CTRNN basics

This paper:

On the Dynamics of Small Continuous-Time Recurrent Neural Networks, Randall Beer

provides a very good analysis of the inner workings for CTRNNs. There is an example problem solved using this kind of neural network.

For more scientific approaches to CTRNNs, you can follow this research:

Approximation of Dynamical Systems by Continuous Time Recurrent Neural Networks, Ken-ichi Funahashi and Yuichi Nakamura

This study involves a lot of mathematical background for these networks and describes the way in which they can model dynamical systems. Containing theorems and proofs.