Figure 2. Repetitive firing in the AFHN model.
(A) Simulated 
traces for 
and different values for 
. The dashed lines indicate 
. (B) Phase-plane portrait for variable 
and 
. In each panel, the 
-nullcline (green) is shown for 3 values of 
. The 
-nullcline (blue) is independent of 
and 
. (C) 
-
parameter space, denoting regions of rest, repetitive firing, and block. The limit cycle lower and upper limits (
, Eq. 6 ) and rheobase (
, Eq. 9 ) as functions of 
. (D) Frequency and amplitude of action potentials, as functions of 
and 
.