Simplified models of correlated synaptic background activity in neocortical pyramidal neurons.
Alain Destexhe and Michael Rudolph

Society for Neuroscience Abstracts 26: 1623, 2000.

Neocortical neurons may have different electrophysiological properties when subject to the intense synaptic background activity present in intact networks in vivo. We have recently proposed models of cortical neurons in active states in vivo, which can be used to investigate these properties. However, these models require to simulate thousands of excitatory and inhibitory synapses, which practically rules out the use of these models in network simulations. We propose here a simplified model of pyramidal neurons in vivo, which has qualitatively equivalent behavior as detailed biophysical models. In the detailed model, synaptic background activity was represented by thousands of synapses releasing randomly in a correlated manner, producing the conductance and Vm fluctuations recorded intracellularly in vivo. In the simplified model, these synapses were collapsed into a point-conductance model with only two stochastic variables. The simplified model had electrophysiological properties consistent with intracellular measurements in pyramidal neurons in vivo;: input resistance, average Vm (around -65 mV), and high-amplitude Vm fluctuations. In addition, the simplified model reproduced highly variable spontaneous discharges and enhanced responsiveness similar to that found in more complex models (see companion abstract). We conclude that point-conductance models can capture the most salient electrophysiological properties of neocortical pyramidal neurons in the presence of synaptic background activity in vivo, and should be useful to represent synaptic background activity in various situations.

Supported by: MRC and NIH