Well I think if there are particles in the brain with certain velocities etc etc, I think they do change frequently.. For example. My cat walks in, sometimes I chose to play with it for a bit and sometimes I don't, Everything happens in our life weather it is bad weather, bad sleep or just a bad day. We think differently and we chose things differently.. So I don't think our brains could be mapped out if technology did ever reach that stage, I can see what point you're trying to give but I think that we have control over our life... not fully but some. But that's just my opinion.
So what I say is, we do have SOME control of our brain but not full control.