Tactile cues significantly modulate the perception of sweat-induced skin wetness independently of the level of physical skin wetness

Abstract

Filingeri D, Fournet D, Hodder S, Havenith G. Tactile cues significantly modulate the perception of sweat-induced skin wetness independently of the level of physical skin wetness. J Neurophysiol 113: 3462-3473, 2015. First published April 15, 2015 doi:10.1152/jn.00141.2015.-Humans sense the wetness of a wet surface through the somatosensory integration of thermal and tactile inputs generated by the interaction between skin and moisture. However, little is known on how wetness is sensed when moisture is produced via sweating. We tested the hypothesis that, in the absence of skin cooling, intermittent tactile cues, as coded by low-threshold skin mechanoreceptors, modulate the perception of sweat-induced skin wetness, independently of the level of physical wetness. Ten males (22 yr old) performed an incremental exercise protocol during two trials designed to induce the same physical skin wetness but to induce lower (TIGHT-FIT) and higher (LOOSE-FIT) wetness perception. In the TIGHT-FIT, a tight-fitting clothing ensemble limited intermittent skin-sweat-clothing tactile interactions. In the LOOSE-FIT, a loose-fitting ensemble allowed free skin-sweat-clothing interactions. Heart rate, core and skin temperature, galvanic skin conductance (GSC), and physical (w body ) and perceived skin wetness were recorded. Exercise-induced sweat production and physical wetness increased significantly [GSC: 3.1 S, SD 0.3 to 18.8 S, SD 1.3, P Ͻ 0.01; w body : 0.26 no-dimension units (nd), SD 0.02, to 0.92 nd, SD 0.01, P Ͻ 0.01], with no differences between TIGHT-FIT and LOOSE-FIT (P Ͼ 0.05). However, the limited intermittent tactile inputs generated by the TIGHT-FIT ensemble reduced significantly whole-body and regional wetness perception (P Ͻ 0.01). This reduction was more pronounced when between 40 and 80% of the body was covered in sweat. We conclude that the central integration of intermittent mechanical interactions between skin, sweat, and clothing, as coded by low-threshold skin mechanoreceptors, significantly contributes to the ability to sense sweat-induced skin wetness.

Neurophysiology of Skin Thermal Sensations

“…warm sensations). This has been recently demonstrated in one of this author' study (100), in which the alteration of the interactions skin-sweat-clothing under conditions of sweat-induced skin wetness, significantly modulated the perception of skin wetness, independently of the level of physical skin wetness. Finally, in light of this neural model, perceptual illusions such as the one where skin wetness is experienced as a result of cold-dry stimulation (102,103), could be explained and interpreted as the result of a sensory system which relies on rational integration mechanisms which are based on specific sensory inputs (e.g.…”

“…Alternatively exploring the two main sides of the perception of skin wetness [1) perception resulting from skin's contact with wet stimuli) (1, 15, 16, 71, 98-104, 109, 120, 191, 196, 227, 284, 285) 2) perception resulting from the active production of sweat (100,109,120,191)], these studies have contributed to increase our understanding of the psychophysical bases of human skin wetness perception.…”

“…This is particularly true under conditions of sweat-induced skin wetness (16,98,103). For example, under conditions of sweat-induced skin wetness, and especially when wearing clothing, skin wetness perception has been shown to be driven primarily by tactile stimuli in the form of intermittent mechanical interaction between skin, sweat and clothing (100,109,120,191). Interestingly, these findings are in line with what observed with for the mechanisms involved in the ability to sense skin wetness when in contact with external stimuli, and have therefore led to the current view for which the integration of specific thermal and tactile sensory cues is considered critical in order to experience the perception of skin wetness, irrespectively of the modality by which wetness is experienced (i.e.…”

“…thermal and tactile) underlie the ability to perceive skin wetness, has also to led to the investigation of the potential regional variability in skin wetness sensitivity across the body, and of its relationship with what known with regards to the regional differences in sensitivity observed in other somatosensory modalities (e.g. thermal sensitivity) (1,99,100,109,120,191). As a result, we now know that, during the contact with external stimuli, as well as a result of sweating, skin wetness can be perceived to a larger extent on certain regions of hairy skin (e.g.…”

Thermosensory mapping of skin wetness sensitivity across the body of young males and females at rest and following maximal incremental running

“…hygrosensation) contributes to the awareness of our own thermal state (Filingeri et al . ) and of that of our surrounding environments (Filingeri, ). For example, the experience of exercise‐ and sweat‐induced skin wetness is a well‐known trigger of thermal discomfort (Gagge et al .…”