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bioRxiv · 10.64898/2026.10.07.757355

Selective Nerve Block of A- or C-Afferents Confirms Dual Role in Touch Pleasantness but Not Touch-Pain Modulation

Albinni, B.·Crankshaw, L. N.·Jones, E.·Alasha, V.·Zimmerman, M.·Schuster, N.·Said, E.·Strigo, I.·Case, L. K.
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Abstract

Gentle and deep pressure are distinct types of touch that often elicit pleasant sensations and modulate pain. Although touch pleasantness has traditionally been attributed to unmyelinated C-tactile afferents, growing evidence suggests an important contribution of myelinated A-fibers. However, the relative role of A- and C-fibers in touch-evoked pleasantness and pain modulation remains unclear. To test the role of A- and C-fibers in touch pleasantness, healthy adults underwent selective peripheral nerve block of the superficial radial nerve to preferentially impair either A- or C-fiber function. Touch pleasantness of brushing (Study 1; N = 24) or deep pressure (Study 2; N = 24) and touch-induced modulation of heat pain were assessed before and after the nerve block. Both nerve blocks significantly reduced the perceived pleasantness of both gentle brushing and deep pressure, supporting a substantial contribution of myelinated A-fibers and well as unmyelinated C-fibers (presumably C-tactile fibers) to affective touch. In addition, block of A-fibers did not diminish touch-induced modulation of experimental heat pain, suggesting a particular pain-inhibiting role for C-tactile fibers. These findings supply causal evidence in healthy adults that myelinated A-fibers are highly involved in touch pleasantness-alongside C-tactile fibers-but are not involved in touch-induced pain relief.

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Albinni, B., Crankshaw, L. N., Jones, E., Alasha, V., Zimmerman, M., Schuster, N., Said, E., Strigo, I., Case, L. K.. 2026-10-14. Selective Nerve Block of A- or C-Afferents Confirms Dual Role in Touch Pleasantness but Not Touch-Pain Modulation. https://doi.org/10.64898/2026.10.07.757355

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