Neuromechanical representation of fabric-evoked prickliness: a fiber-skin-neuron model

Abstract

Cutaneous Ad nociceptors encode the material and geometrical features of fiber ends evoking prickliness sensation by generating neural spikes in response to indentation of human skin, however, understanding of the underlying neuromechanism of fabric-evoked prickliness is still far from clear. This work develops and validates a fiberskin-neuron (mechanosensitive Ad-nociceptors) model that combines an analytical model of fiber-skin indentation, a sigmoidal function of neuronal transduction, and a leaky integrate-and-fire model of neuronal dynamics. Firstly, the model is validated to be capable of capturing the typical neurphysiological features of cutaneous Ad nociceptors and the psychophysical phenomenon. And then, several case studies with respect to statistical features of fiber ends are carried out, and the resulting neural responses are calculated to explore the relationship between statistical features in study and evoked responses. The analysis of predicted action potentials over one second indicates that they systematically change with statistical features of fiber ends protruding above fabric surfaces, and the fitted stimulusresponse relationship of Ad nociceptors is highly similar to the stimulus-sensation relationship of prickliness rating magnitude. It follows that there might exist a linear relationship between fabric-evoked neurophysiological responses and psychophysical responses. These results provide significant new insight into the fabric-evoked prickliness sensation and raise interesting questions for further investigation, and the model described here bridges the gap between those models that transform fiber ends properties to firing rates.

A modular modeling approach for investigating wool critical buckling from biologically variable along-fiber microstructure

“…For a perfectly cylindrical fiber, the flexural rigidity would increase with the square of CSA (fourth power of radius), all other factors being constant. However, from our working shown previously (and in particular see Equation (12)), the second moment of area (and thus flexural rigidity) will decrease inversely with the ratio of ellipticity expressed as the ratio of the major to minor axes. In addition, variation in composition along the fiber will contribute to changes in flexural rigidity.…”

“…These are associated with two independent neural coding mechanisms, namely Ad nociceptors and C-fiber nociceptors, respectively. 11,12 A fiber that generates this form of discomfort causes a local indentation in the skin, with the resulting stress being propagated through underlying tissues to the transduction sites of nerve receptors. 12 In addition, the fiber must be stiff enough to resist buckling at the threshold force for nerve activation; in the average human, it may be as low as 75 mg force, or 0.74 mN.…”

“…11,12 A fiber that generates this form of discomfort causes a local indentation in the skin, with the resulting stress being propagated through underlying tissues to the transduction sites of nerve receptors. 12 In addition, the fiber must be stiff enough to resist buckling at the threshold force for nerve activation; in the average human, it may be as low as 75 mg force, or 0.74 mN. 11 Garnsworthy et al 11 suggested that the minimum length required for a fiber to cause prickle is about 200 mm because otherwise the indentation of the skin would lead to increased contact area of fabric and skin, reducing the pressure at the fiber end.…”

Non-pharmacological interventions in the management of atopic dermatitis

“…e spiky nature of wool fibers and the innumerable tiny harpoons at its fiber endings evoke prickly sensation in skin. [30,31] Cotton or silk fabrics are better tolerated by atopic individuals. However, as silk is expensive, for all practical purposes, loose fitting, light colored, open weaved cotton fabrics are considered near to ideal and more acceptable by atopic individuals.…”