Selective Nerve Block of A- or C-Afferents Confirms Dual Role in Touch Pleasantness but Not Touch-Pain Modulation
Year: 2026
Type: preprint
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. Key Points Unmyelinated C-tactile afferents are thought to relay the pleasantness of touch, however growing evidence suggests myelinated A-afferents may also play a role. Preferential nerve block of either A- or C-fibers reduced the perceived pleasantness of gentle brushing and deep pressure. A-fiber nerve block did not alter touch-induced modulation of heat pain. These findings suggest both A- and C-fibers are involved in touch pleasantness, but point to a pain-inhibiting role of C-tactile afferents.
Language: English
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7222223390