Selective Laser Stimulation of Aδ- or C-Fibers Through Application of a Spatial Filter: A Study in Healthy Volunteers
Bibliographic record
Abstract
Background: Pain is perceived through different pathways involving thinly myelinated Aδ-fibers and unmyelinated C-fibers. Aδ-fibers are responsible for a quick, sharp pain, whereas C-fibers relate to a late-onset, burning sensation. Several studies suggest that it is essential to investigate nociceptive fibers separately and in relation to each other. The aim of this study was to selectively stimulate Aδ- and C-fibers using a 980-nm diode laser by varying the laser settings and the stimulated surface area in healthy subjects. Methods: Selective activation of Aδ- and C-fibers is possible using their distinctive physiological characteristics. We used the differences in heat activation threshold and surface density to selectively activate Aδ- and C-fibers. Stimuli from a 980-nm diode laser were applied to 44 healthy volunteers. Two different laser settings were applied for selective stimulation of Aδ-fibers (20 ms at 2.7 W) and C-fibers (50 ms at 0.8 W). A spatial titanium filter, containing 40 holes with varying diameters (0.4, 0.6, 1, and 2 mm), was used to apply the stimuli with varying surface areas. The test subjects received 80 stimuli in total and were asked to press a button when the stimulation was felt. Reaction times between 300 and 650 ms indicate Aδ-fiber activation, whereas reaction times between 650 and 2,000 ms indicate C-fiber activation. Results: First, the usage of response time to discriminate between Aδ- and C-fiber activation was validated. Then, the combined use of the two different stimulation protocols and a spatial filter turned out to be effective to achieve different probabilities of stimulating Aδ- or C-fibers. With the Aδ-protocol and a grid diameter of 2 mm, an Aδ:C response ratio of 1.17:1 was reached, and with the C-protocol and a grid diameter of 0.4 mm, the Aδ:C ratio was 0.05:1. Conclusions: Our results indicate that cutaneous heat stimuli applied with a 980-nm diode laser, using a specific stimulation paradigm and a spatial filter, allow us to selectively activate Aδ- and C-fibers. These findings could serve as a basis for clinical investigation of different involvements of Aδ- and C-fibers in patients suffering from small fiber neuropathies. J Neurol Res. 2016;6(1):1-7 doi: http://dx.doi.org/10.14740/jnr361w
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| 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 | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".