I'm not saying the things we know are wrong. Unless we're missing something big, the nervous system is the way that animals process information. I'm just saying that there may be processes in the brain that influence this processing that make it unlike a neural network. For example, at least half of the brain is composed of glial cells which are responsible for upkeep. These cells interact directly with the neurons in multiple ways, such as myelinating axons to increase the speed of action potentials and clearing neurotransmitter molecules from synapses. While we know the basic functions of these cells, it is likely that there are some intricate ways in which they affect the brain's processes. In addition, there are many things that take place in the soma of the neuron that affect whether or not the neuron will have an action potential that we don't fully understand. Finally, neurons regularly move their synapses. This is something which we do not see in neural networks (at least none that I have seen) and is also something which we as yet don't understand. My point is that the brain is a very complex machine that we don't understand enough about to definitively say that it is equivalent in function to a neural network. It might be, but we just don't know.