A recent article in scholarpedia by Prof. Bruce Knight:

Currently (2009) the Hartline-Ratliff model, of dynamics in the thousand- faceted retina of the horseshoe crab Limulus, presents the only example of a fully characterized and solved large neural network, in an actual living species, which yields accurate and insightful prediction of that network‘s response to fairly arbitrary stimuli. This is achieved with standard advanced methods of dynamical system analysis.

The rest can be found on this link: The Accurate Quantitative Solution of a Living Neural Network