Afferent activity in thin myelinated and unmyelinated cutaneous nerve fibers during mechanical stimulation of skin receptors

Afferent activity in thin myelinated and unmyelinated cutaneous nerve fibers was analyzed by an impulse collision method and by methods improving the signal-to-noise ratio in the record of the antidromic action potential. The following groups were distinguished among the thin myelinated and unmyelinated nerve fibers on the basis of the results of investigation of conduction velocities, thresholds of electrical excitation, and response to mechanical stimulation: A ₁ (conduction velocity 30-14 m/sec) — a relatively larger number of these fibers conducts excitation in response to weak mechanical stimulation; A ₂ (14–4.0 m/sec) — the receptors of these fibers are more easily excited by a strong stimulus; a group of "mixed" fibers, containing myelinated and unmyelinated nerve fibers (4–2 m/sec), conducting excitation in response to both types of mechanical stimulation; C₁ (2.0–1.0 m/sec) — a fairly large number of these unmyelinated fibers conducts impulses in response to weak mechanical stimulation; C₂ (1.0–0.15 m/sec) the majority of fibers of this group is connected with receptors requiring strong mechanical stimulation for their excitation.Research Institute of Applied Mathematics and Cybernetics, N. I. Lobachevskii State University, Gor'kii. Translated from Neirofiziologiya, Vol. 8, No. 1, pp. 67–75, January–February, 1976.