scholarly journals Robust emergence of sharply tuned place cell responses in hippocampal neurons with structural and biophysical heterogeneities

2019 ◽  
Author(s):  
Reshma Basak ◽  
Rishikesh Narayanan
Keyword(s):  
Hippocampal Neurons ◽  
Degrees Of Freedom ◽  
Pyramidal Neurons ◽  
Place Field ◽  
Synaptic Localization ◽  
Sharp Feature ◽  
Channel Expression ◽  
Dendritic Spike ◽  
Spike Initiation ◽  
The Impact

ABSTRACTHippocampal pyramidal neurons sustain propagation of fast electrical signals and are electrotonically non-compact structures exhibiting cell-to-cell variability in their complex dendritic arborization. In this study, we demonstrate that sharp place-field tuning and several somato-dendritic functional maps concomitantly emerge despite the presence of geometrical heterogeneities in these neurons. We establish this employing an unbiased stochastic search strategy involving thousands of models that spanned several morphologies and distinct profiles of dispersed synaptic localization and channel expression. Mechanistically, employing virtual knockout models, we explored the impact of bidirectional modulation in dendritic spike prevalence on place-field tuning sharpness. Consistent with prior literature, we found that across all morphologies, virtual knockout of either dendritic fast sodium channels or N-methyl-D-aspartate receptors led to a reduction in dendritic spike prevalence, whereas A-type potassium channel knockouts resulted in a nonspecific increase in dendritic spike prevalence. However, place-field tuning sharpness was critically impaired in all three sets of virtual knockout models, demonstrating that sharpness in feature tuning is maintained by an intricate balance between mechanisms that promote and those that prevent dendritic spike initiation. From the functional standpoint of the emergence of sharp feature tuning and intrinsic functional maps, within this framework, geometric variability was compensated by a combination of synaptic democracy, the ability of randomly dispersed synapses to yield sharp tuning through dendritic spike initiation, and ion-channel degeneracy. Our results suggest electrotonically non-compact neurons to be endowed with several degrees of freedom, encompassing channel expression, synaptic localization and morphological micro-structure, in achieving sharp feature encoding and excitability homeostasis.

Optical detection of dendritic spike initiation in hippocampal CA1 pyramidal neurons

Neuroscience ◽  
2003 ◽  
Vol 118 (4) ◽  
pp. 899-907 ◽  
Author(s):  
A Kasuga ◽  
R Enoki ◽  
Y Hashimoto ◽  
H Akiyama ◽  
Y Kawamura ◽  
...  
Keyword(s):  
Pyramidal Neurons ◽  
Optical Detection ◽  
Ca1 Pyramidal Neurons ◽  
Hippocampal Ca1 ◽  
Dendritic Spike ◽  
Spike Initiation

Mechanically-Tunable Quantum Interference in Ferrocene-Based Single-Molecule Junctions

2020 ◽  
Author(s):  
María Camarasa-Gómez ◽  
Daniel Hernangómez-Pérez ◽  
Michael S. Inkpen ◽  
Giacomo Lovat ◽  
E-Dean Fung ◽  
...  
Keyword(s):  
Single Molecule ◽  
Quantum Interference ◽  
Degrees Of Freedom ◽  
Building Blocks ◽  
Ferrocene Derivative ◽  
Single Molecule Junctions ◽  
Molecule Junction ◽  
Single Molecule Junction ◽  
The Impact ◽  
D Orbitals

Ferrocenes are ubiquitous organometallic building blocks that comprise a Fe atom sandwiched between two cyclopentadienyl (Cp) rings that rotate freely at room temperature. Of widespread interest in fundamental studies and real-world applications, they have also attracted<br>some interest as functional elements of molecular-scale devices. Here we investigate the impact of<br>the configurational degrees of freedom of a ferrocene derivative on its single-molecule junction<br>conductance. Measurements indicate that the conductance of the ferrocene derivative, which is<br>suppressed by two orders of magnitude as compared to a fully conjugated analog, can be modulated<br>by altering the junction configuration. Ab initio transport calculations show that the low conductance is a consequence of destructive quantum interference effects that arise from the hybridization of metal-based d-orbitals and the ligand-based π-system. By rotating the Cp rings, the hybridization, and thus the quantum interference, can be mechanically controlled, resulting in a conductance modulation that is seen experimentally.<br>

scholarly journals The halo model as a versatile tool to predict intrinsic alignments

2020 ◽  
Author(s):  
Maria Cristina Fortuna ◽  
Henk Hoekstra ◽  
Benjamin Joachimi ◽  
Harry Johnston ◽  
Nora Elisa Chisari ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Power Spectra ◽  
Stage Iv ◽  
Stage Iii ◽  
Radial Dependence ◽  
Additional Parameter ◽  
Small Scales ◽  
Cosmic Shear ◽  
Galaxy Populations ◽  
The Impact

Abstract Intrinsic alignments (IAs) of galaxies are an important contaminant for cosmic shear studies, but the modelling is complicated by the dependence of the signal on the source galaxy sample. In this paper, we use the halo model formalism to capture this diversity and examine its implications for Stage-III and Stage-IV cosmic shear surveys. We account for the different IA signatures at large and small scales, as well for the different contributions from central/satellite and red/blue galaxies, and we use realistic mocks to account for the characteristics of the galaxy populations as a function of redshift. We inform our model using the most recent observational findings: we include a luminosity dependence at both large and small scales and a radial dependence of the signal within the halo. We predict the impact of the total IA signal on the lensing angular power spectra, including the current uncertainties from the IA best-fits to illustrate the range of possible impact on the lensing signal: the lack of constraints for fainter galaxies is the main source of uncertainty for our predictions of the IA signal. We investigate how well effective models with limited degrees of freedom can account for the complexity of the IA signal. Although these lead to negligible biases for Stage-III surveys, we find that, for Stage-IV surveys, it is essential to at least include an additional parameter to capture the redshift dependence.

scholarly journals A Superfluid Perspective on Neutron Star Dynamics

Universe ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 17
Author(s):  
Nils Andersson
Keyword(s):  
Neutron Star ◽  
Degrees Of Freedom ◽  
Temperature Scale ◽  
Fluid System ◽  
Fluid Core ◽  
State Of Matter ◽  
Entrainment Effect ◽  
Neutron Component ◽  
The Impact

As mature neutron stars are cold (on the relevant temperature scale), one has to carefully consider the state of matter in their interior. The outer kilometre or so is expected to freeze to form an elastic crust of increasingly neutron-rich nuclei, coexisting with a superfluid neutron component, while the star’s fluid core contains a mixed superfluid/superconductor. The dynamics of the star depend heavily on the parameters associated with the different phases. The presence of superfluidity brings new degrees of freedom—in essence we are dealing with a complex multi-fluid system—and additional features: bulk rotation is supported by a dense array of quantised vortices, which introduce dissipation via mutual friction, and the motion of the superfluid is affected by the so-called entrainment effect. This brief survey provides an introduction to—along with a commentary on our current understanding of—these dynamical aspects, paying particular attention to the role of entrainment, and outlines the impact of superfluidity on neutron-star seismology.

scholarly journals A Traveler’s Guide to the Multiverse: Promises, Pitfalls, and a Framework for the Evaluation of Analytic Decisions

2021 ◽  
Vol 4 (1) ◽  
pp. 251524592095492
Author(s):  
Marco Del Giudice ◽  
Steven W. Gangestad
Keyword(s):  
Degrees Of Freedom ◽  
A Priori ◽  
Simulated Data ◽  
Style Analysis ◽  
Data Set ◽  
Scant Attention ◽  
Equivalence Type ◽  
The Impact ◽  
Biased Estimates

Decisions made by researchers while analyzing data (e.g., how to measure variables, how to handle outliers) are sometimes arbitrary, without an objective justification for choosing one alternative over another. Multiverse-style methods (e.g., specification curve, vibration of effects) estimate an effect across an entire set of possible specifications to expose the impact of hidden degrees of freedom and/or obtain robust, less biased estimates of the effect of interest. However, if specifications are not truly arbitrary, multiverse-style analyses can produce misleading results, potentially hiding meaningful effects within a mass of poorly justified alternatives. So far, a key question has received scant attention: How does one decide whether alternatives are arbitrary? We offer a framework and conceptual tools for doing so. We discuss three kinds of a priori nonequivalence among alternatives—measurement nonequivalence, effect nonequivalence, and power/precision nonequivalence. The criteria we review lead to three decision scenarios: Type E decisions (principled equivalence), Type N decisions (principled nonequivalence), and Type U decisions (uncertainty). In uncertain scenarios, multiverse-style analysis should be conducted in a deliberately exploratory fashion. The framework is discussed with reference to published examples and illustrated with the help of a simulated data set. Our framework will help researchers reap the benefits of multiverse-style methods while avoiding their pitfalls.

scholarly journals A Scheme for Controlled Cyclic Asymmetric Remote State Preparation in Noisy Environment

2021 ◽  
Vol 11 (4) ◽  
pp. 1405
Author(s):  
Nan Zhao ◽  
Tingting Wu ◽  
Yan Yu ◽  
Changxing Pei
Keyword(s):  
Quantum Information ◽  
Information Transmission ◽  
Remote State Preparation ◽  
Quantum Computers ◽  
Noisy Environment ◽  
State Preparation ◽  
Channel Expression ◽  
Actual Environment ◽  
The Impact ◽  
Multi Mode

As research on quantum computers and quantum information transmission deepens, the multi-particle and multi-mode quantum information transmission has been attracting increasing attention. For scenarios where multi-parties transmit sequentially increasing qubits, we put forward a novel (N + 1)-party cyclic remote state preparation (RSP) protocol among an arbitrary number of players and a controller. Specifically, we employ a four-party scheme in the case of a cyclic asymmetric remote state preparation scheme and demonstrate the feasibility of the scheme on the IBM Quantum Experience platform. Furthermore, we present a general quantum channel expression under different circulation directions based on the n-party. In addition, considering the impact of the actual environment in the scheme, we discuss the feasibility of the scheme affected by different noises.

scholarly journals Epipregnanolone as a Positive Modulator of GABAA Receptor in Rat Cerebellar and Hippocampus Neurons

Biomolecules ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 791
Author(s):  
Julia Bukanova ◽  
Elena Solntseva ◽  
Rodion Kondratenko ◽  
Eva Kudova
Keyword(s):  
Gabaa Receptor ◽  
Purkinje Cells ◽  
Hippocampal Neurons ◽  
Pyramidal Neurons ◽  
Patch Clamp Technique ◽  
Dual Effect ◽  
Combined Application ◽  
Gabaa Receptor Antagonist ◽  
Positive Modulator ◽  
Endogenous Steroid

Epipregnanolone (3β-hydroxy-5β-pregnan-20-one, Epi) is an endogenous steroid with important physiological effects and high affinity for GABAA receptors. The effect of Epi on GABA-induced chloride current (IGABA) in native neurons has hardly been studied. In this work, we studied the influence of Epi on the IGABA in the Purkinje cells of rat cerebellum and pyramidal neurons of rat hippocampus with the patch clamp technique. We showed that Epi is a positive modulator of the IGABA with EC50 of 5.7 µM in Purkinje cells and 9.3 µM in hippocampal neurons. Epi-induced potentiation of the IGABA was more potent at low vs. high GABA concentrations. Isopregnanolone (3β-hydroxy-5α-pregnan-20-one, Iso) counteracted Epi, reducing its potentiating effect by 2–2.3 times. Flumazenil, a nonsteroidal GABAA receptor antagonist, does not affect the Epi-induced potentiation. Comparison of the potentiating effects of Epi and allopregnanolone (3α-hydroxy-5α-pregnan-20-one, ALLO) showed that ALLO is, at least, a four times more potent positive modulator than Epi. The combined application of ALLO and Epi showed that the effects of these two steroids are not additive. We conclude that Epi has a dual effect on the IGABA increasing the current in the control solution and decreasing the stimulatory effect of ALLO.

Blockage of IL-17 Ameliorates Aβ-Induced Neurotoxicity and Cognitive Decline

2021 ◽  
Author(s):  
Yulan Liu ◽  
Yang Meng ◽  
Chenliang Zhou ◽  
Wenfang Xia ◽  
Lu Wang ◽  
...  
Keyword(s):  
Cognitive Decline ◽  
Lateral Ventricle ◽  
Hippocampal Neurons ◽  
Cognitive Impairments ◽  
Critical Role ◽  
Synaptic Dysfunction ◽  
Neural Damage ◽  
Primary Hippocampal Neurons ◽  
The Impact ◽  
Aβ Production

Abstract BackgroundNeuroinflammation plays a critical role in the pathophysiology of Alzheimer’s disease (AD), particularly in amyloid-β (Aβ) production. But the impact of the cytokine, interleukin-17A (IL-17) on the course of AD has not been well defined. The goal was to determine the effect of IL-17 on neural damage and whether IL-17 inhibitor (Y-320) could ameliorate Aβ-induced neurotoxicity and cognitive decline.MethodsThe expression level of IL-17 was analyzed in APP/PS1 mice. Then IL-17 was injected into the lateral ventricle of C57BL WT mice and roles on synaptic dysfunction and cognitive impairments were examined. Aβ42 was injected into the lateral ventricle of to mimic Aβ42 model mice. The effects of IL-17 inhibitor by oral gavage on Aβ42-induced neurotoxicity and cognitive decline were examined. ResultsWe found that IL-17 was increased in the hippocampus of APP/PS1 transgenic mouse, which has a fundamental role in mediating brain damage in neuroinflammatory processes. Furthermore, we reported that IL-17 was administrated in primary hippocampal neurons, leading to neural damage and synaptic dysfunction. At the same time, IL-17 caused synaptic dysfunction and cognitive impairments accompanying with increased of Aβ levels in mice. In addition, we found that Y-320 could rescue Aβ42–induced neural damage in primary hippocampal neurons, and ameliorate neuronal damage and cognitive impairments in Aβ42 model mice. Interestingly, we observed that IL-17 upregulated the production of soluble amyloid precursor protein β (sAPPβ) and phosphorylation of APP at T668 (pT668), moreover, Y-320 inhibited the Aβ production by down-regulation the sAPPβ and pT668. Conclusions Blockage of IL-17 might ameliorate Aβ-induced neurotoxicity and cognitive decline. These results strongly demonstrate a potential therapeutic role for IL-17 inhibitor in AD.

Investigation on the Robustness of Rotor/Stator Contact Interactions with Respect to Small Mistuning

2021 ◽  
Author(s):  
Florence Nyssen ◽  
Alain Batailly
Keyword(s):  
Degrees Of Freedom ◽  
Design Stage ◽  
Contact Interactions ◽  
Reduced Basis ◽  
Amplification Factors ◽  
Bladed Disk ◽  
Nonlinear Amplification ◽  
Rotor Stator Interaction ◽  
Bending Modes ◽  
The Impact

Abstract In this work, the impact of small mistuning on rotor/stator contact interactions is investigated. First, a detailed study of a rotor/stator interaction between the first bending modes and the second engine order is presented in the tuned case. Then, a numerical investigation on the effect of mistuning on the studied rotor/stator contact interaction is carried out. In particular, a stochastic analysis is performed to evaluate the robustness of the interaction with respect to the mistuning level. Simulations are conducted using a reduced order model (ROM) of an industrial bladed disk that combines both physical degrees of freedom (along blades tip for contact treatment) and modal coordinates. Mistuning is introduced in the tuned ROM by means of a modified version of the component mode mistuning method that allows to keep physical degrees of freedom within the reduced basis. Nonlinear amplification factors, i.e. the amplification factors in the context of contact nonlinearities, are compared with their linear counterparts, the latter are computed using a linear forcing on each blade using a two nodal diameters traveling wave excitation on the mistuned and the tuned bladed disk. The comparison between the linear and nonlinear amplification factor for each sample highlights that no correlation exists between a mistuning pattern leading to high amplifications in a linear context or when contact nonlinearities are taken into account. Therefore, dedicated analyses on the effect of mistuning should be undertaken with contact nonlinearities considerations at the design stage especially if intentional mistuning is considered.

Task-Dependent Representations in Rat Hippocampal Place Neurons

1997 ◽  
Vol 78 (2) ◽  
pp. 597-613 ◽  
Author(s):  
Tsuneyuki Kobayashi ◽  
Hisao Nishijo ◽  
Masaji Fukuda ◽  
Jan Bures ◽  
Taketoshi Ono
Keyword(s):  
Open Field ◽  
Hippocampal Neurons ◽  
Hippocampal Formation ◽  
Movement Speed ◽  
Neuron Activity ◽  
Place Field ◽  
Complex Spike ◽  
Place Fields ◽  
Sequential Trials ◽  
Self Stimulation

Kobayashi, Tsuneyuki, Hisao Nishijo, Masaji Fukuda, Jan Bures, and Taketoshi Ono. Task-dependent representations in rat hippocampal place neurons. J. Neurophysiol. 78: 597–613, 1997. It is suggested that the hippocampal formation is essential to spatial representations by flexible encoding of diverse information during navigation, which includes not only externally generated sensory information such as visual and auditory sensation but also ideothetic information concerning locomotion (i.e., internally generated information such as proprioceptive and vestibular sensation) as well as information concerning reward. In the present study, we investigated how various types of information are represented in the hippocampal formation, by recording hippocampal complex-spike cells from rats that performed three types of place learning tasks in a circular open field with the use of intracranial self-stimulation as reward. The intracranial self-stimulation reward was delivered in the following three contexts: if the rat 1) entered an experimenter-determined reward place within the open field, and this place was randomly varied in sequential trials; 2) entered two specific places, one within and one outside the place field (an area identified by change in activity of a place neuron); or 3) entered an experimenter-specified place outside the place field. Because the behavioral trails during navigation were more constant in the second task than in the first task, ideothetic information concerning locomotion was more relevant to acquiring reward in the second task than in the first task. Of 43 complex-spike cells recorded, 37 displayed place fields under the first task. Of these 37 place neurons, 34 also had significant reward correlates only inside the place field. Although reward and place correlates of the place neuron activity did not change between the first and second tasks, neuronal correlates to behavioral variables for locomotion such as movement speed, direction, and turning angle significantly increased in the second task. Furthermore, 6 of 31 place neurons tested with the third task, in which the reward place was located outside the original place field, shifted place fields. The results indicated that neuronal correlates of most place neurons flexibly increased their sensitivity to relevant information in a given context and environment, and some place neurons changed the place field per se with place reward association. These results suggest two strategies for how hippocampal neurons incorporate an incredible variety of perceptions into a unified representation of the environment: through flexible use of information and the creation of new representations.

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