I have a friend who wants to study something applied to neurosciences. He is going to begin his grad studies in mathematics.
He asked me which areas of mathematics could be applied to neurosciences. 
Since I don't know the answer, I thought mathoverflow would be the right place to ask.
I mean, there are many areas of mathematics that could be applied to neurosciences. But the question is the following: which are the fields that have already been applied to neurosciences? Are there areas related to dynamical systems, stochastic process, probability, topology, analysis, PDE or algebra applied to neurosciences?
Articles are welcome. 


Thank you in advance



Which fields could be applied to neurosciences?
My wife is a neuroscientist. I can tell you what she uses:


$\bullet$ a LOT of statistics.  

$\bullet$ signal processing (such as wavelet transform).  

$\bullet$ some baysian probability theory.


