Roll your own mouse brain

Silicon Brain: 1,000,000 ARM cores - Computerphile
We have two problems with modeling the human brain. One is how a neuron works, and the other is how neurons are connected together. Modeling the impulses in single neuron might be fairly simple, if we knew how they worked. I suppose some people have some idea. How a complete neuron works is another matter entirely. It's a complete cell after all, with all the cellular machinery that implies. Using a living cell to perform the functions of a neuron is comparable to the using the city of Manhattan to support an adding machine.

APT Advanced Processor Technologies Research Group

     Connecting up the neurons is another matter. When we layout electrical circuits, we do it in a plane. We might have several layers, but you can basically draw it on a sheet of paper. This allows us to build them using simple techniques. Neurons in brains are connected in three dimensions. Some of these connections are to nearby cells, some are to cells a little farther away, and some are to cells on the other side of the world, figuratively speaking. You can't connect every cell to every other cell. You might be able to that with a dozen cells, but not with a zillion. So you have to pick and choose how you are going to connect your neurons. The toroid map they are using here lets you get some 3-D connections without making it impossible to build using conventional construction techniques.

Via Iaman.