Fluctuating synaptic conductances recreate in-vivo-like activity in
neocortical neurons.
Alain Destexhe, Michael Rudolph, Jean-Marc Fellous and Terrence J Sejnowski
Neuroscience 107: 13-24, 2001.
Abstract:
To investigate the basis of the fluctuating activity present in neocortical
neurons in vivo, we have combined computational models with whole-cell
recordings using the dynamic-clamp technique. A simplified
``point-conductance'' model was used to represent the currents generated by
thousands of stochastically-releasing synapses. Synaptic activity was
represented by two independent fast glutamatergic and GABAergic conductances
described by stochastic random-walk processes. An advantage of this approach
is that all the model parameters can be determined from voltage-clamp
experiments. We show that the point-conductance model captures the amplitude
and spectral characteristics of the synaptic conductances during background
activity. To determine if it can recreate in-vivo--like activity, we
injected this point-conductance model into a single-compartment model, or in
rat prefrontal cortical neurons in vitro using dynamic-clamp. This
procedure successfully recreated several properties of neurons
intracellularly-recorded in-vivo, such as a depolarized membrane
potential, the presence of high-amplitude membrane potential fluctuations, a
low input resistance and irregular spontaneous firing activity. In addition,
the point-conductance model could simulate the enhancement of responsiveness
due to background activity. We conclude that many of the characteristics of
cortical neurons in vivo can be explained by fast glutamatergic and
GABAergic conductances varying stochastically.
NEURON Demo:
The original NEURON programs that served to simulate this model are
also available.
This package simulates synaptic background activity similar to in vivo
measurements using a model of fluctuating synaptic conductances. This
"point-conductance" model recreates in-vivo-like membrane parameters,
such as the depolarized level, the low input resistance, high-amplitude
membrane potential fluctuations and irregular firing activity. This model
is fast enough to be simulated in real time, and has been used to recreate
in-vivo-like activity in real neurons in vitro, using
dynamic-clamp (see details in paper below). The mechanisms included are the
Na+ and K+ currents for generating action potentials (INa, IKd), the slow
voltage-dependent K+ current (IM) and the fluctuating synaptic conductances
(Gfluct).
There are further instructions in the README file.
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