. 2004 Jun 14;23(1):53–72. doi: 10.1002/hbm.20032

Table I.

Brain parameters for normal adults in the alert, eyes‐open state

Quantity	Symbol	Prior range	Range	Estimate	Unit
Corticocortical e axon
Rangea, b	r _e	50–200	89 ± 9	86	mm
Axonal velocity	υ_e	6–11	9.8 ± 1.2	10	m/s
Cortical damping ratea, b	γ_e = υ_e/r _e	30–220	116 ± 4	116	s⁻¹
Corticothalamic
Axonal velocity	V	4–11	4.5 ± 0.5	4.2	m/s
Loop distance	R	100–400	360 ± 40	360	mm
Loop delaya, b	t ₀ = R/V	9–100	85 ± 1	85	ms
Synaptodendritic
Decay timea, b	1/α	5–200	12 ± 2	12	ms
Rise timea, b	1/β	0.4–60	1.3 ± 0.3	1.3	ms
Maximum firing ratea	Q _max	100–1,000	220–500	340	s⁻¹
Firing thresholda	θ	10–25	10–17	13	mV
Threshold spreada	σ′	2–6	3.8 ± 0.2	3.8	mV
Threshold ratio	θ/σ′	1.7–12	3.4 ± 0.9	3.4	—
Firing rate
e Neurons	ϕ $_{e}^{(0)}$	16 ± 2	16 ± 2	16	s⁻¹
s Neurons	ϕ $_{s}^{(0)}$	16 ± 7	16 ± 7	16	s⁻¹
r Neurons	ϕ $_{r}^{(0)}$	24 ± 5	24 ± 5	24	s⁻¹
n Neurons	ϕ $_{n}^{(0)}$	16 ± 4	16 ± 4	16	s⁻¹
Resting firing rate	ϕ₀	4–18	7–18	11	s⁻¹
Sigmoid slope
For e neurons	ρ_e	1–10	3.5–5.0	4.2	(mV s)⁻¹
For s neurons	ρ_s	1–10	2.0–6.7	4.2	(mV s)⁻¹
For r neurons	ρ_r	1–10	5.0–7.6	6.3	(mV s)⁻¹
Afferent synapses
Per e neuron	N _e = N _ee + N _ei + N _es	(4–40) × 10³	(4–40) × 10³	1.2 × 10⁴	—
Per s neuron	N _s = N _se + N _sr + N _sn	1,000–8,000	1,000–8,000	2,100	—
Per r neuron	N _r = N _re + N _rs	1,000–8,000	1,000–8,000	3,400	—
e Synapses/e neuron	N _ee = (0.75–0.85)N _e	(3–34) × 10³	(3–34) × 10³	10⁴	—
i Synapses/e neuron	N _ei = (0.1–0.15)N _e	400–6,000	400–6,000	1,600	—
s Synapses/e neuron	N _es = (0.05–0.1)N _e	200–4,000	200–4,000	800	—
e Synapses/s neuron	N _se = (0.3–0.6)N _s	300–4,800	300–4,800	1,100	—
r Synapses/s neuron	N _sr = (0.2–0.4)N _s	200–3,200	200–3,200	550	—
n Synapses/s neuron	N _sn = (0.1–0.5)N _s	100–4,000	100–4,000	450	—
e Synapses/r neuron	N _re = (0.7–0.8)N _r	700–6,400	700–6,400	2,700	—
s Synapses/r neuron	N _rs = (0.2–0.3)N _r	200–2,400	200–2,400	700	—
Synapse strength
e Synapse on e neuron	s _ee	<10	0.03–0.7	0.15	μV s
i Synapse on e neuron	−s _ei	<10	0.3–6	1.3	μV s
s Synapse on e neuron	s _es	<10	0.05–5	0.5	μV s
e Synapse on s neuron	s _se	<10	0.04–6	0.5	μV s
r Synapse on s neuron	−s _sr	<10	0.06–10	0.8	μV s
n Synapse on s neuron	s _sn	<10	0.03–5	0.4	μV s
e Synapse on r neuron	s _re	<10	0.004–0.5	0.07	μV s
s Synapse on r neuron	s _rs	<10	0.003–0.3	0.05	μV s
Synaptic producta
ee	ν_ee = N _ee s _ee	0.3–340	1.6 ± 0.4	1.60	mV s
ei	−ν_ei = −N _ei s _ei	0.04–60	1.9 ± 0.5	1.90	mV s
es	ν_es = N _es s _es	0.02–40	0.2–1.0	0.39	mV s
se	ν_se = N _se s _se	0.03–48	0.2–2.0	0.60	mV s
sr	−ν_sr = −N _sr s _sr	0.02–32	0.2–2.8	0.45	mV s
sn	ν_sn = N _sn s _sn	0.01–40	0.1–0.5	0.15	mV s
re	ν_re = N _re s _re	0.07–64	0.03–0.3	0.15	mV s
rs	ν_rs = N _rs s _rs	0.02–24	0.007–0.06	0.03	mV s
Gain
ee b	G _ee	3–3,400	6.8 ± 0.2	6.8	—
ei b	−G _ei	0.4–600	8.1 ± 0.2	8.1	—
es	G _es	0.2–400	0.9–3.3	1.7	—
se	G _se	0.3–480	1.1–3.8	2.5	—
sr	−G _sr	0.2–320	1.2–5.5	1.9	—
sn	G _sn	0.7–1.0	0.7–1.0	0.8	—
re	G _re	0.7–640	0.25–1.3	1.0	—
rs	G _rs	0.2–240	0.06–0.28	0.19	—
Positive CT loopb	G _ese = G _es G _se	6 × 10⁻⁴–2,000	4.2 ± 0.2	4.2	—
Negative CT loopb	−G _esre = −G _es G _sr G _re	3 × 10⁻⁵–8 × 10⁴	3.1 ± 0.1	3.1	—
Intrathalamic loop	−G _srs = −G _sr G _rs	6 × 10⁻⁴–800	0.37 ± 0.05	0.37	—
Input path	G _esn = G _es G _sn	0.4–400	0.6–3.3	1.4	—
Spatial low‐pass wavenumber	k ₀	—	29 ± 9	29	m⁻¹
Spatial low‐pass wavenumber × r _e a, b	k ₀ r _e	—	2.5 ± 0.5	2.5	—

The first column gives a brief description of the parameter, with its symbol listed in the second. The third column gives the range currently obtainable without imposing model‐based constraints, while the fourth gives the range obtained here. The fifth column gives a self‐consistent nominal set of parameters. Units of each quantity given in the final column. Only quantities discussed in the present work are listed and concentrate on mean values; individuals will scatter within and around the ranges quoted.

Parameters required for the nonlinear version of the model.

Parameters required for the linear version of the model.

CT, corticothalamic.