scholarly journals Resonance modulation, annihilation and generation of antiresonance and antiphasonance in 3D neuronal systems: interplay of resonant and amplifying currents with slow dynamics

2016 ◽  
Author(s):  
Horacio G. Rotstein
Keyword(s):  
Linear Models ◽  
Three Dimensions ◽  
Input Frequency ◽  
Boundary Layer Problem ◽  
Impedance Profile ◽  
Response Amplification ◽  
Underlying Mechanisms ◽  
Neuronal Systems ◽  
Minimum Amplitude ◽  
Zero Phase

AbstractSubthreshold (membrane potential) resonance and phasonance (preferred amplitude and zero-phase responses to oscillatory inputs) in single neurons arise from the interaction between positive and negative feedback effects provided by relatively fast amplifying currents and slower resonant currents. In 2D neuronal systems, amplifying currents are required to be slaved to voltage (instantaneously fast) for these phenomena to occur. In higher dimensional systems, additional currents operating at various effective time scales may modulate and annihilate existing resonances and generate antiresonance (minimum amplitude response) and antiphasonance (zero-phase response with phase monotonic properties opposite to phasonance). We use mathematical modeling, numerical simulations and dynamical systems tools to investigate the mechanisms underlying these phenomena in 3D linear models, which are obtained as the linearization of biophysical (conductance-based) models. We characterize the parameter regimes for which the system exhibits the various types of behavior mentioned above in the rather general case in which the underlying 2D system exhibits resonance. We consider two cases: (i) the interplay of two resonant gating variables, and (ii) the interplay of one resonant and one amplifying gating variables. Increasing levels of an amplifying current cause (i) a response amplification if the amplifying current is faster than the resonant current, (ii) resonance and phasonance attenuation and annihilation if the amplifying and resonant currents have identical dynamics, and (iii) antiresonance and antiphasonance if the amplifying current is slower than the resonant current. We investigate the underlying mechanisms by extending the envelope-plane diagram approach developed in previous work (for 2D systems) to three dimensions to include the additional gating variable, and constructing the corresponding envelope curves in these envelope-space diagrams. We find that antiresonance and antiphasonance emerge as the result of an asymptotic boundary layer problem in the frequency domain created by the different balances between the intrinsic time constants of the cell and the input frequency f as it changes. For large enough values of f the envelope curves are quasi-2D and the impedance profile decrease with the input frequency. In contrast, for f ≪ 1 the dynamics is quasi-1D and the impedance profile increases above the limiting value in the other regime. Antiresonance is created because the continuity of the solution requires the impedance profile to connect the portions belonging to the two regimes. If in doing so the phase profile crosses the zero value, then antiphasonance is also generated.

scholarly journals A New Look at Cohort Trend and Underlying Mechanisms in Cognitive Functioning

2020 ◽  
Author(s):  
Hui Zheng
Keyword(s):  
Cognitive Functioning ◽  
Baby Boomers ◽  
Linear Models ◽  
The United States ◽  
Household Wealth ◽  
Summary Score ◽  
Birth Cohorts ◽  
Explanatory Variables ◽  
Greatest Generation ◽  
Underlying Mechanisms

Abstract Objectives The prevalence of dementia in the United States seems to have declined over the last few decades. We investigate trends and their underlying mechanisms in cognitive functioning (CF) across 7 decades of birth cohorts from the Greatest Generation to Baby Boomers. Methods Data come from 30,191 participants of the 1996–2014 Health and Retirement Study. CF is measured as a summary score on a 35-point cognitive battery of items. We use generalized linear models to examine the trends in CF and explanatory variables across birth cohorts. Then, Karlson–Holm–Breen decomposition method is used to evaluate the contribution of each explanatory variable to the trend of CF. Results CF has been improving from the Greatest Generation to Late Children of Depression and War Babies, but then significantly declines since the Early-Baby Boomers and continues into Mid-Baby Boomers. This pattern is observed universally across genders, race/ethnicities, education groups, occupations, income, and wealth quartiles. The worsening CF among Baby Boomers does not originate from childhood conditions, adult education, or occupation. It can be attributed to lower household wealth, lower likelihood of marriage, higher levels of loneliness, depression and psychiatric problems, and more cardiovascular risk factors (e.g., obesity, physical inactivity, hypertension, stroke, diabetes, and heart disease). Discussion The worsening CF among Baby Boomers may potentially reverse past favorable trends in dementia as they reach older ages and cognitive impairment becomes more common if no effective interventions and policy responses are in place.

scholarly journals A novel framework for classification of selection processes in epidemiological research

2020 ◽  
Author(s):  
Jonas Bjork ◽  
Anton Nilsson ◽  
Carl Bonander ◽  
Ulf Strömberg
Keyword(s):  
Research Question ◽  
Population Level ◽  
Three Dimensions ◽  
Observational Research ◽  
Population Composition ◽  
Epidemiological Research ◽  
Selection Processes ◽  
Underlying Mechanisms ◽  
Case Basis

Abstract Background: Selection and selection bias are terms that lack consistent definitions and have varying meaning and usage across disciplines. There is also confusion in current definitions between underlying mechanisms that lead to selection and their consequences. Consequences of selection on study validity must be judged on a case-by-case basis depending on research question, study design and analytical decisions. The overall aim of the study was to develop a simple but general framework for classifying various types of selection processes of relevance for epidemiological research. Methods: Several original articles from the epidemiological literature and from related areas of observational research were reviewed in search of examples of selection processes, used terminology and description of the underlying mechanisms. Results: We classified the identified selection processes in three dimensions: i) selection level (selection at the population level vs. study-specific selection), ii) type of mechanism (selection in exposure vs. selection in population composition), iii) timing of the selection (at exposure entry, during exposure or post-outcome). Conclusions: Increased understanding of when, how, and why selection occur is an important step towards improved validity of epidemiological research.

Feedforward Tracking Controller Design Based on the Identification of Low Frequency Dynamics

1993 ◽  
Vol 115 (3) ◽  
pp. 348-356 ◽  
Author(s):  
E. D. Tung ◽  
M. Tomizuka
Keyword(s):  
High Speed ◽  
Linear Models ◽  
Controller Design ◽  
Phase Error ◽  
Low Frequency ◽  
Reference Trajectory ◽  
Accurate Identification ◽  
Tracking Controller ◽  
Feed Drive System ◽  
Zero Phase

Several methodologies are proposed for identifying the dynamics of a machine tool feed drive system in the low frequency region. An accurate identification is necessary for the design of a feedforward tracking controller, which achieves unity gain and zero phase shift for the overall system in the relevant frequency band. In machine tools and other mechanical systems, the spectrum of the reference trajectory is composed of low frequency signals. Standard least squares fits are shown to heavily penalize high frequency misfit. Linear models described by the output-error (OE) and Autoregressive Moving Average with eXogenous Input (ARMAX) models display better closeness-of-fit properties at low frequency. Based on the identification, a feedforward compensator is designed using the Zero Phase Error Tracking Controller (ZPETC). The feedforward compensator is experimentally shown to achieve near-perfect tracking and contouring of high-speed trajectories on a machining center X-Y bed.

scholarly journals Geographic Variation in the Petiole–Lamina Relationship of 325 Eastern Qinghai–Tibetan Woody Species: Analysis in Three Dimensions

2021 ◽  
Vol 12 ◽  
Author(s):  
Yanan Li ◽  
Xiaomei Kang ◽  
Jieyang Zhou ◽  
Zhigang Zhao ◽  
Shiting Zhang ◽  
...  
Keyword(s):  
Environmental Gradients ◽  
Meta Analysis ◽  
Woody Species ◽  
Light Interception ◽  
Three Dimensions ◽  
Cross Sectional ◽  
Drag Forces ◽  
Species Analysis ◽  
Underlying Mechanisms ◽  
Relationship Of

The petiole–lamina relationship is central to the functional tradeoff between photosynthetic efficiency and the support/protection cost. Understanding environmental gradients in the relationship and its underlying mechanisms remains a critical challenge for ecologists. We investigated the possible scaling of the petiole–lamina relationships in three dimensions, i.e., petiole length (PL) vs. lamina length (LL), petiole cross sectional area (PCA) vs. lamina area (LA), and petiole mass (PM) vs. lamina mass (LM), for 325 Qinghai–Tibetan woody species, and examined their relation to leaf form, altitude, climate, and vegetation types. Both crossspecies analysis and meta-analysis showed significantly isometric, negatively allometric, and positively allometric scaling of the petiole–lamina relationships in the length, area, and mass dimensions, respectively, reflecting an equal, slower, and faster variation in the petiole than in the lamina in these trait dimensions. Along altitudinal gradients, the effect size of the petiole–lamina relationship decreased in the length and mass dimensions but increased in the area dimension, suggesting the importance of enhancing leaf light-interception and nutrient transport efficiency in the warm zones in petiole development, but enhancing leaf support/protection in the cold zones. The significant additional influences of LA, LM, and LA were observed on the PL–LL, PCA–LA, and PM–LM relationships, respectively, implying that the single-dimension petiole trait is affected simultaneously by multidimensional lamina traits. Relative to simple-leaved species, the presence of petiolule in compound-leaved species can increase both leaf light interception and static gravity loads or dynamic drag forces on the petiole, leading to lower dependence of PL variation on LL variation, but higher biomass allocation to the petiole. Our study highlights the need for multidimension analyses of the petiole–lamina relationships and illustrates the importance of plant functional tradeoffs and the change in the tradeoffs along environmental gradients in determining the relationships.

Abstract P202: Non-targeted Metabolomics Study Identify Multiple Metabolites Associated With Body Mass Index

Circulation ◽  
2018 ◽  
Vol 137 (suppl_1) ◽  
Author(s):  
Shengxu Li ◽  
Changwei Li ◽  
Tanika N Kelly ◽  
Xiaoying Gu ◽  
Xiao Sun ◽  
...  
Keyword(s):  
Body Mass Index ◽  
Body Mass ◽  
Linear Models ◽  
Control Measures ◽  
Health Consequences ◽  
Targeted Metabolomics ◽  
Heart Study ◽  
Metabolomics Study ◽  
Blacks And Whites ◽  
Underlying Mechanisms

Background: Non-targeted metabolomics technology provides a powerful tool to examine the complex etiology of obesity and the underlying mechanisms for its health consequences. The current study aimed to examine the associations of metabolites, quantified by non-targeted metabolomics technology, with body mass index (BMI) in the Bogalusa Heart Study. Methods: The study included 1,261 participants (825 White and 436 Blacks) aged 34-58 years. General linear models were used to examine the associations of BMI with the 1,202 metabolites that passed rigorous quality control measures, adjusted for age, sex, smoking, drinking, education, and total physical activity in Blacks and Whites, separately. Weighted correlation network analysis (WGCNA) was used to build metabolites modules according to pair-wise correlations (signed positive correlation and unsigned correlation regardless of correlation direction) among all metabolites; partial correlation was used to assess the link between each module and BMI. Results: Six-eight metabolites showed Bonferroni-corrected (P < 4.16E-5) associations with BMI in both Blacks and Whites. The most significant metabolite was glutamate (P = 1.52E-12 in Blacks and P = 1.47E-37 in Whites). Among the 46 significant metabolites with known identities, a majority were involved in pathways of lipids (22 metabolites) and amino acids (13 metabolites). Fifteen unsigned metabolites modules were identified and six of the modules showed significant correlation with BMI (absolute r = 0.11-0.14); ten signed metabolites modules were identified and five of them were significantly correlated with BMI (absolute r = 0.14-0.31). Conclusion: We have identified multiple metabolites robustly associated with BMI, which have novel biological implications for obesity and its health consequences.

Electrophysiology and Behavior of Cnidarian Nervous Systems

2019 ◽  
Author(s):  
Robert W. Meech
Keyword(s):  
Nervous System ◽  
Hierarchical Control ◽  
Primary Objective ◽  
Comparative Approach ◽  
Individual Species ◽  
Sea Anemones ◽  
Wide Range ◽  
Electrophysiological Studies ◽  
Underlying Mechanisms ◽  
Neuronal Systems

Although the Cnidaria have evolved a wide range of body forms matched with an equally varied neural anatomy, individual species exhibit common patterns of behavior. For example, in all species a key challenge for the nervous system is to transfer food from the peripherally mounted tentacles to the centrally located stomach. Foraging movements, necessary to maintain the food supply, must be accomplished in such a way as to avoid interference with the primary objective of getting prey into the mouth. Furthermore, the hunt for prey must be balanced by a measured response to “threat.” Different species respond to threat in markedly different ways, but in each case foraging is inhibited, just as it is during transmission of food. One hundred years ago, G. H. Parker questioned whether a centralized or a locally organized nervous system could best account for sea anemone behavior. Anatomical and electrophysiological studies now suggest that in most Cnidaria there is a degree of hierarchical control, with local reflexes coordinated by more condensed systems of neurons. This organization is highly developed in the nerve rings of hydrozoan medusae and takes the form of ganglion-like rhopalia in the Cubozoa. Even in hydrozoan polyps such as Hydra there are at least four separate neuronal systems. It is likely that the underlying mechanisms (containing both homologous and analogous elements) will be best revealed by a comparative approach that directly relates behavior with its molecular basis. Useful examples include comparisons between sea anemones with and without through-conducting systems; between hydra with and without oral rings; between medusae with and without coordinated escape swimming. Recent advances in transgenomic labeling have shown the way forward.

scholarly journals Contractile and chiral activities codetermine the helicity of swimming droplet trajectories

2017 ◽  
Vol 114 (18) ◽  
pp. 4631-4636 ◽  
Author(s):  
Elsen Tjhung ◽  
Michael E. Cates ◽  
Davide Marenduzzo
Keyword(s):  
Computer Simulation ◽  
Biological Systems ◽  
Local Scale ◽  
Three Dimensions ◽  
Nonequilibrium Systems ◽  
Active Fluid ◽  
Run And Tumble ◽  
Underlying Mechanisms

Active fluids are a class of nonequilibrium systems where energy is injected into the system continuously by the constituent particles themselves. Many examples, such as bacterial suspensions and actomyosin networks, are intrinsically chiral at a local scale, so that their activity involves torque dipoles alongside the force dipoles usually considered. Although many aspects of active fluids have been studied, the effects of chirality on them are much less known. Here, we study by computer simulation the dynamics of an unstructured droplet of chiral active fluid in three dimensions. Our model considers only the simplest possible combination of chiral and achiral active stresses, yet this leads to an unprecedented range of complex motilities, including oscillatory swimming, helical swimming, and run-and-tumble motion. Strikingly, whereas the chirality of helical swimming is the same as the microscopic chirality of torque dipoles in one regime, the two are opposite in another. Some of the features of these motility modes resemble those of some single-celled protozoa, suggesting that underlying mechanisms may be shared by some biological systems and synthetic active droplets.

Evolution and ontogeny of neural circuits

1984 ◽  
Vol 7 (3) ◽  
pp. 321-331 ◽  
Author(s):  
Sven O. E. Ebbesson
Keyword(s):  
Broad Spectrum ◽  
Neural Circuits ◽  
Ontogenetic Development ◽  
Similar Process ◽  
Neural Pathways ◽  
Interspecific Variability ◽  
Primitive Condition ◽  
Underlying Mechanisms ◽  
Neural Evolution ◽  
Neuronal Systems

AbstractRecent studies on neural pathways in a broad spectrum of vertebrates suggest that, in addition to migration and an increase in the number of certain select neurons, a significant aspect of neural evolution is a “parcellation” (segregation-isolation) process that involves the loss of selected connections by the new aggregates. A similar process occurs during ontogenetic development. These findings suggest that in many neuronal systems axons do not invade unknown territories during evolutionary or ontogenetic development but follow in their ancestors' paths to their ancestral targets; if the connection is later lost, it reflects the specialization of the circuitry.The pattern of interspecific variability suggests (1) that overlap of circuits is a more common feature in primitive (generalized) than in specialized brain organizations and (2) that most projections, such as the retinal, thalamotelencephalic, corticotectal, and tectal efferent ones, were bilateral in the primitive condition. Specialization of these systems in some vertebrate groups has involved the selective loss of connections, resulting in greater isolation of functions. The parcellation process may also play an important role in cell diversification.The parcellation process as described here is thought to be one of several underlying mechanisms of evolutionary and ontogenetic differentiation.

scholarly journals Neuronal resonance can be generated independently at distinct levels of organization

2020 ◽  
Author(s):  
Eran Stark ◽  
Horacio G. Rotstein
Keyword(s):  
Complex Phenomenon ◽  
Input Frequency ◽  
Biophysical Modeling ◽  
Extracellular Recordings ◽  
Levels Of Organization ◽  
Periodic Input ◽  
Subthreshold Resonance ◽  
Low Pass ◽  
Neuronal Systems ◽  
High Pass

ABSTRACTNeuronal resonance is defined as maximal amplification of the response of a system to a periodic input at a finite non-zero input frequency band. Resonance has been observed experimentally in the nervous system at the level of membrane potentials, spike times, post-synaptic potentials, and neuronal networks. It is often assumed that resonance at one level of organization endows resonance at another level, but how the various forms of neuronal resonances interact is unknown. Here we show that a direct link of the frequency response properties across neuronal levels of organization is not necessary. Using detailed biophysical modeling combined with numerical simulations, extracellular recordings, and optogenetic manipulations from behaving mice, we show how low-pass filtering, high-pass filtering, and amplification mechanisms can generate resonance at a single level of organization. Subthreshold resonance, synaptic resonance, and spiking resonance can each occur in the lack of resonance at any other level of organization. In contrast, frequencydependent mechanisms at several levels of organization are required to generate the more complex phenomenon of network resonance. Together, these results show that multiple independent mechanisms can generate resonance in neuronal systems.

scholarly journals A novel framework for classification of selection processes in epidemiological research

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Jonas Björk ◽  
Anton Nilsson ◽  
Carl Bonander ◽  
Ulf Strömberg
Keyword(s):  
Research Question ◽  
Population Level ◽  
Three Dimensions ◽  
Observational Research ◽  
Epidemiological Research ◽  
Selection Processes ◽  
Underlying Mechanisms ◽  
Case Basis

Abstract Background Selection and selection bias are terms that lack consistent definitions and have varying meaning and usage across disciplines. There is also confusion in current definitions between underlying mechanisms that lead to selection and their consequences. Consequences of selection on study validity must be judged on a case-by-case basis depending on research question, study design and analytical decisions. The overall aim of the study was to develop a simple but general framework for classifying various types of selection processes of relevance for epidemiological research. Methods Several original articles from the epidemiological literature and from related areas of observational research were reviewed in search of examples of selection processes, used terminology and description of the underlying mechanisms. Results We classified the identified selection processes in three dimensions: i) selection level (selection at the population level vs. study-specific selection), ii) type of mechanism (selection in exposure vs. selection in population composition), iii) timing of the selection (at exposure entry, during exposure/follow-up or post-outcome). Conclusions Increased understanding of when, how, and why selection occur is an important step towards improved validity of epidemiological research.

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