Actually this is incorrect according to the Fathers. The brain is the seat of the intellect, the reasoning power of the soul, but it is not where the spiritual nature of the soul resides. If anything we would have to locate the soul in the heart along with the incensive aspect of the soul - but I'm not sure that any physical organ can be identified as the "seat" of the spirit.
Fr David Moser
With all due respect to these fathers, I probably have a little more experience with the relationship between the soul and brain owing to a number of tests required prior to a right temporal lobectomy. Admittedly I'm only coming at this from the personal experience of having each side of my brain put to sleep to test memory and locate where speech is centered, but in that process at one point I found myself thinking and processing information faster than I ever had (again, my perception of events and I was off my epilepsy medications for the first time in 13 years) and this was happening when my brain was in a chemically induced snooze. If my brain, the seat of the intellect, was for all intents and purposes switched off (the higher cognitive functions, at least), where did I find the means to analyse the situation? The person administering the Wada test said that a lot of folks mention heightened awareness but he wouldn't hazard a guess as to why. I have my own theories, which involve the soul's ability to function independent from its body.