I am new to Theano, and I try to implement a numerical integrator of a reaction-diffusion system - [FitzHugh–Nagumo model](https://en.wikipedia.org/wiki/FitzHugh%E2%80%93Nagumo_model) of this version:

[![enter image description here](https://i.stack.imgur.com/OuQSG.jpg)](https://i.stack.imgur.com/OuQSG.jpg)

[![enter image description here](https://i.stack.imgur.com/KTKyV.jpg)](https://i.stack.imgur.com/KTKyV.jpg)

For now my expressions are:

```
import theano as th
import theano.tensor as T

u = T.dmatrix('u')
v = T.dmatrix('v')
e = T.dscalar('e')
a0 = T.dscalar('a0')
a1 = T.dscalar('a1')

dudt = u - u**3 -v
dvdt = e*(u - a1*v - a0)

```

So I haven't implemented the finite-differences [laplacian operator](https://en.wikipedia.org/wiki/Discrete_Laplace_operator#Finite_Differences) yet. My question is whether there is a smart way of doing it in Theano?