Look at this programme summary of a radio documentary entitled, 'God on the Brain'. It explores the relatively new field of 'neurotheology': a study of the hypothesis that we are programmed to believe in God and that the condition known as temporal lobe epilepsy (TLE) could unlock the evidence to prove the truth of an individual's claims to know that God exists. If you check the 'Questions and answers' link, you'll also get a bibliography (useful aren't they!) and other web links to follow up your researches. You should especially look at the 2003 BBC Reith Lectures entitled 'The Emerging Mind' by Vilayanur S. Ramachandran, Director of the Centre for Brain and Cognition at the University of California (San Diego).