Table 8.

Parameters, their roles, and values in the numeric simulations of the hippocampal circuit.

Parameter	Role	Values
dt	simulation time step	1 ms
t +	time, input on	200 ms
t −	time, input off	100 ms
NE	total excitatory cells, each region	3,000
NI	total inhibitory cells, each region	$\frac{1}{5}\times N_E$
N 0̸	total cells receiving no input	$\frac{1}{6}\times (N_E+N_I)$
a	proportion of cells in each region deleted, atrophy	0.10 to 0.50 by 0.10
NS	max synapses from any cell i to any other cell j	35
τ α	membrane time constant	5 ms
V 0	resting value, membrane potential	5 mV
Vmax	maximum value, membrane potential (spike)	25 mV
Vmin	minimum value, membrane potential	1 mV
γ	spiking threshold	20 mV
λ	asymptotic inter-spike (waiting) time	100 ms
β	slope, spike-rate adaptation function	200
Jij, i, j ∈ E	mean synaptic efficiency, excit./excit. connections	0.20
Jij, i ∈ E, j ∈ I	mean synaptic efficiency, inhib./excit. connections	0.30
Jij, i ∈ I, j ∈ E	mean synaptic efficiency, excit./inhib. connections	0.60
Jij, i, j ∈ I	mean synaptic efficiency, inhib./inhib. connections	1.00
σ(J)	standard deviation, synaptic efficiency (all cases)	0.10
s	sparseness parameter, synaptic efficiencies	0.25
δ i,j	transmission delay between cells	1 ms within a given region 1 ms between EC and DG 2 ms between EC and CA3, CA1
$I_i^{\mathrm{ext}}$	mean external input	20
$\sigma \left(I_i^{\mathrm{ext}}\right)$	standard deviation, external input	$\frac{1}{4}\times I_i^{\mathrm{ext}}$
γL, γH	criterion number of output spikes, low and high load	1000, 2000
NR	number of replications at each level	5,000