From the BBC. What this article does not make clear is the amount of idealization involved. Neuronal interactions are so complicated at the chemical level, and there might be aspects which are not understood yet.
US researchers have simulated half a virtual mouse brain on a supercomputer. The scientists ran a "cortical simulator" that was as big and as complex as half of a mouse brain on the BlueGene L supercomputer. In other smaller simulations the researchers say they have seen characteristics of thought patterns observed in real mouse brains. Now the team is tuning the simulation to make it run faster and to make it more like a real mouse brain.