Table 1.

Summary of physical and lumped parameters in the computational model.

PHYSICAL QUANTITIES
Symbol	Description
Vth	Firing threshold of afferent fibers
c0	Conductivity of the superficial tissue under skin
c1	Electrical resistance of nerve endings per unit length
C1	Membrane capacitance of nerve endings
G1	Membrane conductance of nerve endings
ρ	Surface density of nerve endings
h	Distance between nerve endings and the electrode
ḡ	Maximal conductance of the AMPA-mediated synapse
K	Potential gradient between the postsynaptic potential and the AMPA-reversal potential
C2	Membrane capacitance of secondary neurons
G2	Membrane conductance of secondary neurons
αh	Activation threshold of secondary neurons
σh	Slope parameter of the activation of secondary neurons
l	Number of secondary neurons
λh	Maximal firing rate of single secondary neurons
LUMPED PARAMETERS
Symbol	Description		Expression		Reference value
α1	Activation threshold of afferent fibers		$\left(4\pi c_0{c}_1{G}_1{V}_{th}\right)h^2$		0.125 mA
τ1	Time constant of afferent fibers		$C_1{G}_1^{-1}$		0.2 ms
τ2	Time constant of secondary neurons		$C_2{G}_2^{-1}$		45 ms
αL	Activation threshold of secondary neurons		$\left(\frac{8}{3}\pi c_0{c}_1{G}_1{G}_2{V}_{th}\right){\alpha }_h{(\rho ḡK)}^{-1}$		0.00417 A/s
σL	Slope parameter of firing rate function		$\left(\frac{8}{3}\pi c_0{c}_1{G}_1{G}_2{V}_{th}\right){\sigma }_h{(\rho ḡK)}^{-1}$		8.33 × 10−5 A/s
λL	The maximal population firing rate		lλh		0.01 kHz