When our skin is in contact with a wet surface, when we
touch a liquid, or when we sweat, we feel wet. This is one of the most common sensory
perception we experience in everyday’s life.
However, although it might be somewhat surprising, as
human beings we seem not to be provided with humidity receptors on the skin. Although
humidity-receptors have been previously described in some insects, none of
these receptors has ever been identified in human skin.
So, the question is: how do we feel the wetness if we
do not have physical entities on the skin which respond to variation in
humidity?
Our skin is provided with receptors responding to temperature,
pressure, vibratory and painful stimuli. However, no humidity receptors. Thus,
it has been suggested that the perception of skin wetness could be a complex
somatosensory experience resulting from the intra-sensory integration of
temperature and mechanical inputs on the skin. For example, we seem to interpret
the coldness experienced during the evaporation of water from the skin as a
signal of the presence of water, and thus wetness, on the skin’ surface. Also,
the mechanical and pressure related sensations experienced when e.g. sweat
moves on the skin, are interpreted as the occurrence of skin wetness. However,
although thermal and mechanical inputs seem to be acknowledged as the principal
inducers of the perception of local skin wetness, to date it is unclear how and
to what extent these sensory inputs interact in characterising this complex
perception.
The physical processes which occur when the skin is in contact with moisture (i.e. heat transfer and mechanical interactions between the skin and the environment) generate thermal and mechanical inputs which could be integrated and combined at different anatomical levels through specific multisensory pathways. Hence, it is not the contact of the skin with moisture per se, but rather the integration of particular sensory inputs which seems driving the perception of local skin wetness during the contact with a wet surface. It could therefore be suggested that the perception of local skin wetness is a “perceptual illusion” shaped by sensory experience.
The physical processes which occur when the skin is in contact with moisture (i.e. heat transfer and mechanical interactions between the skin and the environment) generate thermal and mechanical inputs which could be integrated and combined at different anatomical levels through specific multisensory pathways. Hence, it is not the contact of the skin with moisture per se, but rather the integration of particular sensory inputs which seems driving the perception of local skin wetness during the contact with a wet surface. It could therefore be suggested that the perception of local skin wetness is a “perceptual illusion” shaped by sensory experience.
This has been demonstrated by our recent findings in
which the synthetic nature of the perception of skin wetness has been unmasked.
We have indeed 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 0.14 to 0.41°C/s. When blindfolded individuals were exposed to
cold-dry stimuli, reproducing the same cold sensations experienced when the
skin is physically wet, these individuals perceived skin wetness, even though
they did not touch anything which was wet.
These findings are reported in the following paper,
which today, I would like to bring to you attention:
D. Filingeri, et al., The role of decreasing contact
temperatures and skin cooling in the perception of skin wetness, Neurosci.
Lett. (2013)
Increasing
the knowledge about the neurophysiological bases of the perception of wetness
can be useful both for clinical and industrial applications. On the clinical
side, it might beused for diagnostic purposes in patients with sensory
disorders e.g. diabetic neuropathy. On the industrial side, it might sup-port
the development of new strategies in clothing design, as this perception has
been shown to play a significant role in the onset of thermal discomfort.
Enjoy!
Davide
Filingeri
PhD
Researcher
Environmental
Ergonomics Research Centre
Loughborough
University, UK
Neurosci Lett. 2013 Jul 22. pii: S0304-3940(13)00647-2. doi: 10.1016/j.neulet.2013.07.015. [Epub ahead of print]
The role of decreasing contact temperatures and skin cooling in the perception of skin wetness.
Source
Environmental Ergonomics Research Centre, Loughborough Design School, Loughborough University, Loughborough LE11 3TU, UK. Electronic address: D.Filingeri@lboro.ac.uk.
Abstract
Cold sensations are suggested as the primary inducer of the perception of skin wetness. However, limited data are available on the effects of skin cooling. Hence, we investigated the role of peripheral cold afferents in the perception of wetness. Six cold-dry stimuli (producing skin cooling rates in a range of 0.02-0.41°C/s) were applied on the forearm of 9 female participants. Skin temperature and conductance, thermal and wetness perception were recorded. Five out of 9 participants perceived wetness as a result of cold-dry stimuli with cooling rates in a range of 0.14-0.41°C/s, while 4 did not perceive skin wetness at all. Although skin cooling and cold sensations play a role in evoking the perception of wetness, these are not always of a primary importance and other sensory modalities (i.e. touch and vision), as well as the inter-individual variability in thermal sensitivity, might be equally determinant in characterising this perception.
Copyright © 2013. Published by Elsevier Ireland Ltd.
KEYWORDS:
Psychophysics, Skin wetness, Temperature, Thermoreceptors, Touch
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