EEG source space connectivity for dementia characterization

Introduction

Harmonization protocols that address batch effects and cross-site methodological differences in multi-center studies are critical for strengthening electroencephalography (EEG) signatures of functional connectivity (FC) as potential dementia biomarkers.

Methods

We implemented an automatic processing pipeline incorporating electrode layout integrations, patient-control normalizations, and multi-metric EEG source space connectomics analyses.

Results

Spline interpolations of EEG signals onto a head mesh model with 6067 virtual electrodes resulted in an effective method for integrating electrode layouts. Z-score transformations of EEG time series resulted in source space connectivity matrices with high bilateral symmetry, reinforced long-range connections, and diminished short-range functional interactions. A composite FC metric allowed for accurate multicentric classifications of Alzheimer's disease and behavioral variant frontotemporal dementia.

Discussion

Harmonized multi-metric analysis of EEG source space connectivity can address data heterogeneities in multi-centric studies, representing a powerful tool for accurately characterizing dementia.

DIVA Meets EEG: Model Validation Using Formant-Shift Reflex

The neurocomputational model 'Directions into Velocities of Articulators' (DIVA) was developed to account for various aspects of normal and disordered speech production and acquisition. The neural substrates of DIVA were established through functional magnetic resonance imaging (fMRI), providing physiological validation of the model. This study introduces DIVA_EEG an extension of DIVA that utilizes electroencephalography (EEG) to leverage the high temporal resolution and broad availability of EEG over fMRI. For the development of DIVA_EEG, EEG-like signals were derived from original equations describing the activity of the different DIVA maps. Synthetic EEG associated with the utterance of syllables was generated when both unperturbed and perturbed auditory feedback (first formant perturbations) were simulated. The cortical activation maps derived from synthetic EEG closely resembled those of the original DIVA model. To validate DIVA_EEG, the EEG of individuals with typical voices (N = 30) was acquired during an altered auditory feedback paradigm. The resulting empirical brain activity maps significantly overlapped with those predicted by DIVA_EEG. In conjunction with other recent model extensions, DIVA_EEG lays the foundations for constructing a complete neurocomputational framework to tackle vocal and speech disorders, which can guide model-driven personalized interventions.

Social and non-social working memory in neurodegeneration

Although social functioning relies on working memory, whether a social-specific mechanism exists remains unclear. This undermines the characterization of neurodegenerative conditions with both working memory and social deficits. We assessed working memory domain-specificity across behavioral, electrophysiological, and neuroimaging dimensions in 245 participants. A novel working memory task involving social and non-social stimuli with three load levels was assessed across controls and different neurodegenerative conditions with recognized impairments in: working memory and social cognition (behavioral-variant frontotemporal dementia); general cognition (Alzheimer's disease); and unspecific patterns (Parkinson's disease). We also examined resting-state theta oscillations and functional connectivity correlates of working memory domain-specificity. Results in controls and all groups together evidenced increased working memory demands for social stimuli associated with frontocinguloparietal theta oscillations and salience network connectivity. Canonical frontal theta oscillations and executive-default mode network anticorrelation indexed non-social stimuli. Behavioral-variant frontotemporal dementia presented generalized working memory deficits related to posterior theta oscillations, with social stimuli linked to salience network connectivity. In Alzheimer's disease, generalized working memory impairments were related to temporoparietal theta oscillations, with non-social stimuli linked to the executive network. Parkinson's disease showed spared working memory performance and canonical brain correlates. Findings support a social-specific working memory and related disease-selective pathophysiological mechanisms.

Source space connectomics of neurodegeneration: One-metric approach does not fit all

Brain functional connectivity in dementia has been assessed with dissimilar EEG connectivity metrics and estimation procedures, thereby increasing results' heterogeneity. In this scenario, joint analyses integrating information from different metrics may allow for a more comprehensive characterization of brain functional interactions in different dementia subtypes. To test this hypothesis, resting-state electroencephalogram (rsEEG) was recorded in individuals with Alzheimer's Disease (AD), behavioral variant frontotemporal dementia (bvFTD), and healthy controls (HCs). Whole-brain functional connectivity was estimated in the EEG source space using 101 different types of functional connectivity, capturing linear and nonlinear interactions in both time and frequency-domains. Multivariate machine learning and progressive feature elimination was run to discriminate AD from HCs, and bvFTD from HCs, based on joint analyses of i) EEG frequency bands, ii) complementary frequency-domain metrics (e.g., instantaneous, lagged, and total connectivity), and iii) time-domain metrics with different linearity assumption (e.g., Pearson correlation coefficient and mutual information). <10% of all possible connections were responsible for the differences between patients and controls, and atypical connectivity was never captured by >1/4 of all possible connectivity measures. Joint analyses revealed patterns of hypoconnectivity (patientsHCs) in both groups was mainly identified in frontotemporal regions. These atypicalities were differently captured by frequency- and time-domain connectivity metrics, in a bandwidth-specific fashion. The multi-metric representation of source space whole-brain functional connectivity evidenced the inadequacy of single-metric approaches, and resulted in a valid alternative for the selection problem in EEG connectivity. These joint analyses reveal patterns of brain functional interdependence that are overlooked with single metrics approaches, contributing to a more reliable and interpretable description of atypical functional connectivity in neurodegeneration.

Model-based whole-brain perturbational landscape of neurodegenerative diseases

The treatment of neurodegenerative diseases is hindered by lack of interventions capable of steering multimodal whole-brain dynamics towards patterns indicative of preserved brain health. To address this problem, we combined deep learning with a model capable of reproducing whole-brain functional connectivity in patients diagnosed with Alzheimer's disease (AD) and behavioral variant frontotemporal dementia (bvFTD). These models included disease-specific atrophy maps as priors to modulate local parameters, revealing increased stability of hippocampal and insular dynamics as signatures of brain atrophy in AD and bvFTD, respectively. Using variational autoencoders, we visualized different pathologies and their severity as the evolution of trajectories in a low-dimensional latent space. Finally, we perturbed the model to reveal key AD- and bvFTD-specific regions to induce transitions from pathological to healthy brain states. Overall, we obtained novel insights on disease progression and control by means of external stimulation, while identifying dynamical mechanisms that underlie functional alterations in neurodegeneration.

Temporal Irreversibility of Large-Scale Brain Dynamics in Alzheimer's Disease

Healthy brain dynamics can be understood as the emergence of a complex system far from thermodynamic equilibrium. Brain dynamics are temporally irreversible and thus establish a preferred direction in time (i.e., arrow of time). However, little is known about how the time-reversal symmetry of spontaneous brain activity is affected by Alzheimer's disease (AD). We hypothesized that the level of irreversibility would be compromised in AD, signaling a fundamental shift in the collective properties of brain activity toward equilibrium dynamics. We investigated the irreversibility from resting-state fMRI and EEG data in male and female human patients with AD and elderly healthy control subjects (HCs). We quantified the level of irreversibility and, thus, proximity to nonequilibrium dynamics by comparing forward and backward time series through time-shifted correlations. AD was associated with a breakdown of temporal irreversibility at the global, local, and network levels, and at multiple oscillatory frequency bands. At the local level, temporoparietal and frontal regions were affected by AD. The limbic, frontoparietal, default mode, and salience networks were the most compromised at the network level. The temporal reversibility was associated with cognitive decline in AD and gray matter volume in HCs. The irreversibility of brain dynamics provided higher accuracy and more distinctive information than classical neurocognitive measures when differentiating AD from control subjects. Findings were validated using an out-of-sample cohort. Present results offer new evidence regarding pathophysiological links between the entropy generation rate of brain dynamics and the clinical presentation of AD, opening new avenues for dementia characterization at different levels.SIGNIFICANCE STATEMENT By assessing the irreversibility of large-scale dynamics across multiple brain signals, we provide a precise signature capable of distinguishing Alzheimer's disease (AD) at the global, local, and network levels and different oscillatory regimes. Irreversibility of limbic, frontoparietal, default-mode, and salience networks was the most compromised by AD compared with more sensory-motor networks. Moreover, the time-irreversibility properties associated with cognitive decline and atrophy outperformed and complemented classical neurocognitive markers of AD in predictive classification performance. Findings were generalized and replicated with an out-of-sample validation procedure. We provide novel multilevel evidence of reduced irreversibility in AD brain dynamics that has the potential to open new avenues for understating neurodegeneration in terms of the temporal asymmetry of brain dynamics.

Scope for growth and dietary needs of Mediteranean Pinnids maintained in captivity

Background

The measurement of the energy available for growth (scope of growth, SFG) can be used in bivalves to make a long-term prediction in a short-term experiment of the condition of the individual. In order to tackle the best conditions for captive maintenance of Mediterranean Pinnids, a SFG study was conducted using Pinna rudis as a model species. Three diets were examined to test the viability of live microalgae and commercial products: i) a control diet using 100% of live microalgae based on the species Isochrysis galbana (t-ISO), ii) a 100% of commercial microalgae diet based on the product Shellfish Diet 1800®, and iii) a 50/50% mix diet of I. galbana (t-ISO) and Shellfish Diet 1800®.

Results

SFG results showed significant differences among diets in the physiological functions measured and suggested lower acceptability and digestibility of the commercial product. Negative SFG values were obtained for the commercial diet which indicates that it should be rejected for both Pinnid maintenance. The mixed diet showed improved physiological performance compared to the commercial diet, resulting in a higher SFG that had no significant differences with the control diet. However, in the long-term, the lower digestibility of the mixed diet compared to the control diet could lead to a deterioration of individuals’ conditions and should be considered cautiously.

Conclusions

This work represents the first case study of SFG in Pinna spp. and provides fundamental data on dietary needs for the critically endangered species, P. nobilis.

Genuine high-order interactions in brain networks and neurodegeneration

Brain functional networks have been traditionally studied considering only interactions between pairs of regions, neglecting the richer information encoded in higher orders of interactions. In consequence, most of the connectivity studies in neurodegeneration and dementia use standard pairwise metrics. Here, we developed a genuine high-order functional connectivity (HOFC) approach that captures interactions between 3 or more regions across spatiotemporal scales, delivering a more biologically plausible characterization of the pathophysiology of neurodegeneration. We applied HOFC to multimodal (electroencephalography [EEG], and functional magnetic resonance imaging [fMRI]) data from patients diagnosed with behavioral variant of frontotemporal dementia (bvFTD), Alzheimer's disease (AD), and healthy controls. HOFC revealed large effect sizes, which, in comparison to standard pairwise metrics, provided a more accurate and parsimonious characterization of neurodegeneration. The multimodal characterization of neurodegeneration revealed hypo and hyperconnectivity on medium to large-scale brain networks, with a larger contribution of the former. Regions as the amygdala, the insula, and frontal gyrus were associated with both effects, suggesting potential compensatory processes in hub regions. fMRI revealed hypoconnectivity in AD between regions of the default mode, salience, visual, and auditory networks, while in bvFTD between regions of the default mode, salience, and somatomotor networks. EEG revealed hypoconnectivity in the γ band between frontal, limbic, and sensory regions in AD, and in the δ band between frontal, temporal, parietal and posterior areas in bvFTD, suggesting additional pathophysiological processes that fMRI alone can not capture. Classification accuracy was comparable with standard biomarkers and robust against confounders such as sample size, age, education, and motor artifacts (from fMRI and EEG). We conclude that high-order interactions provide a detailed, EEG- and fMRI compatible, biologically plausible, and psychopathological-specific characterization of different neurodegenerative conditions.

Lombard Effect in Individuals With Nonphonotraumatic Vocal Hyperfunction: Impact on Acoustic, Aerodynamic, and Vocal Fold Vibratory Parameters

PURPOSE

This exploratory study aims to investigate variations in voice production in the presence of background noise (Lombard effect) in individuals with nonphonotraumatic vocal hyperfunction (NPVH) and individuals with typical voices using acoustic, aerodynamic, and vocal fold vibratory measures of phonatory function.

METHOD

Nineteen participants with NPVH and 19 participants with typical voices produced simple vocal tasks in three sequential background conditions: baseline (in quiet), Lombard (in noise), and recovery (5 min after removing the noise). The Lombard condition consisted of speech-shaped noise at 80 dB SPL through audiometric headphones. Acoustic measures from a microphone, glottal aerodynamic parameters estimated from the oral airflow measured with a circumferentially vented pneumotachograph mask, and vocal fold vibratory parameters from high-speed videoendoscopy were analyzed.

RESULTS

During the Lombard condition, both groups exhibited a decrease in open quotient and increases in sound pressure level, peak-to-peak glottal airflow, maximum flow declination rate, and subglottal pressure. During the recovery condition, the acoustic and aerodynamic measures of individuals with typical voices returned to those of the baseline condition; however, recovery measures for individuals with NPVH did not return to baseline values.

CONCLUSIONS

As expected, individuals with NPVH and participants with typical voices exhibited a Lombard effect in the presence of elevated background noise levels. During the recovery condition, individuals with NPVH did not return to their baseline state, pointing to a persistence of the Lombard effect after noise removal. This behavior could be related to disruptions in laryngeal motor control and may play a role in the etiology of NPVH.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.20415600.

Allostatic-Interoceptive Overload in Frontotemporal Dementia

BACKGROUND

The predictive coding theory of allostatic-interoceptive load states that brain networks mediating autonomic regulation and interoceptive-exteroceptive balance regulate the internal milieu to anticipate future needs and environmental demands. These functions seem to be distinctly compromised in behavioral variant frontotemporal dementia (bvFTD), including alterations of the allostatic-interoceptive network (AIN). Here, we hypothesize that bvFTD is typified by an allostatic-interoceptive overload.

METHODS

We assessed resting-state heartbeat evoked potential (rsHEP) modulation as well as its behavioral and multimodal neuroimaging correlates in patients with bvFTD relative to healthy control subjects and patients with Alzheimer's disease (N = 94). We measured 1) resting-state electroencephalography (to assess the rsHEP, prompted by visceral inputs and modulated by internal body sensing), 2) associations between rsHEP and its neural generators (source location), 3) cognitive disturbances (cognitive state, executive functions, facial emotion recognition), 4) brain atrophy, and 5) resting-state functional magnetic resonance imaging functional connectivity (AIN vs. control networks).

RESULTS

Relative to healthy control subjects and patients with Alzheimer's disease, patients with bvFTD presented more negative rsHEP amplitudes with sources in critical hubs of the AIN (insula, amygdala, somatosensory cortex, hippocampus, anterior cingulate cortex). This exacerbated rsHEP modulation selectively predicted the patients' cognitive profile (including cognitive decline, executive dysfunction, and emotional impairments). In addition, increased rsHEP modulation in bvFTD was associated with decreased brain volume and connectivity of the AIN. Machine learning results confirmed AIN specificity in predicting the bvFTD group.

CONCLUSIONS

Altogether, these results suggest that bvFTD may be characterized by an allostatic-interoceptive overload manifested in ongoing electrophysiological markers, brain atrophy, functional networks, and cognition.

Modelling neural entrainment and its persistence: influence of frequency of stimulation and phase at the stimulus offset

Neural entrainment, the synchronization of brain oscillations to the frequency of an external stimuli, is a key mechanism that shapes perceptual and cognitive processes.Objective.Using simulations, we investigated the dynamics of neural entrainment, particularly the period following the end of the stimulation, since the persistence (reverberation) of neural entrainment may condition future sensory representations based on predictions about stimulus rhythmicity.Methods.Neural entrainment was assessed using a modified Jansen-Rit neural mass model (NMM) of coupled cortical columns, in which the spectral features of the output resembled that of the electroencephalogram (EEG). We evaluated spectro-temporal features of entrainment as a function of the stimulation frequency, the resonant frequency of the neural populations comprising the NMM, and the coupling strength between cortical columns. Furthermore, we tested if the entrainment persistence depended on the phase of the EEG-like oscillation at the time the stimulus ended.Main Results.The entrainment of the column that received the stimulation was maximum when the frequency of the entrainer was within a narrow range around the resonant frequency of the column. When this occurred, entrainment persisted for several cycles after the stimulus terminated, and the propagation of the entrainment to other columns was facilitated. Propagation also depended on the resonant frequency of the second column, and the coupling strength between columns. The duration of the persistence of the entrainment depended on the phase of the neural oscillation at the time the entrainer terminated, such that falling phases (fromπ/2 to 3π/2 in a sine function) led to longer persistence than rising phases (from 0 toπ/2 and 3π/2 to 2π).Significance.The study bridges between models of neural oscillations and empirical electrophysiology, providing insights to the mechanisms underlying neural entrainment and the use of rhythmic sensory stimulation for neuroenhancement.

Dementia ConnEEGtome: Towards multicentric harmonization of EEG connectivity in neurodegeneration

The proposal to use brain connectivity as a biomarker for dementia phenotyping can be potentiated by conducting large-scale multicentric studies using high-density electroencephalography (hd- EEG). Nevertheless, several barriers preclude the development of a systematic "ConnEEGtome" in dementia research. Here we review critical sources of variability in EEG connectivity studies, and provide general guidelines for multicentric protocol harmonization. We describe how results can be impacted by the choice for data acquisition, and signal processing workflows. The implementation of a particular processing pipeline is conditional upon assumptions made by researchers about the nature of EEG. Due to these assumptions, EEG connectivity metrics are typically applicable to restricted scenarios, e.g., to a particular neurocognitive disorder. "Ground truths" for the choice of processing workflow and connectivity analysis are impractical. Consequently, efforts should be directed to harmonizing experimental procedures, data acquisition, and the first steps of the preprocessing pipeline. Conducting multiple analyses of the same data and a proper integration of the results need to be considered in additional processing steps. Furthermore, instead of using a single connectivity measure, using a composite metric combining different connectivity measures brings a powerful strategy to scale up the replicability of multicentric EEG connectivity studies. These composite metrics can boost the predictive strength of diagnostic tools for dementia. Moreover, the implementation of multi-feature machine learning classification systems that include EEG-based connectivity analyses may help to exploit the potential of multicentric studies combining clinical-cognitive, molecular, genetics, and neuroimaging data towards a multi-dimensional characterization of the dementia.

Assessing Testing Strategies and Duration of Quarantine in Contact Tracing for SARS-CoV-2: A Retrospective Study of San Francisco's COVID-19 Contact Tracing Program, June-August 2020

We sought to assess the proportion of elicited close contacts diagnosed with coronavirus disease 2019 at the start of and before exiting quarantine in San Francisco. From June 8 to August 31, 6946 contacts were identified: 3008 (46.3%) were tested, 940 (13.5%) tested positive, and 90% tested positive in the first 9 days of quarantine.

Vibrio mediterranei, a potential emerging pathogen of marine fauna: investigation of pathogenicity using a bacterial challenge in Pinna nobilis and development of a species-specific PCR

AIMS

Extreme mortality events affecting Pinna nobilis, some associated to Vibrio mediterranei, have depleted many populations of this bivalve. The objective of this study was to demonstrate pathogenicity of V. mediterranei in the host P. nobilis by performing a bacterial challenge in P. nobilis to understand if V. mediterranei has specific virulence in this host. To assist this objective, a secondary objective was to develop a species-specific DNA diagnostic test.

METHODS AND RESULTS

Pinna nobilis collected from local bays were used in a challenge experiment with V. mediterranei (strain IRTA18-108). The virulence in the host background of P. nobilis was demonstrated at doses of 10³ CFUs per animal. An alignment of published Vibrio sp. atpA sequences was used to design V. mediterranei-specific primers. Furthermore, data mining of published literature and V. mediterranei genomes identified multiple virulence-related genes (vir genes) from which specific primers were designed for PCR detection of selected genes.

CONCLUSION

Vibrio mediterranei strain IRTA18-108 is pathogenic in the host P. nobilis. The virulence genes sod, rtx and mshA were identified in this strain. Temperatures of 24°C or higher appear to trigger onset of virulence. Sensitivity and specificity of the Vm atpA PCR is useful for diagnosis of Vibriosis in shellfish.

SIGNIFICANCE AND IMPACT OF THE STUDY

The presence of previously described virulence genes have been confirmed in this strain. The specific Vm atpA PCR assay will aid management of future epizootics of this emerging pathogen of aquatic fauna, and improve surveillance capabilities for mortality events where Vibrios are suspect.

Improving EEG Muscle Artifact Removal With an EMG Array

Removal of artifacts induced by muscle activity is crucial for analysis of the electroencephalogram (EEG), and continues to be a challenge in experiments where the subject may speak, change facial expressions, or move. Ensemble empirical mode decomposition with canonical correlation analysis (EEMD-CCA) has been proven to be an efficient method for denoising of EEG contaminated with muscle artifacts. EEMD-CCA, likewise the majority of algorithms, does not incorporate any statistical information of the artifact, namely, electromyogram (EMG) recorded over the muscles actively contaminating the EEG. In this paper, we propose to extend EEMD-CCA in order to include an EMG array as information to aid the removal of artifacts, assessing the performance gain achieved when the number of EMG channels grow. By filtering adaptively (recursive least squares, EMG array as reference) each component resulting from CCA, we aim to ameliorate the distortion of brain signals induced by artifacts and denoising methods. We simulated several noise scenarios based on a linear contamination model, between real and synthetic EEG and EMG signals, and varied the number of EMG channels available to the filter. Our results exhibit a substantial improvement in the performance as the number of EMG electrodes increase from 2 to 16. Further increasing the number of EMG channels up to 128 did not have a significant impact on the performance. We conclude by recommending the use of EMG electrodes to filter components, as it is a computationally inexpensive enhancement that impacts significantly on performance using only a few electrodes.

Age and growth of the endangered fan mussel Pinna nobilis in the western Mediterranean Sea

The present work, which is the first comparative study of the growth of the fan mussel Pinna nobilis in the western Mediterranean, encompasses 12 populations of this species living in different environments in France and Spain. Two hundred nine shells were processed and used to obtain growth records from the posterior adductor muscle scar. Size-at-age data were fitted to the Von Bertalanffy growth model. Considerable variability in growth parameters and age was detected among the populations. The results show that the only two fan mussel populations remaining in Spain, which live in an estuary and a coastal lagoon, occupy habitats that are optimal for fast growth, but individuals show low longevity, complicating the long-term conservation of the species. Multivariate analyses groups the populations into three groups (SO, EO and LG), and a general model is proposed for each group; the model can be used as an approximation to calculate the ages of individuals living in similar environments.

P3353Safety and performance of stress testing: results from 78220 nuclear cardiology studies performed over 15 years in Brazil

Background

Stress testing for nuclear cardiology (NC) is safe for evaluating suspected or known coronary heart disease (CHD). Rates of serious adverse events (SAE) are low, roughly 1 death/myocardial infarction: 10,000 studies. However, this may vary depending on patient characteristics using different stress modalities.

Purpose

To describe the rates of SAE using different stress modalities in patients referred to NC.

Methods

We included all patients undergoing NC at Quanta in Curitiba, Brazil from 2003 to 2018. Stress modalities were categorized as: exercise (Ex), dipyridamole (Dip), a hybrid protocol of dypiridamole and low workload exercise (DipEx), and dobutamine (Dob). SAE during/after stress were recorded: cardiac arrest or ST segment elevation myocardial acute infarction (STEMI). Development of second or third degree atrial ventricular block (AVB) during stress and recovery were also recorded.

Results

From 78220 studies in 61984 patients (47% women, mean age 63 years-old), Ex was the most frequent stress modality (67%), followed by Dip (24%), DipEx (7%) and Dob (1,7%). Patients undergoing Ex were the youngest (mean age 60 vs 70 vs 65 vs 71 years old), the least likely of having hypertension (62 vs 78 vs 76 vs 75%) and diabetes (22 vs 35 vs 32 vs 32%) and had the lowest prevalence of known CHD (26 vs 35 vs 41 vs 30%, for Ex vs Dip vs DipEx vs Dob respectively, p<0.001 for all comparisons). Six patients had cardiac arrest and one STEMI, results in SAE rate of 1:11.144 studies. There was important differences among stress modalities, being higher for pharmacological stress, particularly DipEx (Table). This group had the highest prevalence of known CHD and higher baseline risk. AVB rates were higher when dipyridamole was used. All patients who arrested in the laboratory recovered with treatment.

Serious adverse events and stress in NC Adverse event Ex Dip DipEx Dob N=52,237 N=18,848 N=5,824 N=1,311 Cardiac Arrest or MI 1 : 17,412 1 : 9,424 1 : 2,912 None 2nd or 3rd Degree AVb 1 : 4,353 1 : 1,885 1 : 1,941 None Observe how adverse event rates different importantly in patients undergoing different stress modalities in NC.

Conclusion

In this large 15-year registry, rates of SAE related to stress testing in NC were low, albeit the SAE were much higher with pharmacological stress modalities, particularly with DipEx, which had the highest rate of patients with known CHD. Our findings suggest that the well-known 1:10,000 event rate does not necessarily apply to all stress modalities in NC. Physicians should take patient's baseline risk into account, particularly those requiring pharmacologic stress.

4223Income level and the prevalence of ischemic coronary heart disease in a low-mid-income country with high social inequalities. Influence of neighborhood walkability

Background

The greater burden of coronary heart disease (CHD) comes from low-middle income countries (LMIC). Socioeconomic status, environmental factors, poor access to healthcare, physical inactivity and excess consumption of carbohydrates, have explained part of this burden. However, the association between income level and CHD in LMIC with marked social inequalities is not fully understood, and whether there is influence of neighborhood walkability (walking-promoting potential of the residential built environment for daily activities) in this association requires further investigation.

Purpose

To investigate to what level income is associated with ischemic CHD in a LMIC with great social inequalities and to explore the potential role of neighborhood walkability in this association.

Methods

We evaluated patients referred for myocardial perfusion imaging with SPECT (SPECT-MPI) from February 2010 to August 2017 at a reference imaging center in our city, Brazil. Each patient was georeferenced and the exposure variable was the average income in Brazilian currency (Real) per month, from the patient's residential census block. Ischemic CHD was defined by an abnormal myocardial perfusion (summed stress score >3) during a SPECT-MPI study. Walkability was measured by a score combining street connectivity, residential density, commercial density and mixed land use. We used mixed effects models to evaluate the association between income level and ischemic CHD, adjusted for potential confounders, and performed a mediation analysis to measure the percentage of this association mediated by walkability.

Results

From 26,810 participants, those living in the lowest tertile income neighborhoods were younger (61±12 vs 63±13 vs 65±12 yrs old); with higher body mass index (28.4±5 vs 27.7±5 vs 27.4±4 kg/m2); more likely to be women (52 vs 49 vs 47%), current smokers (10 vs 9 vs 8%), sedentary (79 vs 76 vs 73%), having diabetes (27 vs 24 vs 23%), hypertension (65 vs 62 vs 60%) and with known CHD (21 vs 20 vs 19%) when compared to the second and the highest tertiles respectively, all with p<0.001. After adjusting for these potential confounders, income level was inversely associated with ischemic CAD (Figure). Neighborhoods with higher income levels were associated with better walkability scores (R = 0.34eta; p<0.001), but walkability did not mediate the association between income level and ischemic CHD (percent mediated = −0.3%).

Figure 1. Association of income and CHD

Conclusions

In this large registry from a LMIC population, living in a lower-income neighborhood was associated with higher prevalence of ischemic CHD. Even though neighborhood walkability was directly associated with neighborhood income, it did not explain the association between income level and ischemic CHD.

Neurophysiological Muscle Activation Scheme for Controlling Vocal Fold Models

A physiologically-based scheme that incorporates inherent neurological fluctuations in the activation of intrinsic laryngeal muscles into a lumped-element vocal fold model is proposed. Herein, muscles are activated through a combination of neural firing rate and recruitment of additional motor units, both of which have stochastic components. The mathematical framework and underlying physiological assumptions are described, and the effects of the fluctuations are tested via a parametric analysis using a body-cover model of the vocal folds for steady-state sustained vowels. The inherent muscle activation fluctuations have a bandwidth that varies with the firing rate, yielding both low and high-frequency components. When applying the proposed fluctuation scheme to the voice production model, changes in the dynamics of the system can be observed, ranging from fluctuations in the fundamental frequency to unstable behavior near bifurcation regions. The resulting coefficient of variation of the model parameters is not uniform with muscle activation. The stochastic components of muscle activation influence both the fine structure variability and the ability to achieve a target value for pitch control. These components can have a significant impact on the vocal fold parameters, as well as the outputs of the voice production model. Good agreement was found when contrasting the proposed scheme with prior experimental studies accounting for variability in vocal fold posturing and spectral characteristics of the muscle activation signal. The proposed scheme constitutes a novel and physiologically-based approach for controlling lumped-element models for normal voice production and can be extended to explore neuropathological conditions.

Connexinopathies: a structural and functional glimpse

Mutations in human connexin (Cx) genes have been related to diseases, which we termed connexinopathies. Such hereditary disorders include nonsyndromic or syndromic deafness (Cx26, Cx30), Charcot Marie Tooth disease (Cx32), occulodentodigital dysplasia and cardiopathies (Cx43), and cataracts (Cx46, Cx50). Despite the clinical phenotypes of connexinopathies have been well documented, their pathogenic molecular determinants remain elusive. The purpose of this work is to identify common/uncommon patterns in channels function among Cx mutations linked to human diseases. To this end, we compiled and discussed the effect of mutations associated to Cx26, Cx32, Cx43, and Cx50 over gap junction channels and hemichannels, highlighting the function of the structural channel domains in which mutations are located and their possible role affecting oligomerization, gating and perm/selectivity processes.

Changes of ocular aberrations with gaze

The dependence of the ocular aberrations on gaze has been studied in three eyes using a fast-acquisition, Hartmann-Shack wavefront sensor. Although there were some trends in the change of some aberration terms with gaze, the changes of most Zernike coefficients were smaller than their variability at each individual gaze position, due to the combined effects of microfluctuations of accommodation, eye movements, tear film dynamics, and measurement noise. For our particular experimental dataset, the confidence level at which the null hypothesis (i.e. that the aberrations do not change significantly with gaze) can be rejected is very low. Further advances in the study of the dependence of eye aberrations with gaze will require a tighter control of the sources of aberration variability at each individual gaze position.

The contribution of the fixational eye movements to the variability of the measured ocular aberration

The purpose of this work is to analyze the contribution of eye movements to the variability of the Zernike coefficients as determined with a Hartmann-Shack aberrometer. In order to isolate this effect we considered static aberrations tied to the eye pupil. We used several eye movements of different magnitude, both synthetic and corresponding to actual series recorded in our laboratory with different subjects. Our results show the relevance of the modal coupling induced by the estimation process and the benefit of correcting eye movements in order to get a better estimate of the ocular aberrations. They also show that eye movements during aberrometric measurements are an important source of apparent wavefront variability.

Regional lymphadenopathy in cat-scratch disease: ultrasonographic findings

BACKGROUND

Cat-scratch disease (CSD) is considered to be an emerging disease worldwide and is caused by Bartonella henselae, a gram-negative bacterium introduced by a scratch or bite of a cat. The most common clinical manifestation is regional lymphadenopathy, but clinical recognition may be difficult, as atypical manifestations may occur. The diagnosis is confirmed with serologic testing and histology is rarely needed. This paper is based on our experience with the use of ultrasonography in the diagnosis of CSD.

OBJECTIVE

The aim of this study was to describe the sonographic and color Doppler appearances of regional lymphadenopathy in CSD, as this has not widely reported in the literature.

MATERIALS AND METHODS

Forty-seven patients (average 9.4 years) were included who all had serologically and/or histologically proven CSD and had been studied using US early in the clinical course. All had a positive history of exposure to cats and exhibited regional lymphadenopathy.

RESULTS

US showed large hypoechoic adenopathy with some transmission enhancement and high vascularization on color-flow Doppler imaging. In 30 patients, abdominal US was also performed and splenic and/or hepatic granulomata were found in 10.

CONCLUSIONS

In our experience, sonography and especially color-Doppler and power-Doppler sonography was helpful in the diagnosis of CSD. We believe it should be used in the initial study of children with regional lymphadenopathy, and serologic testing should be performed when CSD is suspected.

[Bartonella henselae infection in immunocompetent patients: cat scratch disease]

BACKGROUND

Cat scratch disease, whose etiologic agent is Bartonella henselae, is a benign disease in immunocompetent subjects, characterized by lymphadenopathy of prolonged course and occasional involvement of other organs such as liver, spleen, central nervous system, eye and lung. In immunocompromised patients, the infection is bacteremic and disseminated.

AIM

To report Chilean cases of cat scratch disease.

PATIENTS AND METHODS

Ten children (seven male, aged between 6 and 13 years old) with histologically or serologically confirmed cat scratch disease are reported.

RESULTS

Lymphadenopathy location was pre auricular in four cases, axillary in two, inguinal in two and epitrochlear in two. Three children had fever over 39 degrees C and two had a parinaud syndrome. Nine children had a history of cat scratch and one of a cat byte. Six had an erythrocyte sedimentation rate over 40. Lymph node ultrasound examination was a useful diagnostic tool. Two patients had splenic granulomas. Lymph node biopsies were obtained in four cases, showing a suppurative granulomatous lymphadenitis in all and a positive Warthin-Starry stain in two. Serology, done in patients without histological confirmation was positive with titles ranging from 1:64 to 1:8192. All patients had a satisfactory outcome with regression of lymphadenopathy.

CONCLUSIONS

Infections by Bartonella hemselae occur in the Chilean population and must be considered in the differential diagnosis of regional lymph node enlargement.

[Neuroborreliosis in Chile. Report of a child probably infected by imported pets]

Lyme disease, caused by the spirochete Borrelia burgdorferi, has several clinical manifestations and is transmitted to man by tick bites. In Chile and Latin America, several cases have been reported, but none with immunoblot confirmation or isolation of the infecting organism. We report a 9 year old boy consulting with bilateral facial palsy, polyradiculoneuritis with tetraparesis and meningeal irritation. Cerebrospinal fluid analysis showed increased protein concentration without pleocytosis and negative viral or bacterial cultures. IgM antibodies against Borrelia burgdorferi, were positive by ELISA and were confirmed by immunoblot at the Reference Laboratory of the University of Connecticut. The child had a recent contact with hamsters brought from Germany. The substantiation of Lyme disease existence in Chile should prompt the search and isolation of the causal agent.

[Seroprevalence of Epstein Barr virus infection in a healthy population of Santiago de Chile]

To study the rate of infection by Epstein Barr virus (EBV) in Santiago, Chile, the prevalence of antibody to the viral capsid antigen (VCA-IgG) was determined in a group of 663 healthy individuals grouped by age and socioeconomic level (SEL). In addition, several risk factors for infection were studied. VCA-IgG was determined by ELISA. The total prevalence was 76.7%. When grouped by age and SEL, 50% of the children from low and medium SEL had been already infected by the age two, compared to 5.9% in the high SEL (p < 0.01). However, by age twenty, 90% of the total sample had already specific antibodies to EBV. Age and number of household members were positively associated with the infection. High socioeconomic level represented a delay factor in the acquisition of the virus, (p < 0.01). These results show that EBV infection is frequent in Santiago, occurring early in childhood among medium and low SEL. Hence, the classical infectious mononucleosis should be recognized more frequently among adolescents and young adults belonging to high SEL, while the clinical spectrum of associated manifestations different from the typical mononucleosis syndrome should be investigated among those exposed in early age.

Seroprevalence of Helicobacter pylori in Chile: vegetables may serve as one route of transmission

Helicobacter pylori infection is very common in Chilean adults, but the age-related prevalence, risk factors for infection, and mode of transmission in Chilean children are unknown. An ELISA was used to test for H. pylori antibodies in 1815 Chileans < 35 years of age. Seropositivity was > 60% in lower socioeconomic groups. H. pylori seropositivity correlated with increased age, low socioeconomic status, and consumption of uncooked vegetables by use of a logistic regression analysis. Risk factors that reached marginal significance were consumption of uncooked shell-fish, female sex, and residence in Santiago. Although multiple modes of transmission for H. pylori undoubtedly exist, prior studies have suggested that contamination of irrigation water by raw sewage (and the subsequent contamination of vegetables that are eaten uncooked) is a key factor in the transmission of enteric pathogens in Chile; H. pylori may be transmitted by a similar route.