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.

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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.

NEURON demo:

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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