The brain in Creatures is a very complex thing built of about 900 neurons and many thousand dendrites.
In Creatures a neuron is a place where you can store a number value. Most neurons loose the saved value over time, but some does that faster than others.
Dendrites are the connection between different neurons. Dendrites work unidirectional, so the value of neuron 1 may influence the value of neuron 2, but not vice versa. Dendrites may have different behaviours and some just transfer the value of one neuron to another one, while others may negate the value or do even more complex work.
Creatures 3 introduces a new neuronal processing system, called "State Value Rules" or SV Rules.
In Creatures 3 and Docking Station each neuron and dendrite is a fully functional register machine. That means that you have several registers (places where you can store something) and one special working register. The most important commands on a register machine are LOAD, which loads a value into the working register and STORE, which stores a value from it into one of the other registers.
Operations like ADD always uses the value of the working register. Look at the following example, which adds the value from register 1 to the one of register 0 and stores the new value in register 2.
- LOAD 0
- ADD 1
- STORE 2
However, the SV Rules system adds some extensions to the usual register machine, like access to the cretures' chemical system or to its reception. Take your favourite genetics editor and take a look into one of the Brain Lobe or Brain Tract genes to get a full (?) list of supported operations.