Researchers at the University of Iowa Roy J. and Lucille A. Carver College of Medicine and the Technical University of Aachen, Germany, used functional magnetic resonance imaging (fMRI) to find out if hypnosis alters brain activity in a way that might explain pain reduction. The results are reported in the November-December 2004 issue of Regional Anesthesia and Pain Medicine.
The researchers found that volunteers under hypnosis experienced significant pain reduction in response to painful heat. They also had a distinctly different pattern of brain activity compared to when they were not hypnotized and experienced the painful heat. The changes in brain activity suggest that hypnosis somehow blocks the pain signal from getting to the parts of the brain that perceive pain.
"The major finding from our study, which used fMRI for the first time to investigate brain activity under hypnosis for pain suppression, is that we see reduced activity in areas of the pain network and increased activity in other areas of the brain under hypnosis," said Sebastian Schulz-Stubner, M.D., Ph.D., UI assistant professor (clinical) of anesthesia and first author of the study. "The increased activity might be specific for hypnosis or might be non-specific, but it definitely does something to reduce the pain signal input into the cortical structure."
The pain network functions like a relay system with an input pain signal from a peripheral nerve going to the spinal cord where the information is processed and passed on to the brain stem. From there the signal goes to the mid-brain region and finally into the cortical brain region that deals with conscious perception of external stimuli like pain.