Estimating null and potent modes of feedforward communication in a computational model of cortical activity

Communication across anatomical areas of the brain is key to both sensory and motor processes. Dimensionality reduction approaches have shown that the covariation of activity across cortical areas follows well-delimited patterns. Some of these patterns fall within the "potent space" of neural interactions and generate downstream responses; other patterns fall within the "null space" and prevent the feedforward propagation of synaptic inputs. Despite growing evidence for the role of null space activity in visual processing as well as preparatory motor control, a mechanistic understanding of its neural origins is lacking. Here, we developed a mean-rate model that allowed for the systematic control of feedforward propagation by potent and null modes of interaction. In this model, altering the number of null modes led to no systematic changes in firing rates, pairwise correlations, or mean synaptic strengths across areas, making it difficult to characterize feedforward communication with common measures of functional connectivity. A novel measure termed the null ratio captured the proportion of null modes relayed from one area to another. Applied to simultaneous recordings of primate cortical areas V1 and V2 during image viewing, the null ratio revealed that feedforward interactions have a broad null space that may reflect properties of visual stimuli.

The heritability of BMI varies across the range of BMI: a heritability curve analysis in a twin cohort

The heritability of traits such as body mass index (BMI), a measure of obesity, is generally estimated using family, twin, and increasingly by molecular genetic approaches. These studies generally assume that genetic effects are uniform across all trait values, yet there is emerging evidence that this may not always be the case. This paper analyzes twin data using a recently developed measure of heritability called the heritability curve. Under the assumption that trait values in twin pairs are governed by a flexible Gaussian mixture distribution, heritability curves may vary across trait values. The data consist of repeated measures of BMI on 1506 monozygotic (MZ) and 2843 like-sexed dizygotic (DZ) adult twin pairs, gathered from multiple surveys in older Finnish Twin Cohorts. The heritability curve and BMI value-specific MZ and DZ pairwise correlations were estimated, and these varied across the range of BMI. MZ correlations were highest at BMI values from 21 to 24, with a stronger decrease for women than for men at higher values. Models with additive and dominance effects fit best at low and high BMI values, while models with additive genetic and common environmental effects fit best in the normal range of BMI. Thus, we demonstrate that twin and molecular genetic studies need to consider how genetic effects vary across trait values. Such variation may reconcile findings of traits with high heritabilities and major differences in mean values between countries or over time.

Context-dependent relationships between locus coeruleus firing patterns and coordinated neural activity in the anterior cingulate cortex

Ascending neuromodulatory projections from the locus coeruleus (LC) affect cortical neural networks via the release of norepinephrine (NE). However, the exact nature of these neuromodulatory effects on neural activity patterns in vivo is not well understood. Here we show that in awake monkeys, LC activation is associated with changes in coordinated activity patterns in the anterior cingulate cortex (ACC). These relationships, which are largely independent of changes in firing rates of individual ACC neurons, depend on the type of LC activation: ACC pairwise correlations tend to be reduced when ongoing (baseline) LC activity increases but enhanced when external events evoke transient LC responses. Both relationships covary with pupil changes that reflect LC activation and arousal. These results suggest that modulations of information processing that reflect changes in coordinated activity patterns in cortical networks can result partly from ongoing, context-dependent, arousal-related changes in activation of the LC-NE system.

Fireworks—a source of nanoparticles, PM2.5, PM10, and carbonaceous aerosols

Fireworks pollute the local atmosphere with various air pollutants, which can pose a health hazard for the local population. Mass and number concentrations of aerosols were measured before, during, and after the 2016/2017 New Year event in Ljubljana, Slovenia. Our findings highlight the negative impact of fireworks on the environment. First, both the mass concentration of black carbon and the number of concentrations of nanoparticles between 80 and 150 nm increased shortly after midnight. Second, on Jan 1, 2017, there was an increase in the average daily mass concentrations of PM10 and PM2.5. Third, on this day, our devices also detected increased air pollution by Al, Ba, Sr, and Cu, that is, heavy metals usually associated with fireworks. Their Jan 1 mass concentrations were more than 10 times (and Sr more than 140 times) higher than their average daily mass concentrations from Jan 3 (when their mass concentrations returned to more normal levels) to Jan 31. We also found that pairwise correlations between nanoparticles, PM10, and black carbon are positive, strong, and statistically significant. Besides carbon, the chemical analysis of the collected particles revealed the presence of typical elements used in pyrotechnic devices and their significant positive correlation.

A Generative Model for Correlated Graph Signals

A graph signal is a random vector with a partially known statistical description. The observations are usually sufficient to determine marginal distributions of graph node variables and their pairwise correlations representing the graph edges. However, the curse of dimensionality often prevents estimating a full joint distribution of all variables from the available observations. This paper introduces a computationally effective generative model to sample from arbitrary but known marginal distributions with defined pairwise correlations. Numerical experiments show that the proposed generative model is generally accurate for correlation coefficients with magnitudes up to about 0.3, whilst larger correlations can be obtained at the cost of distribution approximation accuracy. The generative models of graph signals can also be used to sample multivariate distributions for which closed-form mathematical expressions are not known or are too complex.

Relationship between diffraction peak, network topology, and amorphous-forming ability in silicon and silica

The network topology in disordered materials is an important structural descriptor for understanding the nature of disorder that is usually hidden in pairwise correlations. Here, we compare the covalent network topology of liquid and solidified silicon (Si) with that of silica (SiO2) on the basis of the analyses of the ring size and cavity distributions and tetrahedral order. We discover that the ring size distributions in amorphous (a)-Si are narrower and the cavity volume ratio is smaller than those in a-SiO2, which is a signature of poor amorphous-forming ability in a-Si. Moreover, a significant difference is found between the liquid topology of Si and that of SiO2. These topological features, which are reflected in diffraction patterns, explain why silica is an amorphous former, whereas it is impossible to prepare bulk a-Si. We conclude that the tetrahedral corner-sharing network of AX2, in which A is a fourfold cation and X is a twofold anion, as indicated by the first sharp diffraction peak, is an important motif for the amorphous-forming ability that can rule out a-Si as an amorphous former. This concept is consistent with the fact that an elemental material cannot form a bulk amorphous phase using melt quenching technique.

Age and sex dependent changes of free circulating blood metabolite and lipid abundances, correlations and ratios

In this study we investigated how the concentrations, pairwise correlations, and ratios of 202 free circulating blood metabolites and lipids vary with age in a panel of n=1882 subjects ranging from 48 to 94 years. We report a statistically significant sex-dependent association with age of a panel of metabolites and lipids involving, in women cohort, linoleic acid, α-linoleic acid, and carnitine, and, in men sub-group, monoacylglycerols and lysophosphatidylcholines. Evaluating the association of correlations among metabolites and/or lipids with age, we found that phosphatidylcholines correlations tend to have a positive trend associated with age in women, and monoacylglycerols and lysophosphatidylcholines correlations tend to have a negative trend associated with age in men. The association of ratio between molecular features with age reveals that the ratio between decanoyl L-carnitine and lysophosphatidylcholine in women have a negative association with age, while the ratios between L-carnitine, L-acetylcarnitine, and phosphatidylcholines in men have a positive association with age. These results suggest an age-dependent remodeling of lipid metabolism that induces changes in cell membrane bilayer composition and cell cycle mechanisms. Furthermore, we conclude that lipidome is directly involved in this age-dependent differentiation. Our results demonstrate that, using a comprehensive approach to aging focused on the changes of concentrations and relationships thereof, as expressed by their correlations and ratios, it is possible to obtain relevant information about metabolic dynamics associated with age.

Comprehensive approach to the tuberculosis indicators assessment of the children population in the Republic of Crimea

Introduction. Childhood tuberculosis (TB) control is relevant due to the peculiarities of its course in this age group, and the TB incidence in children is an important prognostic epidemiological indicator.Aim. Use of multivariate statistical analysis to estimate and predict childhood TB indicators in the Republic of Crimea (RC).Materials and methods. The official TB statistics in the Republic of Crimea for 2014-2018 are used. The calculated means of the indicators are checked for normality using the Kolmogorov-Smirnov and Shapiro-Wilk tests. Pearson correlation analysis is applied to determine pair correlation relationships. Stepwise multiple regression analysis is carried out to determine group conditionality of the indicators, where coefficients, with which significant pairwise correlations are found, are selected as independent variables. Based on the results, multiple regression equations are made to predict the values of dependent variables. The data is processed using Statistica 10.0 software.Results. For childhood TB incidence, strong direct correlations are established with the incidence and prevalence of pulmonary TB among children. The paired correlation coefficient between the incidence of childhood TB and childhood lung TB and the detection of active TB patients in preventive examinations of children varied in the range of 0.63-0.72. For the prevalence of TB among children, strong direct correlations were found with the incidence of TB and pulmonary TB in children. Multiple correlation coefficients for the incidence and prevalence of childhood TB exceeded the values of paired correlation coefficients and were in the range of 0.93 to 0.98 (p<0.001), indicating greater significance of group conditionality of the indicators. Determination coefficients R2 were between 0.87 and 0.96. Multiple regression models were built for the childhood TB incidence, childhood lung TB incidence, childhood TB prevalence, childhood lung TB prevalence.Conclusion. The found strong direct pairwise correlations for childhood TB incidence and prevalence and childhood pulmonary TB incidence and prevalence can serve as prognostic criteria and reflect the quality of antituberculosis interventions. High values of paired correlation coefficient between childhood TB incidence and childhood pulmonary TB and detection of patients with active TB in preventive examinations of children are a criterion of quality of both TB services and primary care, which can prevent the spread of TB and improve the epidemic situation of TB in Crimea. The calculated multiple regression models for the studied indicators can serve the needs of practical forecasting in Healthcare.

Pricing insurance policies with offsetting relationship

This paper investigates the benefits of incorporating diversification effects into the pricing process of insurance policies from two different business lines. The paper shows that, for the same risk reduction, insurers pricing policies jointly can have a competitive advantage over those pricing them separately. However, the choice of competitiveness constrains the underwriting flexibility of joint pricers. The paper goes a step further by modelling explicitly the relationship between premiums and the number of customers in each line. Using the total collected premiums as a criterion to compare the competing strategies, the paper provides conditions for the optimal pricing decision based on policyholders’ sensitivity to price discounts. The results are illustrated for a portfolio of annuities and assurances. Further, using non-life data from the Brazilian insurance market, an empirical exploration shows that most pairs satisfy the condition for being priced jointly, even when pairwise correlations are high.

Transformation of Primary Sensory Cortical Representations from Layer 4 to Layer 2

Sensory input arrives from thalamus in cortical layer (L) 4, from which it flows predominantly to superficial layers, so that L4 to L2 constitutes one of the earliest cortical feedforward networks. Despite extensive study, the transformation performed by this network remains poorly understood. We use two-photon calcium imaging in L2-4 of primary vibrissal somatosensory cortex (vS1) to record neural activity as mice perform an object localization task with two whiskers. We find that touch responses sparsen but become more reliable from L4 to L2, with superficial neurons responding to a broader range of touches. Decoding of sensory features either improves from L4 to L2 or remains unchanged. Pairwise correlations increase superficially, with L2/3 containing ensembles of mostly broadly tuned neurons responding robustly to touch. Thus, from L4 to L2, cortex transitions from a dense probabilistic code to a sparse and robust ensemble-based code that improves stimulus decoding, facilitating perception.