The theory was first proposed a few years ago by the German researcher Heiko Braak, M.D. He and his colleagues examined the autopsied brains of people who had died with Parkinson’s and found that alpha-synuclein protein accumulated in areas other than the substantia nigra. These areas, including the pons and the medulla in the brainstem, control body functions such as digestion, heartbeat and the regulation of sleep. His team also found widespread deposits of alpha-synuclein in nerve cells in the gut.