The FitzHugh-Nagumo model. Speed variation of travelling waves

Excitation cI(t) with period T at the left border is added
to the system
∂_{t }u = DΔu + F(u, v) = DΔu +
u(1 - u)(u - a) - v + c I(t)δ(x),
∂_{t }v = H(u, v) = ε (bu - v),
I(t) ~ [cos(πt/T)]^{500},
_{-δ }∫^{ δ}I(t)dt = 1. Below you can see that travelling wave speed depend on recovery state.
The first impulse is the fastest. Next impulses are slower because v > 0
for them.
a
b
ε
Δt
Δx
D
T
c

delay
Ymin
Ymax
it
fps
Heart rhythmsupdated 3 Dec 2011