Does the placebo [effect] change the way a person constructs the experience of pain, or is it changing the way a person thinks about it after the fact? Is the person really feeling less pain?
[Researchers at Dartmouth college] were able to confidently localize placebo effects to specific zones of the brain, including the thalamus and the basal ganglia. The thalamus serves as a gateway for sights and sounds and all kinds of sensory motor input. It has lots of different nuclei, which act like processing stations for different kinds of sensory input. The results showed that parts of the thalamus that are most important for pain sensation were most strongly affected by the placebo.
In addition, parts of the somatosensory cortex that are integral to the early processing of painful experiences were also affected. The placebo effect also impacted the basal ganglia, which are important for motivation and connecting pain and other experiences to action. “The placebo can affect what you do with the pain and how it motivates you, which could be a larger part of what’s happening here,” said [researcher Tor] Wager. “It’s changing the circuitry that’s important for motivation.”