Extracellular potentials and currents of a single active fiber in a restricted volume conductor

1990 ◽  
Vol 18 (3) ◽  
pp. 219-238 ◽  
Author(s):  
Natalia Trayanova ◽  
Craig S. Henriquez ◽  
Robert Plonsey
Keyword(s):  
Volume Conductor ◽  
Active Fiber ◽  
Restricted Volume ◽  
Extracellular Potentials

scholarly journals Multimodal modeling of neural network activity: computing LFP, ECoG, EEG and MEG signals with LFPy2.0

2018 ◽  
Author(s):  
Espen Hagen ◽  
Solveig Næss ◽  
Torbjørn V. Ness ◽  
Gaute T. Einevoll
Keyword(s):  
Neuronal Activity ◽  
Message Passing Interface ◽  
Dipole Moments ◽  
Volume Conductor ◽  
Network Activity ◽  
Head Model ◽  
Current Dipole ◽  
Link Type ◽  
Transmembrane Currents ◽  
Extracellular Potentials

AbstractRecordings of extracellular electrical, and later also magnetic, brain signals have been the dominant technique for measuring brain activity for decades. The interpretation of such signals is however nontrivial, as the measured signals result from both local and distant neuronal activity. In volume-conductor theory the extracellular potentials can be calculated from a distance-weighted sum of contributions from transmembrane currents of neurons. Given the same transmembrane currents, the contributions to the magnetic field recorded both inside and outside the brain can also be computed. This allows for the development of computational tools implementing forward models grounded in the biophysics underlying electrical and magnetic measurement modalities.LFPy (LFPy.readthedocs.io) incorporated a well-established scheme for predicting extracellular potentials of individual neurons with arbitrary levels of biological detail. It relies on NEURON (neuron.yale.edu) to compute transmembrane currents of multicompartment neurons which is then used in combination with an electrostatic forward model. Its functionality is now extended to allow for modeling of networks of multicompartment neurons with concurrent calculations of extracellular potentials and current dipole moments. The current dipole moments are then, in combination with suitable volume-conductor head models, used to compute non-invasive measures of neuronal activity, like scalp potentials (electroencephalographic recordings; EEG) and magnetic fields outside the head (magnetoencephalographic recordings; MEG). One such built-in head model is the four-sphere head model incorporating the different electric conductivities of brain, cerebrospinal fluid, skull and scalp.We demonstrate the new functionality of the software by constructing a network of biophysically detailed multicompartment neuron models from the Neocortical Microcircuit Collaboration (NMC) Portal (bbp.epfl.ch/nmc-portal) with corresponding statistics of connections and synapses, and compute in vivo-like extracellular potentials (local field potentials, LFP; electrocorticographical signals, ECoG) and corresponding current dipole moments. From the current dipole moments we estimate corresponding EEG and MEG signals using the four-sphere head model. We also show strong scaling performance of LFPy with different numbers of message-passing interface (MPI) processes, and for different network sizes with different density of connections.The open-source software LFPy is equally suitable for execution on laptops and in parallel on high-performance computing (HPC) facilities and is publicly available on GitHub.com.

Ephaptic transmission in squid giant axons

1978 ◽  
Vol 234 (5) ◽  
pp. C162-C169 ◽  
Author(s):  
F. Ramon ◽  
J. W. Moore
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Extracellular Volume ◽  
Giant Axons ◽  
Low Sodium ◽  
Ephaptic Transmission ◽  
Transmembrane Voltage ◽  
Restricted Volume ◽  
Small Voltage ◽  
Extracellular Potentials

Some characteristics of ephaptic transmission of action potentials were investigated with squid giant axons. For these studies two isolated axons were placed side by side or, on occasion, a single long axon was looped to form an "ephapse" between the axon trunk and one of its main branches. Extracellular potentials measured adjacent to axons surrounded by a very restricted volume of liquid ranged up to 80 mV in magnitude and had a shape similar to that of the membrane current. Intracellular records of the same axon regions show small voltage deflections; however, the transmembrane voltage (Vm = Vi - Vo) has the appearance of normally propagated action potentials. Ephaptic transmission of action potentials is possible when the ephaptic region is submerged in oil, as well as when the region is immersed in low-calcium solutions. When the speed of the propagated action potential is lowered by replacing the normal artifical seawater (ASW) with low-sodium ASW, some ephaptic effects are enhanced. It is concluded that in regions in which axons are confined by restricted extracellular volume, the large extracellular voltage changes arising during the passage of an action potential in one can cause ephaptic excitation in another.

Extracellular potentials of a single myelinated nerve fiber in an unbounded volume conductor

1989 ◽  
Vol 61 (3) ◽  
pp. 205-210 ◽  
Author(s):  
D. Stephanova ◽  
N. Trayanova ◽  
A. Gydikov ◽  
A. Kossev
Keyword(s):  
Nerve Fiber ◽  
Volume Conductor ◽  
Myelinated Nerve Fiber ◽  
Myelinated Nerve ◽  
Extracellular Potentials

The Role of Computer Modeling in Electrocardiography

1990 ◽  
Vol 29 (04) ◽  
pp. 282-288 ◽  
Author(s):  
A. van Oosterom
Keyword(s):  
Electrical Activity ◽  
Computer Modeling ◽  
Body Surface ◽  
Electrical Current ◽  
The Body ◽  
Volume Conductor ◽  
Current Generator ◽  
Cardiac Electrical Activity ◽  
Source Models

AbstractThis paper introduces some levels at which the computer has been incorporated in the research into the basis of electrocardiography. The emphasis lies on the modeling of the heart as an electrical current generator and of the properties of the body as a volume conductor, both playing a major role in the shaping of the electrocardiographic waveforms recorded at the body surface. It is claimed that the Forward-Problem of electrocardiography is no longer a problem. Several source models of cardiac electrical activity are considered, one of which can be directly interpreted in terms of the underlying electrophysiology (the depolarization sequence of the ventricles). The importance of using tailored rather than textbook geometry in inverse procedures is stressed.

scholarly journals The effect of dipole housing and feeding wires in physical phantoms for EEG

2019 ◽  
Vol 5 (1) ◽  
pp. 85-88
Author(s):  
René Machts ◽  
Alexander Hunold ◽  
Jens Haueisen
Keyword(s):  
Electric Potential ◽  
Volume Conductor ◽  
Constant Current ◽  
Twisted Pair ◽  
Eeg Data ◽  
Phantom Measurements ◽  
Average Change ◽  
Electric Potentials ◽  
The Difference ◽  
Signal Sources

AbstractCurrent dipoles are well established models in the localization of neuronal activity to electroencephalography (EEG) data. In physical phantoms, current dipoles can be used as signal sources. Current dipoles are often powered by constant current sources connected via twisted pair wires mostly consisting of copper. The poles are typically formed by platinum wires. These wires as well as the dipole housing might disturb the electric potential distributions in physical phantom measurements. We aimed to quantify this distortion by comparing simulation setups with and without the wires and the housing. The electric potential distributions were simulated using finite element method (FEM). We chose a homogenous volume conductor surrounding the dipoles, which was 100 times larger than the size of the dipoles. We calculated the difference of the electric potential at the surface of the volume conductor between the simulations with and without the connecting wires and the housing. Comparing simulations neglecting all connecting wires and the housing rod to simulations considering them, the electric potential at the surface of the volume conductor differed on average by 2.85 %. Both platinum and twisted pair copper wires had a smaller effect on the electric potentials with a maximum average change of 6.38 ppm. Consequently, source localization of measurements in physical head phantoms should consider these rods in the forward model.

scholarly journals Novel gas sensor combined active fiber loop ring-down and dual wavelengths differential absorption method

2014 ◽  
Vol 22 (9) ◽  
pp. 11244 ◽  
Author(s):  
Yanjie Zhao ◽  
Jun Chang ◽  
Jiasheng Ni ◽  
Qingpu Wang ◽  
Tongyu Liu ◽  
...  
Keyword(s):  
Gas Sensor ◽  
Absorption Method ◽  
Differential Absorption ◽  
Active Fiber ◽  
Loop Ring ◽  
Differential Absorption Method ◽  
Fiber Loop
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