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Placebo analgesia enhances descending pain-related effective connectivity: a dynamic causal modeling study of endogenous pain modulation
- Source :
- The journal of pain. 16(8)
- Publication Year :
- 2015
-
Abstract
- The use of placebo to reduce pain is well documented; however, knowledge of the neural mechanisms underlying placebo analgesia remains incomplete. This study used functional magnetic resonance imaging data from 30 healthy individuals and dynamic causal modeling to investigate changes in effective connectivity associated with the placebo analgesic response. Before scanning, participants were conditioned to expect less thermal pain at 2 of 4 sites on their feet. Visual analog scale pain ratings revealed a significant but small difference between the baseline and placebo sites (mean difference = 6.63, t(29) = 3.91, P ≤ .001, d = .97), confirming an analgesic effect. However, no significant differences in the magnitude of brain activation between conditions were observed via traditional random effects general linear modeling. Dynamic causal modeling was then used to investigate changes in effective connectivity during placebo analgesia. The results indicate that during placebo analgesia but not baseline condition, couplings between brain regions, including those involved in cognitive processes (eg, attention, expectation, evaluation), were significantly enhanced. Specifically, a significantly consistent decrease in the dorsolateral prefrontal cortex → periaqueductal gray coupling was found. These findings highlight the differences between pain processing and modulation at the network level. Moreover, our results suggest that small placebo effects may be better characterized via changes in the temporal dynamics among pain modulatory regions than only via changes in the magnitude of blood oxygenation level dependent activation. Further application of nuanced analytical approaches that are sensitive to temporal dynamics of pain-related processes such as dynamic causal modeling are necessary to better understand the neural mechanisms underlying pain processing in patient populations. Perspective Changes in effective connectivity among pain-related brain regions may be more sensitive detectors of the neural representation of small placebo effects than are changes in the magnitude of brain activation. Knowledge of these mechanisms highlights the importance of integrated neural networks in the understanding of pain modulation.
- Subjects :
- Adult
Male
Models, Anatomic
Visual analogue scale
Analgesic
Pain
Placebo
Periaqueductal gray
Efferent Pathways
Article
Young Adult
Image Processing, Computer-Assisted
Psychophysics
Medicine
Humans
Causal model
Pain Measurement
medicine.diagnostic_test
business.industry
Temperature
Brain
Cognition
Placebo Effect
Magnetic Resonance Imaging
Dorsolateral prefrontal cortex
Oxygen
Anesthesiology and Pain Medicine
medicine.anatomical_structure
Neurology
Nonlinear Dynamics
Female
Neurology (clinical)
business
Functional magnetic resonance imaging
Neuroscience
Subjects
Details
- ISSN :
- 15288447
- Volume :
- 16
- Issue :
- 8
- Database :
- OpenAIRE
- Journal :
- The journal of pain
- Accession number :
- edsair.doi.dedup.....41e2eeefc5aa9ea9b687e8209d0a0663