Neuroimaging resolution of the altered state hypothesis

A controversy in the field of hypnosis has centered on the question of whether there is a uniquely hypnotic state of consciousness and, if so, whether it is causally related to responsiveness to suggestion. Evidence from brain imaging studies has been used to support claims for various altered state hypotheses, without resolving the debate. The designs of many neuroimaging studies confound the induction of hypnosis with the suggestions that can be given in or out of hypnosis, thus rendering them incapable of resolving the controversy. Brain imaging studies that do not have this confound support the hypothesis that hypnotic inductions produce changes in brain activity, but also indicate that these changes are not required for the experience of hypnotic suggestions or their neural correlates. The data remain equivocal as to whether there is a causal relation between the changes in brain activity produced by hypnotic inductions and those produced by other suggestions. It also remains uncertain whether the changes in activation produced by hypnotic inductions reflect a uniquely hypnotic state as opposed to more mundane processes.