Opioid and placebo analgesia share the same network

Abstract

The relationship between the endogenous opioid system and placebo analgesia has fascinated the research community for decades. Using functional imaging methods, it is now possible to study the underlying opioid and placebo processes in the brain. Such studies have shown overlapping activity in the anterior cingulate cortex (ACC) and the insula stretching into the orbitofrontal cortex. Because the ACC is involved in top-down attentional regulation, this region may mediate the interaction between higher cognitive processes and the endogenous opioid network. Moreover, data also indicate that the ACC may exert its modulation through the brainstem opioid network. The orbitofrontal cortex also shows placebo-dependent activation, but it does not have similar access to the opioid network. Thus, this region may be involved in other aspects of the placebo response such as processing treatment expectations.