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
[27] and are identical to those parameters used in
our short-range orientation selectivity model
[38].
