In two related studies at the Ann Arbor Veterans Affairs (VA) Health Care System, University of Michigan and Princeton University, researchers used functional magnetic resonance imaging (fMRI) to map changes in blood flow in the brains of volunteers. The volunteers were subjected to harmless but occasionally painful electric shocks or heat. When they believed an anti-pain cream had been applied to their arm, they rated the pain as less intense--and the pain circuits in their brain showed less activity.
Doctors have long recognized the power of placebo to make patients feel better. But scientists are unsure why it works, and whether nerve pathways are actually affected. The new studies provide the first scans documenting the changes induced by placebo in the brain's pain pathways.
"We've shown what the old family doctor knew very well--that his interaction with the patient made a great difference in the effectiveness of whatever treatment he was giving," said one of the researchers, Kenneth L. Casey, MD, who has studied pain for three decades. Casey is a neurology consultant for VA and a professor at the University of Michigan. Lead author was Tor D. Wager, MD, a graduate student at the University of Michigan when the research was conducted.
Researchers have performed brain experiments with fMRI since the early 1990s. It uses the technology of MRI--radio waves and a strong magnetic field--to show regions of the brain where blood vessels are widening, extra oxygen is being delivered, or other chemical changes are occurring. These are signs that an area of the brain is busy at work. By taking fMRI images as patients perform different tasks, researchers learn which areas of the brain
Contact: Bonnie Johnson
VA Research Communications Service