I was interested in big unknowns, and the brain is one of the biggest, so building tools that allow us to regard the brain as a big electrical circuit appealed to me.
It's not even known how many kinds of cells there are in the brain. If you were looking for a periodic table of the brain, there is no such thing. I really like to think of the brain as a computer.
What I'm really interested in is this idea of a 'brain co-processor' - a device that can record from, and deliver information to, so many points in the brain, with a computational infrastructure in between - a computer that can process the information and compute exactly what needs to be restored.