Excitatory and inhibitory cortical neurons were modeled separately using experimentally reported input resistances, membrane time constants, and firing characteristics of regular-spiking (RS) and fast-spiking (FS) neurons [9,27] Each cortical neuron was modeled as a single voltage compartment in which the membrane potential, , was given by:
where the synaptic conductances generated at each post-synaptic cell i by the spiking of each pre-synaptic cell j were given by:
and describe the delay and maximal conductance change produced for the synapse between cell j and cell i (see below). Spike-evoked conductance changes reached their maximal values at . represented the time of each spike (described by the set ) of pre-synaptic cell j. -mediated spike dynamics were replaced by a time-varying firing threshold. When the membrane potential exceeded threshold, a spike was recorded, the spike threshold was elevated, and a hyperpolarizing conductance was activated. Baseline spike threshold value was -55 mV. Cellular parameters were chosen to provide approximate fits to experimental frequency vs. current plots for cortical neurons  and are identical to those parameters used in our short-range orientation selectivity model .