Stimulus-response relationships in the cutaneous slowly-adapting mechanoreceptor in hairy skin of the cat.

Abstract The skin mechanoreceptor responded to sustained mechanical stimulation with a three-phase action potential sequence composed of displacement-rate, transient, and displacement sensitive components. The stimulus-response relations of the displacement-rate phase were studied by application to the skin pads containing the receptor terminal of linear displacements over a stimulus continuum ranging from 0.26 to 40.8 μ/msec with final displacement of 250 μ. In response, the full carrying capacity of the group-A fiber was utilized; pulse trains of uniform interval, averaging 90 to 100 impulse/sec, were evoked. Over much of the stimulus range, the response frequency was related to the displacement rate by a power function. The alpha and beta coefficients of this relationship ranged from 1.919 to 2.396 and 0.304 to 0.592, respectively, for the twenty-nine terminals studied at normal skin temperature. Greater uniformity was obtained among receptors within a tactile unit than with those among units. The data from all the terminals were found to be ordered by the highly significant negative correlation among the coefficients, a relationship which provided a description of the stimulus-response boundaries of the system. Skin temperature (17–40 C) influenced the sensitivity, general activity level, and extent of the operating region. These effects appeared to be related to axonal properties which are influenced by temperature. Displacement-rate sensitivity was shown to be a dominant property of this receptor.