In a previous post on this blog, I introduced the topic of "how humans perceive cutaneous wetness" (see Why wet is wet? A study on the sensory integration underpinning the perception of skin wetness). The topic is of interest for me as it represents the main research question of my PhD.
Based on the outcomes of a recent paper we published on the topic (Filingeri D,
Redortier B, Hodder S, Havenith G. (2013) The role of decreasing contact
temperatures and skin cooling in the perception of skin wetness Neuroscience
Letters, 551:65-69), in the mentioned post I discuss possible neurophysiological and cognitive mechanisms which might underpin humans' ability to sense cutaneous wetness and humidity. Although it might be somewhat surprising, as human beings we are indeed not provided with humidity receptors on the skin.
In support of the hypothesis that we “learn” to perceive the wetness experienced when our skin is in contact with a wet surface, when a liquid is touched, or when sweat is produced through a complex multisensory integration, we have recently published another study, in which we investigate the role of temperature and mechanical inputs, and their interaction, in the ability to sense cutaneous wetness:
Neuroscience. 2013 Nov 20. pii: S0306-4522(13)00959-7. doi: 10.1016/j.neuroscience.2013.11.019. [Epub ahead of print]
Thermal and tactile interactions in the perception of local skin wetness at rest and during exercise in thermo-neutral and warm environments.
Source
Environmental Ergonomics Research Centre, Loughborough Design School, Loughborough University, Loughborough, LE11 3TU, UK. Electronic address: D.Filingeri@lboro.ac.uk.
Abstract
The central integration of thermal (i.e. cold) and mechanical (i.e. pressure) sensory afferents is suggested as to underpin the perception of skin wetness. However, the role of temperature and mechanical inputs, and their interaction, is still unclear. Also, it is unknown whether this intra-sensory interaction changes according to the activity performed or the environmental conditions. Hence, we investigated the role of peripheral cold afferents, and their interaction with tactile afferents, in the perception of local skin wetness during rest and exercise in thermo-neutral and warm environments. Six cold-dry stimuli, characterised by decreasing temperatures [i.e. -4, -8 and -15°C below the local skin temperature (Tsk)] and by different mechanical pressures [i.e. low pressure (LP): 7 kPa; high pressure (HP): 10 kPa], were applied on the back of 8 female participants (age 21 ± 1 years), while they were resting or cycling in 22 or 33°C ambient temperature. Mean and local Tsk, thermal and wetness perceptions were recorded during the tests. Cold-dry stimuli produced drops in Tsk with cooling rates in a range of 0.06 to 0.4°C/s. Colder stimuli resulted in increasing coldness and in stimuli being significantly more often perceived as wet, particularly when producing skin cooling rates of 0.18°C/s and 0.35°C/s. However, when stimuli were applied with HP, local wetness perceptions were significantly attenuated. Wetter perceptions were recorded during exercise in the warm environment. We conclude that thermal inputs from peripheral cutaneous afferents are critical in characterizing the perception of local skin wetness. However, the role of these inputs might be modulated by an intra-sensory interaction with the tactile afferents. These findings indicate that human sensory integration is remarkably multimodal.
Copyright © 2013. Published by Elsevier Ltd.
KEYWORDS:
HP, High pressure, LP, Low pressure, Mechano-receptors, Perception, Sensory integration, Skin temperature, Skin wetness, T(sk), Thermo-receptors, Variation in local skin temperature, ΔT(sk)
The novelty of our findings is represented by the discovery of an unexpected intra-sensory interaction between thermal and tactile sensory afferents which affected the way wetness was sensed. In this new study we have indeed observed that thermal afferents are critical in characterizing the perception of skin wetness. In line with our previous finding, we have shown that an illusion of local skin wetness can be evoked during the skin’s contact with a cold-dry surface producing a range of skin cooling rates of 0.06 to 0.4°C/s. However, we have also observed that tactile afferents can modulate the perception of skin wetness. Indeed, when a higher mechanical pressure was applied on the skin, the same stimuli were perceived as less cold and less wet.
This study provides new evidence in support of the hypothesis of a tactile-mediated attenuation of the perception of local skin wetness. Also, they indicate that cold sensation and wetness perception might not depend solely on the parameters of the thermal stimulus.
If you are interested in read more about this, have a look at the full paper available here:
Enjoy!
Davide Filingeri
PhD Researcher
Environmental Ergonomics Research Centre
Loughborough University, UK
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