From The New York Times:
Hypnosis, with its long and checkered history in medicine and entertainment, is receiving some new respect from neuroscientists. Recent brain studies of people who are susceptible to suggestion indicate that when they act on the suggestions their brains show profound changes in how they process information. The suggestions, researchers report, literally change what people see, hear, feel and believe to be true.
Brain scans show that the control mechanisms for deciding what to do in the face of conflict become uncoupled when people are hypnotized.