Placebo effect traced to region of brain

ANN ARBOR, Mich., Feb. 19 (UPI) -- One part of the brain may fool the rest of the body into responding to inactive drugs or placebos, U.S. neurologists reported Thursday.

The prefrontal cortex is the area of the brain most active in the placebo response, the team from the University of Michigan and Princeton reported in two related studies. Both used functional magnetic resonance imaging to look at the brain.

Subjects were given mild pain stimuli and then a cream they were told would relieve the pain. When subjects applied the cream to their arm, they rated the pain as less intense -- and the pain circuits in their brain showed less activity, the study said.

The researchers said the prefrontal cortex responded first, in expectation of pain relief, and in turn triggered reactions in pain-sensing areas of the brain, such as the thalamus and somatosensory cortex.

Doctors have long recognized the power of a placebo to make patients feel better. The new studies provide the first scans documenting the changes induced by a placebo in the brain's pain pathways.