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  • Placebo improves pleasure and pain through opposite modulation of sensory processing.

Placebo improves pleasure and pain through opposite modulation of sensory processing.

Proceedings of the National Academy of Sciences of the United States of America (2013-10-16)
Dan-Mikael Ellingsen, Johan Wessberg, Marie Eikemo, Jaquette Liljencrantz, Tor Endestad, Håkan Olausson, Siri Leknes
ABSTRACT

Placebo analgesia is often conceptualized as a reward mechanism. However, by targeting only negative experiences, such as pain, placebo research may tell only half the story. We compared placebo improvement of painful touch (analgesia) with placebo improvement of pleasant touch (hyperhedonia) using functional MRI and a crossover design. Somatosensory processing was decreased during placebo analgesia and increased during placebo hyperhedonia. Both placebo responses were associated with similar patterns of activation increase in circuitry involved in emotion appraisal, including the pregenual anterior cingulate, medial orbitofrontal cortex, amygdala, accumbens, and midbrain structures. Importantly, placebo-induced coupling between the ventromedial prefrontal cortex and periaqueductal gray correlated with somatosensory decreases to painful touch and somatosensory increases to pleasant touch. These findings suggest that placebo analgesia and hyperhedonia are mediated by activation of shared emotion appraisal neurocircuitry, which down- or up-regulates early sensory processing, depending on whether the expectation is reduced pain or increased pleasure.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Oxytocin
Sigma-Aldrich
Oxytocin, lyophilized powder, ~15 IU/mg solid (Prepared from synthetic oxytocin)
Oxytocin, European Pharmacopoeia (EP) Reference Standard
Sigma-Aldrich
Oxytocin acetate salt hydrate, ≥97% (HPLC)