One way of figuring out what the brain is, is to ask what purposes the brain fulfils for evolution. Apart from high speed control (low speed control can be done by other means than neurons), you can also view the brain as an enabler for speeding evolution, by adapting to body changes. Imagine if evolution had to wait for a mutation in the sensing/control system as well as a change in body plan before it make a body modification. Eyes would have a hard time coming into existence as there would be nothing to process the information they provided in a useful fashion.

So you can see the brain as a system to figure out what body it is in, and what it should be doing and how it should be processing information based on feedback of usefulness of its actions (which don't change much in evolutionary time, such as food, sex, status and children*). Evolutionary usefulness being indicated by pleasure and other such signals. Yet we are not constrained to try and maximize these signals. Just that behaviours and goal seeking parts of the mind that happen to do things that produce these signals get reinforced. We can choose to avoid getting usefulness signals, as we do when we chose not to take addictive drugs.

I'm not sure if you get any closer to figuring out the consciousness problem. But it might be a start.

• The evolutionary nature of the brain is shown perhaps most by how we find baby mammals cute and we wish to take care of them. The part of the brain that deals with kids doesn't know what type of body it is going to end up in so is indiscriminate in making young-looking mammals cute.