Neuron 63, 533–543 (2009)

The placebo effect is more hard-wired into the brain than previously thought.

For decades, scientists have known that sham treatments can relieve pain, and studies have identified natural opioid pathways as important players. But because the placebo effect seems to be linked to expectation, some have assumed that it occurs mainly through 'higher' brain structures associated with consciousness.

Falk Eippert at the University Medical Center Hamburg-Eppendorf in Germany and his team imaged the brains of volunteers given a sham ointment to relieve a mild burning pain. Half of them had been treated with naloxone, a chemical that blocks opioid signalling. The researchers found that placebo-related brain activity normally occurs in both the prefrontal cortex and more hard-wired areas, such as the amygdala, hypothalamus and parts of the brainstem.