A biochemist told me once that the fastest way for micoscopic parasites and bacteria to move was through all the nerves in the body. The nerves are like elevators for them because they are so small, he said. So that could perhaps mean that some of them potentially could move in just minutes from the colon to the brain or at least out in the nerve endings when they feel a threat coming like parasite herbs. Also the brain is a pretty safe place to be compared to other places in the body. Just a thought though. I don't believe it's very common to have them in the brain though, especially not if you are living without severe depressions or other mental problems.