Epilepsy is one of the most common brain diseases [1].
Several approaches are used to model it e.g. dynamical systems
[1] and networks [2]. In [2] a network is given or a 3-node graph
one represents low (unexcited) cells(L). The second represents
medium (M) and the third represent high (excited) cells (H). Here
this system is approximated by the dynamical system:
(1)
where a, b, c, d are positive constants. The coexistence solution
is
(2)
It exists if b/a < 1 and bd > c (3) and is locally asymptotically
stable if
(4)
The model (1) can be reduced to a 2-species model as follows:
(5)
and coexistence solution is:
(6)
And is stable if 2L > 1 (7) Healthy state exists if H << L . Now we
introduce the drug resistant type in epilepsy [3]. The populations
are low L, susceptible high Hs and resistant high Hr. The model is
(8)
The coexistence solution is
In the physically acceptable case Hr << L hence (c /d ) << 1, the
coexistence solution is locally asymptotically stable.