Table 1.

Biophysical simulation parameters

Parameter	Value
Rm	10 kΩcm2
Ra	200 Ωcm
Cm	1.0 μF/cm2
Vrest	−70 mV
Compartments	615
Somatic $\overline{g}$Na,$\overline{g}$DR	0.20, 0.12 S/cm2
Dendritic $\overline{g}$Na,$\overline{g}$DR	0.05, 0.03 S/cm2
Input frequency	0–100 Hz
$\overline{g}$AMPA	0.105–1.15 nS
τAMPA (on, off)	0.5 msec, 3 msec
$\overline{g}$NMDA	0.105–1.15 nS
τNMDA (on, off)	0.5 msec, 50 msec
Esyn	0 mV

Details of HH channel implementation are given elsewhere (Mel, 1993); original HH channel implementation adapted from Bernander et al. (1991). So that local EPSP size was held approximately constant across the dendritic arbor, peak synaptic conductance at dendritic locationx was approximately scaled to the local input resistance (inversely), given by $\overline{g}$_syn (x) = c/R̃_in (x), wherec was a constant, and R̃_in(x) = max (R_in (x), 200mΩ). Input resistance R_in(x) was measured for a passive cell. Thus$\overline{g}$_syn was identical for all dendritic sites with input resistance below 200 mΩ and was given by the larger conductance value shown; roughly 50% of the tree fell within a factor of 2 of this value. Peak conductances at the finest distal tips were smaller by roughly a factor of 10 (smaller number shown). Somatic input resistance was near 24 mΩ. Both AMPA- and NMDA-type synaptic conductances were modeled using the kinetic scheme of Destexhe et al. (1994); synaptic activation and inactivation time constants are shown for each. NMODL files used in the NEURON simulations are available for public download at http://lnc.usc.edu.