scholarly journals Somatodendritic HCN channels in hippocampal OLM cells revealed by a convergence of computational models and experiments

2019 ◽  
Author(s):  
Vladislav Sekulić ◽  
Feng Yi ◽  
Tavita Garrett ◽  
Alexandre Guet-McCreight ◽  
Yvette Y. Lopez ◽  
...  
Keyword(s):  
Computational Models ◽  
Immunohistochemical Localization ◽  
Hcn Channels ◽  
Biophysical Properties ◽  
Resonance Frequencies ◽  
Mouse Hippocampus ◽  
Spatially Extended ◽  
H Channels ◽  
Whole Cell Recordings ◽  
Insight Into

AbstractDetermining details of spatially extended neurons is a challenge that needs to be overcome. The oriens-lacunosum/moleculare (OLM) interneuron has been implicated as a critical controller of hippocampal memory making it essential to understand how its biophysical properties contribute to function. We previously used computational models to show that OLM cells exhibit theta spiking resonance frequencies that depend on their dendrites having hyperpolarization-activated cation channels (h-channels). However, whether OLM cells have dendritic h-channels is unknown. We performed a set of whole-cell recordings of OLM cells from mouse hippocampus and constructed multi-compartment models using morphological and electrophysiological parameters extracted from the same cell. The models matched experiments only when dendritic h-channels were present. Immunohistochemical localization of the HCN2 subunit confirmed dendritic expression. These models can be used to obtain insight into hippocampal function. Our work shows that a tight integration of model and experiment tackles the challenge of characterizing spatially extended neurons.

scholarly journals Live imaging of neurogenesis in the adult mouse hippocampus

Science ◽  
2018 ◽  
Vol 359 (6376) ◽  
pp. 658-662 ◽  
Author(s):  
Gregor-Alexander Pilz ◽  
Sara Bottes ◽  
Marion Betizeau ◽  
David J. Jörg ◽  
Stefano Carta ◽  
...  
Keyword(s):  
Adult Mouse ◽  
Hippocampal Neurogenesis ◽  
Cell Fates ◽  
Comprehensive Description ◽  
Mouse Hippocampus ◽  
Asymmetric Divisions ◽  
Stem And Progenitor Cells ◽  
Newborn Neurons ◽  
Insight Into

Neural stem and progenitor cells (NSPCs) generate neurons throughout life in the mammalian hippocampus. We used chronic in vivo imaging and followed genetically labeled individual NSPCs and their progeny in the mouse hippocampus for up to 2 months. We show that NSPCs targeted by the endogenous Achaete-scute homolog 1 (Ascl1) promoter undergo limited rounds of symmetric and asymmetric divisions, eliciting a burst of neurogenic activity, after which they are lost. Further, our data reveal unexpected asymmetric divisions of nonradial glia-like NSPCs. Cell fates of Ascl1-labeled lineages suggest a developmental-like program involving a sequential transition from a proliferative to a neurogenic phase. By providing a comprehensive description of lineage relationships, from dividing NSPCs to newborn neurons integrating into the hippocampal circuitry, our data offer insight into how NSPCs support life-long hippocampal neurogenesis.

Sensitivity of Acoustic Resonance Properties to a Change in Volume of Piriform Sinuses

2016 ◽  
Vol 821 ◽  
pp. 671-676 ◽  
Author(s):  
Vojtěch Radolf
Keyword(s):  
Computational Models ◽  
Vocal Tract ◽  
Acoustic Resonance ◽  
Mode Shapes ◽  
Finite Element Models ◽  
Antiresonance Frequency ◽  
Resonance Frequencies ◽  
Resonance Properties ◽  
1D Model

Piriform sinuses (PS), side branches of the human vocal tract, produce extra resonances and antiresonances which influence the quality of produced voice. These acoustic resonant characteristics can be numerically simulated by 3D finite element models of the vocal tract with lateral cavities. Computations that use these accurate methods are very time consuming, therefore this study introduces a simplified 1D mathematical model to analyse acoustical effects of side branches. Although the 1D model cannot capture higher-frequency transversal mode shapes, the resulted changes caused by piriform sinuses partially correspond to recent findings of 3D computational models. New pair of resonances around 5 kHz followed by an antiresonance frequency were detected in the results of the model including PS. The first four resonance frequencies lying below the first new resonance of PS decreased with increasing PS volume and similarly both the new resonances of PS. The higher original resonances increased with increasing PS volume.

scholarly journals Detection of Harmonic Overvoltage and Resonance in AC Railways Using Measured Pantograph Electrical Quantities

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5645 ◽  
Author(s):  
Andrea Mariscotti ◽  
Leonardo Sandrolini
Keyword(s):  
Power Spectra ◽  
Rolling Stock ◽  
Short Time Fourier Transform ◽  
Power Stations ◽  
Resonance Frequencies ◽  
Energy Metering ◽  
Short Time ◽  
Insight Into ◽  
Over Time ◽  
Traction Power

Harmonic resonances are part of the power quality (PQ) problems of electrified railways and have serious consequences for the continuity of service and integrity of components in terms of overvoltage stress. The interaction between traction power stations (TPSs) and trains that causes line resonances is briefly reviewed, showing the dependence on infrastructure conditions. The objective is monitoring of resonance conditions at the onboard pantograph interface, which is new with respect to the approaches proposed in the literature and is equally applicable to TPS terminals. Voltage and current spectra, and derived impedance and power spectra, are analyzed, proposing a compact and efficient method based on short-time Fourier transform that is suitable for real-time implementation, possibly with the hardware available onboard for energy metering and harmonic interference monitoring. The methods are tested by sweeping long recordings taken at some European railways, covering cases of longer and shorter supply sections, with a range of resonance frequencies of about one decade. They give insight into the spectral behavior of resonances, their dependency on position and change over time, and the criteria needed to recognize genuine infrastructure resonances from rolling stock emissions.

scholarly journals Quantification and selection of ictogenic zones in epilepsy surgery

2019 ◽  
Author(s):  
Petroula Laiou ◽  
Eleftherios Avramidis ◽  
Marinho A. Lopes ◽  
Eugenio Abela ◽  
Michael Müller ◽  
...  
Keyword(s):  
Computational Models ◽  
Brain Networks ◽  
Network Models ◽  
Combinatorial Problem ◽  
Valuable Insight ◽  
Potential Applicability ◽  
Healthy Functioning ◽  
The Brain ◽  
Insight Into ◽  
Selection Of

AbstractNetwork models of brain dynamics provide valuable insight into the healthy functioning of the brain and how this breaks down in disease. A pertinent example is the use of network models to understand seizure generation (ictogenesis) in epilepsy. Recently, computational models have emerged to aid our understanding of seizures and to predict the outcome of surgical perturbations to brain networks. Such approaches provide the opportunity to quantify the effect of removing regions of tissue from brain networks and thereby search for the optimal resection strategy.Here, we use computational models to elucidate how sets of nodes contribute to the ictogenicity of networks. In small networks we fully elucidate the ictogenicity of all possible sets of nodes and demonstrate that the distribution of ictogenicity across sets depends on network topology. However, the full elucidation is a combinatorial problem that becomes intractable for large networks. Therefore, we develop a global optimisation approach to search for minimal sets of nodes that contribute significantly to ictogenesis. We demonstrate the potential applicability of these methods in practice by identifying optimal sets of nodes to resect in networks derived from 20 individuals who underwent resective surgery for epilepsy.

scholarly journals Tracing and visualisation of contributing water sources in the LISFLOOD-FP model of flood inundation

2021 ◽  
Author(s):  
Matthew D. Wilson ◽  
Thomas J. Coulthard
Keyword(s):  
Computational Models ◽  
Water Source ◽  
Water Sources ◽  
Flood Inundation ◽  
Simple Method ◽  
Source Tracing ◽  
Shallow Estuary ◽  
Flow Pathways ◽  
Flood Dynamics ◽  
Insight Into

Abstract. We describe the formulation of a simple method of water source tracing for computational models of flood inundation and demonstrate its implementation within CAESAR-Lisflood. Water source tracing can provide additional insight into flood dynamics by accounting for flow pathways. The method developed is independent of the hydraulic formulation used, allowing it to be implemented in other model codes without affecting flow routing. In addition, we developed a method which allows up to three water sources to be visualised in RGB colour-space, while continuing to allow depth to be resolved. We show the application of the methods developed for example applications of a major flood event, a shallow estuary, and Amazonian wetland inundation. A key advantage of the formulation developed is that the number of water sources which may be traced is limited only by computational considerations. In addition, the method is independent of the hydraulic formulation, meaning that it is relatively straightforward to add to existing finite volume codes including those based on or developed around the LISFLOOD-FP method.

scholarly journals Computational models of O-LM cells are recruited by low or high theta frequency inputs depending on h-channel distributions

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Vladislav Sekulić ◽  
Frances K Skinner
Keyword(s):  
Computational Models ◽  
Inhibitory Neurons ◽  
Delayed Rectifier ◽  
Wide Range ◽  
Theta Frequency ◽  
Link Model ◽  
Conductance States ◽  
Model Database ◽  
H Channels ◽  
High Conductance

Although biophysical details of inhibitory neurons are becoming known, it is challenging to map these details onto function. Oriens-lacunosum/moleculare (O-LM) cells are inhibitory cells in the hippocampus that gate information flow, firing while phase-locked to theta rhythms. We build on our existing computational model database of O-LM cells to link model with function. We place our models in high-conductance states and modulate inhibitory inputs at a wide range of frequencies. We find preferred spiking recruitment of models at high (4–9 Hz) or low (2–5 Hz) theta depending on, respectively, the presence or absence of h-channels on their dendrites. This also depends on slow delayed-rectifier potassium channels, and preferred theta ranges shift when h-channels are potentiated by cyclic AMP. Our results suggest that O-LM cells can be differentially recruited by frequency-modulated inputs depending on specific channel types and distributions. This work exposes a strategy for understanding how biophysical characteristics contribute to function.

scholarly journals A Trypanosoma brucei orphan kinesin employs a convergent microtubule organization strategy to complete cytokinesis

2021 ◽  
Author(s):  
Thomas E Sladewski ◽  
Paul C Campbell ◽  
Neil Billington ◽  
Alexandra D'Ordine ◽  
Christopher L de Graffenried
Keyword(s):  
Trypanosoma Brucei ◽  
Biophysical Properties ◽  
Microtubule Organization ◽  
Division Plane ◽  
Mechanistic Insight ◽  
Organization Strategy ◽  
Cytoskeletal Elements ◽  
Order Structures ◽  
Insight Into

Many single-celled eukaryotes have complex cell morphologies defined by cytoskeletal elements comprising microtubules arranged into higher-order structures. Trypanosoma brucei (T. brucei) cell polarity is mediated by a parallel array of microtubules that underlie the plasma membrane and define the auger-like shape of the parasite. The subpellicular array must be partitioned and segregated using a microtubule-based mechanism during cell division. We previously identified an orphan kinesin, KLIF, that localizes to the division plane and is essential for the completion of cytokinesis. To gain mechanistic insight into how this novel kinesin functions to complete cleavage furrow ingression, we characterized the biophysical properties of the KLIF motor domain in vitro. We found that KLIF is a non-processive dimeric kinesin that dynamically crosslinks microtubules. Microtubules crosslinked in an antiparallel orientation are translocated relative to one another by KLIF, while microtubules crosslinked parallel to one another remain static, resulting in the formation of organized parallel bundles. In addition, we found that KLIF stabilizes the alignment of microtubule plus ends. These features provide a mechanistic understanding for how KLIF functions to form a new pole of aligned microtubule plus ends that defines the shape of the new posterior, which is a unique requirement for the completion of cytokinesis in T. brucei.

Ultimate Strength of the Adventitia and Media of Human Atherosclerotic Carotid Arteries in the Axial and Circumferential Directions

2009 ◽  
Author(s):  
Zhongzhao Teng ◽  
Allen H. Hoffman ◽  
Jie Zheng ◽  
Pamela K. Woodard ◽  
Dalin Tang
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Atherosclerotic Plaque ◽  
Balloon Angioplasty ◽  
Cardiovascular Events ◽  
Computational Models ◽  
Carotid Arteries ◽  
Material Strength ◽  
Rupture Mechanism ◽  
Insight Into

The abrupt closure of an artery by an occlusive thrombus is the main cause of myocardial infarcts and other thrombotic sequelae of atherosclerosis. This thrombosis is often associated with rupture of an atherosclerotic plaque [1,2]. Histology has shown that most rupture sites are also sites of increased mechanical stress [2]. It has been widely accepted that atherosclerosis leads to locally increased stresses in the region of lesions. However, validation of this hypothesis has been impeded by a lack of experimental data on the material strength of atherosclerotic tissues. Knowledge of mechanical properties of human atherosclerotic tissues is essential for understanding the rupture mechanism and also for creating more accurate computational models for predicting fatal cardiovascular events [3]. Moreover, an increased understanding of the mechanical properties of atherosclerotic tissue is important for developing greater insight into the pathophysiology of the cardiovascular system and as well as for predicting the outcome of interventional treatments such as balloon angioplasty.

Vibration transmissions and predictions within low-rise buildings above throat area in the metro depot

2021 ◽  
pp. 107754632110576
Author(s):  
Ziyu Tao ◽  
Chao Zou ◽  
Yimin Wang ◽  
Jie Wu
Keyword(s):  
Finite Element Method ◽  
Structural Design ◽  
Field Measurements ◽  
The Finite Element Method ◽  
Human Comfort ◽  
Resonance Frequencies ◽  
Vibration Responses ◽  
Frequency Components ◽  
Floor Vibration ◽  
Insight Into

Train-induced feelable vibrations can bring side effects to people living or working in the building, as well as to operation of precise equipment. As massive construction of over-track buildings above metro depots prevails in megacities, impacts from train-induced feelable vibration take more concern. Four standard-designed 4-story steel-framed offices above the throat area in the Qianhai metro depot in Shenzhen, China, are studied in this research. The field measurements were conducted to investigate the influences of track alignment and track location in the throat area on vibration responses of over-track buildings. Detailed vibration analyses using the finite element method have been conducted. Train-induced floor vibration assessments on human comfort are carried out based on a total of 54 train pass-bys operated in the morning and evening and on different tracks. It can be found that the track alignment primarily affected the higher frequency components of train-induced vibrations, where curved trackinduced vibrations have larger amplitudes. The variance of train-induced building vibrations among pass-bys on different track locations was reduced compared with that of ground vibrations because of the averaging effects caused by multiple transmitting paths within the massive platform and stiff transfer structures. Train-induced acceleration levels at mid-floor can be 20–25 dB larger than those near columns at floor resonance frequencies which are dependent on the structural design. This research gives a comprehensive insight into train-induced vibrations within low-rise steel-framed buildings above the throat area in the metro depot, which is a valuable reference for assessments before the construction of future similar over-track communities.

Investigating human prediction: sequence termination provides insights into predictive statistics

2021 ◽  
Author(s):  
Isaac Treves
Keyword(s):  
Computational Models ◽  
Frequency Estimation ◽  
Reaction Time Task ◽  
Prior Exposure ◽  
Human Cognition ◽  
Passive Exposure ◽  
Future Work ◽  
Best Fit ◽  
Prediction Sequence ◽  
Insight Into

Prediction is a fundamental process in human cognition. Prediction means extracting one or more statistics from the distribution of past inputs and using that information to make a decision. What are the statistics underlying human predictions, and how do they change with training? To investigate these questions, we designed a sequence termination task, where participants watch temporally unfolding sequences and terminate them when they can predict the next item. We then test how well the participants’ termination points are predicted by computational models. We contrast frequency estimation models (How often did this symbol appear in the sequence?), transition models (How often did symbol A follow symbol B?), and a chunking model (What are the patterns of symbols?). In an online experiment with 65 adults, we find that participants are best fit by a transition-counting model. To assess the effect of training, we manipulated passive exposure to the sequences prior to the sequence termination task. Contrary to our expectations, prior exposure to sequences had no effect on termination performance– whether tested statistically or computationally, and despite good power. Lastly, training specifically on the termination task may shift responses towards chunking. These results provide insight into the representations, or information in mind, behind prediction. However, the lack of an effect of prior exposure makes it clear that sequence termination measures explicit, or conscious, prediction. Future work could examine whether representations in explicit prediction tasks like sequence termination are different from implicit, or unconscious, tasks like the serial reaction time task.

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