scholarly journals Small dendritic synapses enhance temporal coding in a model of cochlear nucleus bushy cells

2020 ◽  
Author(s):  
Elisabeth Koert ◽  
Thomas Kuenzel
Keyword(s):  
Membrane Potential ◽  
Cochlear Nucleus ◽  
Temporal Coding ◽  
Fine Tuning ◽  
Model Parameters ◽  
Biophysical Parameters ◽  
Temporal Precision ◽  
Main Input ◽  
The Impact ◽  
Bushy Cells

AbstractSpherical bushy cells (SBC) in the the anteroventral cochlear nucleus can improve the temporal precision of the auditory nerve spiking activity despite receiving sometimes only a single suprathreshold axosomatic input. The interaction with small dendritic inputs could provide a possible explanation for this phenomenon. In a compartment model of spherical bushy cells with a stylized or realistic three-dimensional representation of the bushy dendrite we explored this proposal. Phase-locked dendritic inputs caused both a tonic depolarization and a modulation of the SBC membrane potential at the frequency of the stimulus but for plausible model parameters do not cause output action potentials (AP). The tonic depolarization increased the excitability of the SBC model. The modulation of the membrane potential caused a phase-dependent increase in the efficacy of the main axosomatic input to cause output AP. These effects increased the rate and the temporal precision of output AP. Rate was mainly increased for stimulus frequencies at and below the characteristic frequency of the main input. Precision mostly increased for higher frequencies above about 1 kHz. Dendritic morphological parameters, biophysical parameters of the dendrite and the synaptic inputs and tonotopic parameters of the inputs all affected the impact of dendritic synapses. This suggested the possibility of fine tuning of the effect the dendritic inputs have for different coding demands or input frequency ranges. Excitatory dendritic inputs modulate the processing of the main input and are thus a plausible mechanism for the improvement of temporal precision in spherical bushy cells.

scholarly journals Small dendritic synapses enhance temporal coding in a model of cochlear nucleus bushy cells

2021 ◽  
Author(s):  
Elisabeth Koert ◽  
Thomas Kuenzel
Keyword(s):  
Membrane Potential ◽  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Stimulus Frequency ◽  
Dendritic Tree ◽  
Temporal Coding ◽  
Functional Explanation ◽  
Model Parameters ◽  
Temporal Precision ◽  
Bushy Cells

Spherical bushy cells (SBCs) in the the anteroventral cochlear nucleus receive a single or very few powerful axosomatic inputs from the auditory nerve. However, SBCs are also contacted by small regular bouton synapses of the auditory nerve, located in their dendritic tree. The function of these small inputs is unknown. It was speculated that the interaction of axosomatic inputs with small dendritic inputs improved temporal precision, but direct evidence for this is missing. In a compartment model of spherical bushy cells with a stylized or realistic 3D-representation of the bushy dendrite we thus explored this proposal. Phase-locked dendritic inputs caused both tonic depolarization and a modulation of the model SBC membrane potential at the frequency of the stimulus. For plausible model parameters dendritic inputs were subthreshold. Instead, the tonic depolarization increased the excitability of the SBC model and the modulation of the membrane potential caused a phase-dependent increase in the efficacy of the main axosomatic input. This improved rate, entrainment and temporal precision of output action potentials. However, these effects showed differential dependency on the stimulus frequency. A careful exploration of morphological and biophysical parameters of the bushy dendrite suggested a functional explanation for the peculiar shape of the bushy dendrite. Our model for the first time directly implied a role for the small excitatory dendritic inputs in auditory processing: they modulate the efficacy of the main input and are thus a plausible mechanism for the improvement of temporal precision and fidelity in these central auditory neurons.

Pierre3D: a 3D stochastic rockfall simulator based on random ground roughness and hyperbolic restitution factors

2015 ◽  
Vol 52 (9) ◽  
pp. 1360-1373 ◽  
Author(s):  
Valentin S. Gischig ◽  
Oldrich Hungr ◽  
Andrew Mitchell ◽  
Franck Bourrier
Keyword(s):  
Stochastic Process ◽  
Slope Angle ◽  
Test Site ◽  
Fine Tuning ◽  
Model Parameters ◽  
Observation Data ◽  
Lumped Mass ◽  
Forest Road ◽  
Rockfall Hazard ◽  
The Impact

The use of dynamic computational methods has become indispensable for addressing problems related to rockfall hazard. Although a number of models with various degrees of complexity are available, model parameters are rarely calibrated against observations from rockfall experiments. A major difficulty lies in reproducing the apparent randomness of the impact process related to both ground and block irregularities. Calibration of rigorous methods capable of explicitly modeling trajectories and impact physics of irregular blocks is difficult, as parameter spaces become too vast and the quality of model input and observation data are insufficient. The model presented here returns to the simple “lumped-mass” approach and simulates the characteristic randomness of rockfall impact as a stochastic process. Despite similarities to existing approaches, the model presented here incorporates several novel concepts: (i) ground roughness and particle roughness are represented as a random change of slope angle at impact; (ii) lateral deviations of rebound direction from the trajectory plane at impact are similarly accounted for by perturbing the ground orientation laterally, thus inducing scatter of run-out directions; and (iii) a hyperbolic relationship connects restitution factors to impact deformation energy. With these features, the model is capable of realistically accounting for the influence of particle mass on dynamic behaviour. The model only requires four input parameters, rendering it flexible for calibration against observed datasets. In this study, we calibrate the model against observations from the rockfall test site at Vaujany in France. The model is able to reproduce observed distributions of velocity, jump heights, and runout at observation points. In addition, the spatial distribution of the trajectories and landing points has been successfully simulated. Different parameter sets have been used for different ground materials such as an avalanche channel, a forest road, and a talus cone. Further calibration of the new model against a range of field datasets is essential. This study is part of an extensive calibration program that is still in progress at this first presentation of the method, and focuses on fine-tuning the details of the stochastic process implemented both in two-dimensional (2D) and three-dimensional (3D) versions of the model.

Differential contributions of voltage-gated potassium channel subunits in enhancing temporal coding in the bushy cells of the ventral cochlear nucleus

2021 ◽  
Author(s):  
Mingyu Fu ◽  
Lu Zhang ◽  
Xiao Xie ◽  
Ningqian Wang ◽  
Zhongju Xiao
Keyword(s):  
Cochlear Nucleus ◽  
Spike Timing ◽  
Temporal Coding ◽  
Membrane Properties ◽  
Membrane Excitability ◽  
Patch Clamp Recording ◽  
Voltage Gated ◽  
Ventral Cochlear Nucleus ◽  
Kv Channels ◽  
Bushy Cells

Temporal coding precision of bushy cells in the ventral cochlear nucleus (VCN), critical for sound localization and communication, depends on the generation of rapid and temporally precise action potentials (APs). Voltage-gated potassium (Kv) channels are critically involved in this. The bushy cells in rat VCN express Kv1.1, 1.2, 1.3, 1.6, 3.1, 4.2 and 4.3 subunits. The Kv1.1 subunit contributes to the generation of a temporally precise single AP. However, the understanding of the functions of other Kv subunits expressed in the bushy cells is limited. Here, we investigated the functional diversity of Kv subunits concerning their contributions to temporal coding. We characterized the electrophysiological properties of the Kv channels with different subunits using whole-cell patch-clamp recording and pharmacological methods. The neuronal firing pattern changed from single to multiple APs only when the Kv1.1 subunit was blocked. The Kv subunits, including the Kv1.1, 1.2, 1.6 or 3.1, were involved in enhancing temporal coding by lowering membrane excitability, shortening AP latencies, reducing jitter and regulating AP kinetics. Meanwhile, all the Kv subunits contributed to rapid repolarization and sharpening peaks by narrowing half-width and accelerating fall rate, while the Kv1.1 subunit also affected the depolarization of AP. The Kv1.1, 1.2 and 1.6 subunits endowed bushy cells with a rapid time constant and a low input resistance of membrane for enhancing spike timing precision. The present results indicate that the Kv channels differentially affect intrinsic membrane properties to optimize the generation of rapid and reliable APs for temporal coding.

Voltage-Sensitive Conductances of Bushy Cells of the Mammalian Ventral Cochlear Nucleus

2007 ◽  
Vol 97 (6) ◽  
pp. 3961-3975 ◽  
Author(s):  
Xiao-Jie Cao ◽  
Shalini Shatadal ◽  
Donata Oertel
Keyword(s):  
Cochlear Nucleus ◽  
Low Voltage ◽  
Nerve Fibers ◽  
Superior Olivary Complex ◽  
Voltage Sensitivity ◽  
Sound Sources ◽  
Temporal Precision ◽  
Ventral Cochlear Nucleus ◽  
Cation Conductance ◽  
Bushy Cells

Bushy cells in the ventral cochlear nucleus convey firing of auditory nerve fibers to neurons in the superior olivary complex that compare the timing and intensity of sounds at the two ears and enable animals to localize sound sources in the horizontal plane. Three voltage-sensitive conductances allow bushy cells to convey acoustic information with submillisecond temporal precision. All bushy cells have a low-voltage-activated, α-dendrotoxin (α-DTX)-sensitive K+ conductance ( gKL) that was activated by depolarization past −70 mV, was half-activated at −39.0 ± 1.7 (SE) mV, and inactivated ∼60% over 5 s. Maximal gKL varied between 40 and 150 nS (mean: 80.8 ± 16.7 nS). An α-DTX-insensitive, tetraethylammonium (TEA)-sensitive, K+ conductance ( gKH) was activated at voltages positive to −40 mV, was half-activated at −18.1 ± 3.8 mV, and inactivated by 90% over 5 s. Maximal gKH varied between 35 and 80 nS (mean: 58.2 ± 6.5 nS). A ZD7288-sensitive, mixed cation conductance ( gh) was activated by hyperpolarization greater than −60 mV and half-activated at −83.1 ± 1.1 mV. Maximum gh ranged between 14.5 and 56.6 nS (mean: 30.0 ± 5.5 nS). 8-Br-cAMP shifted the voltage sensitivity of gh positively. Changes in temperature stably altered the steady-state magnitude of Ih. Both gKL and gKH contribute to repolarizing action potentials and to sharpening synaptic potentials. Those cells with the largest gh and the largest gKL fired least at the onset of a depolarization, required the fastest depolarizations to fire, and tended to be located nearest the nerve root.

The Continuum of Operating Modes for a Passive Model Neuron

1999 ◽  
Vol 11 (5) ◽  
pp. 1139-1154 ◽  
Author(s):  
Michael A. Kisley ◽  
George L. Gerstein
Keyword(s):  
Membrane Potential ◽  
Cortical Neurons ◽  
Action Potentials ◽  
Model Neuron ◽  
Operating Mode ◽  
Temporal Coding ◽  
Synaptic Activity ◽  
Full Spectrum ◽  
Temporal Precision ◽  
Operating Modes

Whether cortical neurons act as coincidence detectors or temporal integrators has implications for the way in which the cortex encodes information—by average firing rate or by precise timing of action potentials. In this study, we examine temporal coding by a simple passive-membrane model neuron responding to a full spectrum of multisynaptic input patterns, from highly coincident to temporally dispersed. The temporal precision of the model's action potentials varies continuously along the spectrum, depends very little on the number of synaptic inputs, and is shown to be tightly correlated with the mean slope of the membrane potential preceding the output spikes. These results are shown to be largely independent of the size of postsynaptic potentials, of random background synaptic activity, and of shape of the correlated multisynaptic input pattern. An experimental test involving membrane potential slope is suggested to help determine the basic operating mode of an observed cortical neuron.

scholarly journals Cerebello-Thalamic Spike Transfer via Temporal Coding and Cortical Adaptation

2020 ◽  
Author(s):  
Carmen B. Schäfer ◽  
Zhenyu Gao ◽  
Chris I. De Zeeuw ◽  
Freek E. Hoebeek
Keyword(s):  
Cerebral Cortex ◽  
Membrane Potential ◽  
Primary Motor Cortex ◽  
Temporal Coding ◽  
Fine Tuning ◽  
Action Potential Firing ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Single Action

AbstractOrchestrating the ensemble of muscle contractions necessary for coordinated movements requires the interaction of cerebellar, thalamic and cerebral structures, but the mechanisms underlying the integration of information remain largely unknown. Here we investigated how excitatory inputs from cerebellar nuclei (CN) and primary motor cortex layer VI (M1 L6) neurons may regulate together the activity of neurons in the mouse ventrolateral (VL) thalamus. Using dual-optogenetic stimulation and whole-cell recordings in vitro we were able to specifically activate the CN and M1 pathways and study their differential impact. We found that VL spiking probability is effectively determined by a pause in CN stimuli, whereas VL membrane potential can be modulated subthreshold by M1 L6 input. Upon mild depolarization of the VL membrane potential, repetitive CN stimulation evokes at best single action potential firing, whereas more negative membrane potentials increase VL spiking probability. Moreover, whereas high-frequency cerebellar activity attenuates thalamic spiking, pauses in cerebellar activity re-activate thalamic spiking. In contrast, facilitating inputs from cerebral cortex modulate thalamo-cortical spike transfer via fluctuations in the membrane potential. The fine-tuning by cerebellar and cerebral activity allows the motor thalamus to operate as a low-pass filter for cerebellar activity, generating sparse but precisely timed outputs for the cerebral cortex.

Fluorescent potentiometric dyes for membrane-potential imaging

1994 ◽  
Vol 52 ◽  
pp. 166-167
Author(s):  
Leslie M. Loew
Keyword(s):  
Membrane Potential ◽  
Single Cells ◽  
Quantitative Imaging ◽  
Optical Recording ◽  
Biological Processes ◽  
Major Focus ◽  
The Past ◽  
Excitable Systems ◽  
Major Application ◽  
The Impact

A major application of potentiometric dyes has been the multisite optical recording of electrical activity in excitable systems. After being championed by L.B. Cohen and his colleagues for the past 20 years, the impact of this technology is rapidly being felt and is spreading to an increasing number of neuroscience laboratories. A second class of experiments involves using dyes to image membrane potential distributions in single cells by digital imaging microscopy - a major focus of this lab. These studies usually do not require the temporal resolution of multisite optical recording, being primarily focussed on slow cell biological processes, and therefore can achieve much higher spatial resolution. We have developed 2 methods for quantitative imaging of membrane potential. One method uses dual wavelength imaging of membrane-staining dyes and the other uses quantitative 3D imaging of a fluorescent lipophilic cation; the dyes used in each case were synthesized for this purpose in this laboratory.

Food Safety Security: A new Concept for Enhancing Food Safety Measures

2012 ◽  
Vol 82 (3) ◽  
pp. 216-222 ◽  
Author(s):  
Venkatesh Iyengar ◽  
Ibrahim Elmadfa
Keyword(s):  
Food Safety ◽  
Hazard Analysis ◽  
Warning System ◽  
Shared Responsibility ◽  
Fine Tuning ◽  
Strategic Action ◽  
Surveillance Network ◽  
Measurement Systems ◽  
Critical Control Points ◽  
The Impact

The food safety security (FSS) concept is perceived as an early warning system for minimizing food safety (FS) breaches, and it functions in conjunction with existing FS measures. Essentially, the function of FS and FSS measures can be visualized in two parts: (i) the FS preventive measures as actions taken at the stem level, and (ii) the FSS interventions as actions taken at the root level, to enhance the impact of the implemented safety steps. In practice, along with FS, FSS also draws its support from (i) legislative directives and regulatory measures for enforcing verifiable, timely, and effective compliance; (ii) measurement systems in place for sustained quality assurance; and (iii) shared responsibility to ensure cohesion among all the stakeholders namely, policy makers, regulators, food producers, processors and distributors, and consumers. However, the functional framework of FSS differs from that of FS by way of: (i) retooling the vulnerable segments of the preventive features of existing FS measures; (ii) fine-tuning response systems to efficiently preempt the FS breaches; (iii) building a long-term nutrient and toxicant surveillance network based on validated measurement systems functioning in real time; (iv) focusing on crisp, clear, and correct communication that resonates among all the stakeholders; and (v) developing inter-disciplinary human resources to meet ever-increasing FS challenges. Important determinants of FSS include: (i) strengthening international dialogue for refining regulatory reforms and addressing emerging risks; (ii) developing innovative and strategic action points for intervention {in addition to Hazard Analysis and Critical Control Points (HACCP) procedures]; and (iii) introducing additional science-based tools such as metrology-based measurement systems.

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