Welcome bioengineer. I suggest you do a google on what Ramachandran has been researching concerning religious beliefs and the brain. I would also recommend Michael Persingers book Neuropsychological Bases of God Beliefs. The research,as you probably know by now, indicates that the Temporal Lobes are involved in religious and hyper-religious thought.
How different the JWs would be than the rest of the population is hard to say. Their religion is more intellectual compared to, let's say pentecostals. That is likely to involve different parts of the brain but I believe that is a secondary issue. The primary cause is still the Temporal Lobes and people with brain damage there tend to display a certain range of symptoms including hyperreligiosity, hypergraphia, altered sexuality (not all necessarily at the same time).
It's a fascinating subject as it shows that it is our material brains that determine who we are.