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How the number of learning trials affects placebo and nocebo responses

Explore how the number of learning trials influences placebo and nocebo effects in pain management. Understanding cognitive factors and brain activity affecting responses.

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How the number of learning trials affects placebo and nocebo responses

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  1. How the number of learning trials affects placebo and nocebo responses LuanaColloca, PredragPetrovic, Tor D. Wager, Martin Ingvar, Fabrizio Benedetti

  2. Terms • Placebo - is a sham or simulated medical intervention that can produce a (perceived or actual) improvement • Nocebo – unpleasant response or reaction caused by a placebo drug or condition.

  3. Review! • http://www.youtube.com/watch?v=n8y04SrkEZU&feature=related

  4. Analgesic Pathway

  5. Placebo analgesia • Some placebo analgesia blocked by naloxone • Placebo affect = opioid modulated pathway • ACC may control placebo response • ACC activity increased by acute pain, opioid analgesia, and placebo analgesia • ACC  PAG

  6. ACC Nociceptive and Analgesic Effects

  7. Expectation and Placebo Analgesia

  8. Expectation and Placebo Analgesia

  9. Factors Influencing Placebo • Cognitive Factors • Expectation of pain relief trigger opioids in CNS • Classical Conditioning • Associations between active analgesics, pain relief, and therapeutic surroundings • Responders and Non-responders

  10. Materials • Electric stimulation to foot • randomized which foot • 100 microseconds • Yellow, green, or red light before shock

  11. Methods • Group 1: one session of conditioning • Group 2: four sessions of conditioning • Both groups: • Non-painful stimuli test • Painful stimuli test

  12. Test Types • Non-painful • Intensity of stimulation above Aβ fiber threshold but below nociceptive Aδ and C fiber threshold • Painful • Above nociceptive Aδ and C fiber threshold levels

  13. VAS Scoring • Subjects scored perception and pain (0-10 VAS) • T and t levels prior to testing • Pain rated after conditioning and test

  14. Testing Procedure

  15. Results (group 1)

  16. Results (group 1)

  17. Results (group 2)

  18. Results (group 2)

  19. Placebo/Nocebo relationship

  20. Placebo/Nocebo relationship

  21. Placebo/Nocebo relationship

  22. Average VAS Response

  23. Results Summery • Short conditioning period • No lasting effects for non-painful condition • Only painful nocebo effect endured • Long conditioning period • Both placebo and nocebo effects endured

  24. Discussion • Conditioning is needed for placebo and nocebo effects • Both conscious and subconscious learning shape behavior • Past experience with pain relief effect the efficacy of treatment • Clinical usage of placebo and avoidance of nocebo

  25. Unrelated… • http://www.youtube.com/watch?v=qIoG4PlEPtY

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