Estimation of synaptic conductances and their variances from intracellular
recordings of neocortical neurons in vivo.
Michael Rudolph, Joe-Guillaume Pelletier, Denis Paré and Alain
Neurocomputing 58: 387-392, 2004.
During intense network activity, neocortical neurons are in a
``high-conductance'' state. To estimate the respective contributions of
excitatory and inhibitory conductances in generating such states, we combined
computational models with intracellular recordings obtained in cat parietal
cortex in vivo. Fitting a fluctuating-conductance model to the recordings
revealed that inhibitory conductances are dominant (several times larger than
excitation). Conductance variance (i.e., the ``noise'') was also larger for
inhibition, indicating that inhibitory dynamics has a pronounced impact on
membrane potential fluctuations. We conclude that the synaptic bombardment of
neocortical neurons in vivo is not excitatory, but mostly determined by
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