The neural matrix of pain processing and placebo analgesia: Evidence from functional imaging

Recent functional imaging studies in humans have given us unprecedented opportunities to define the neuroanatomical basis for the placebo effect. Though these studies have largely been conducted in the field of pain and analgesia, the findings could well provide models for more general placebo effects in other clinical situations. Key regions that mediate the placebo effect include prefrontal cortices, anterior cingulate cortex (ACC) and brainstem structures, whereas the specific analgesic effects produced subsequent to a placebo response are mediated by a decreased activation in key pain processing brain regions, similar to that seen via pharmacological means. These new methods provide powerful tools with which to study the placebo response in pain and other diseases as they allow correlations to be made between cognitive manipulations and behavioral outcomes with changes in functionally defined neuroanatomical brain regions. Researchers are harnessing these methods to construct generalized models for the placebo effect that can be tested beyond the field of pain and analgesia. © 2005 American Headache Society and Blackwell Publishing