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
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
Hypothesis: placebos create expectation of pain relief, which inhibits activity in pain processing areas
Participants: n= 23 Procedure: - Applied cream to forearm and told them cream was either an analgesic or control - 1 second cue was “Get Ready” seconds of anticipation - 20 seconds of heat - 4 seconds of rest - 4 seconds to rate intensity seconds of rest
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
DLPFC activation correlated with activation in the periaqueductal grey area during anticipation of pain in placebo condition compared to control condition
There was reduced activity in pain processing areas, predominantly in the late heat period (insula & thalamus), in the placebo condition compared to control condition
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
Future Direction: Further examine the role of the DLPFC in the placebo effect (opioid release vs. attention)
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)
Questions?