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Placebo-Induced Changes in fMRI in the Anticipation and Experience of Pain. Tor D.Wager , James R. Killing, Edward E. Smith, Alex Sokolik , Kenneth L. Casey, Richard J. Davidson, Stephen M. Kosslyn , Robert R. Rose & Jonathan D. Cohen . Presented by Javier Granados- Samayoa. Introductio n.
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Placebo-Induced Changes in fMRI in the Anticipation and Experience of Pain Tor D.Wager, James R. Killing, Edward E. Smith, Alex Sokolik, Kenneth L. Casey, Richard J. Davidson, Stephen M. Kosslyn, Robert R. Rose & Jonathan D. Cohen Presented by Javier Granados-Samayoa
Introduction • Pain can be modulated by attitudes and beliefs • Placebo Analgesia: reduction of pain through the belief that an inert treatment has analgesic properties • Some suggest the placebo effect can be attributed to response bias • An opioid antagonist reverses the placebo effect • Information processing mechanism not known
Introduction • Hypothesis: placebos create expectation of pain relief, which inhibits activity in pain processing areas
Methods • Participants: n= 23 • Procedure: - Applied cream to forearm and told them cream was either an analgesic or control - 1 second cue was “Get Ready” • 1-16 seconds of anticipation • 20 seconds of heat • 4 seconds of rest • 4 seconds to rate intensity • 40-50 seconds of rest
Results • Areas in the right and left dorsolateral prefrontal cortex (DLPFC) were more active in anticipation of pain for the placebo condition compared to control condition
Results • DLPFC activation correlated with activation in the periaqueductal grey area during anticipation of pain in placebo condition compared to control condition
Results • There was reduced activity in pain processing areas, predominantly in the late heat period (insula & thalamus), in the placebo condition compared to control condition
Discussion • PFC generates and maintains expectations about pain, which influence activity of pain processing areas • PFC activity triggers opioid release which inhibits afferent pain fibers • Late decreases in pain processing area activation may reflect cognitive reappraisal of pain, which may lead to reduced emotional significance and experience of pain
Discussion • Future Direction: Further examine the role of the DLPFC in the placebo effect (opioid release vs. attention)
Opinion • Strengths: - good control condition - experimental design allows for distinction between different pain periods - had different pain manipulations • Limitations: - cannot distinguish what the role of the PFC is in the placebo effect - did not use different placebo conditions can lead to different results (Blackwell, Bloomfield & Buncher, 1972)
Thank you. Questions?