Unmyelinated Afferents Constitute a Second System Coding Tactile Stimuli of the Human Hairy Skin

1999/06/01 by Å. B. Vallbo, H. Olausson, Håkan Olausson +2 · 574 citations
Engineering · Medicine · Neuroscience · Psychology · #Advanced Sensor and Energy Harvesting Materials #Afferent #Anatomy #Cognitive psychology #Communication #Forearm #Medicine #Microneurography #Neural dynamics and brain function #Neuroscience #Psychology #Sensory system #Stimulus (psychology) #Subliminal stimuli #Tactile and Sensory Interactions

paper · pdf · doi:10.1152/jn.1999.81.6.2753

published in Journal of Neurophysiology 81(6), 2753-2763 (American Physiological Society)

openalex publication_date 1999/06/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

Impulses were recorded from unmyelinated afferents innervating the forearm skin of human subjects using the technique of microneurography. Units responding to innocuous skin deformation were selected. The sample (n = 38) was split into low-threshold units (n = 27) and high-threshold units (n = 11) on the basis of three distinctive features, i.e., thresholds to skin deformation, size of response to innocuous skin deformation, and differential response to sharp and blunt stimuli. The low-threshold units provisionally were denoted tactile afferents on the basis of their response properties, which strongly suggest that they are coding some feature of tactile stimuli. They exhibited, in many respects, similar functional properties as described for low-threshold C-mechanoreceptive units in other mammals. However, a delayed acceleration, not previously demonstrated, was observed in response to long-lasting innocuous indentations. It was concluded that human hairy skin is innervated by a system of highly sensitive mechanoreceptive units with unmyelinated afferents akin to the system previously described in other mammals. The confirmation that the system is present in the forearm skin and not only in the face area where it first was identified suggests a largely general distribution although there are indications that the tactile C afferents may be lacking in the very distal parts of the limbs. The functional role of the system remains to be assessed although physiological properties of the sense organs invite to speculations that the slow tactile system might have closer relations to limbic functions than to cognitive and motor functions.

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