The direction and magnitude of conditioned pain modulation is dependent on test stimulus intensity in healthy participants but not in those with fibromyalgia
Bibliographic record
Abstract
Conditioned pain modulation (CPM) is a psychophysical phenomenon considered to be a measure of endogenous descending pain modulatory mechanisms. Previous rodent data from our lab demonstrated that test stimulus intensity affects CPM's direction, with higher-intensity stimuli leading to hypoalgesia (i.e., CPM) and lower-intensity stimuli leading to hyperalgesia (i.e., "anti-CPM"). Our primary aim was to see if we could replicate these findings in humans. Because deficits in CPM suggest low capacity to inhibit pain-a risk factor for chronic pain-the secondary aim of this study was to see how this "anti-CPM" phenomenon presented itself in chronic pain patients with fibromyalgia. Healthy controls (n=51) and participants with fibromyalgia (n=39) underwent an individual heat pain threshold assessment, followed by a single CPM trial, at -1, +1, or +3 °C below/above their threshold. The CPM trial consisted of two baseline sub/suprathreshold heat pain stimulations (the test stimulus), a 30-s cold pressor test (4 °C) as a conditioning stimulus, and a final heat pain stimulation at the same temperature, with pain ratings provided throughout. Healthy controls displayed statistically significant CPM analgesia at +3 °C, no change at +1 °C, and hyperalgesia (anti-CPM) at -1 °C. Further analyses revealed that subjective intensity of the test stimulus determined the direction and magnitude of CPM. We observed no significant evidence for either analgesic CPM or anti-CPM in participants with fibromyalgia, suggesting that the mechanism(s) subserving both phenomena are dysfunctional in them. PERSPECTIVE: Similar to previous work in rodents, we show here that the use of lower-intensity test stimuli leads to hyperalgesic, instead of analgesic, conditioned pain modulation (CPM). Neither form of CPM was observed in participants with fibromyalgia.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".