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Wetness Sense of Touch

Humans Can Only Sense Temperature and Pressure. We Can Not Sense Wetness.

Humans have five major senses: sight, taste, sound, touch, and smell. In addition to this, with the sense of touch, we can feel temperature and pressure. But did you know humans cannot sense wetness?

A study was conducted by researchers from Loughborough University and Oxylane Research. The answer is a resounding no. We can sense temperature and pressure but not wetness.

How Do Humans Sense Wetness?

Wetness perception is linked to our capacity to feel low temperature and tactile sensations like pressure and texture, according to researchers from Loughborough University and Oxylane Research. They also looked at the role of A-nerve fibers, which convey temperature and tactile information from the skin to the brain, as well as the effect of diminished nerve activity on wetness perception. Finally, they speculated that because hairy skin is more sensitive to heat stimuli, it would be more sensitive to moisture than glabrous skin like palms of hands, soles of feet, which is more responsive to tactile stimuli.

Thirteen healthy male college students were subjected to warm, neutral, and cold, wet stimuli by Davide Filingeri et al. 

They examined the volunteers’ forearms and fingertips. The researchers also did the moist stimulus test with and without a nerve block. The nerve block was accomplished by inflating a compression cuff to a level that dampened A-nerve sensitivity.

Wet perception increased as temperature declined, indicating that participants were far more likely to detect cold, wet stimuli than warm or neutral wet stimuli. The researchers also discovered that when the A-nerve activity was stopped, the patients were less sensitive to dampness and that hairy skin is more sensitive to wetness than glabrous skin. These findings add to our knowledge of how people interpret wetness and offer a novel model for how the brain processes this experience.

Based on a concept of perceptual learning and Bayesian perceptual inference, we developed the first neurophysiological model of cutaneous wetness sensitivity centered on the multisensory integration of cold-sensitive and mechanosensitive skin afferents, Our results provide evidence for the existence of a specific information processing model that underpins the neural representation of a typical wet stimulus.

Loughborough University and Oxylane Research team

(Source; Neuroscience News)

A Neurophysiological Model of Human Cutaneous Wetness

Although the capacity to detect skin wetness and humidity is crucial for behavioral and autonomic adjustments, people lack particular wetness receptors on their skin. 

It has been claimed that we learn to detect wetness when the skin touches a wet surface or when sweat is created by a multimodal integration of thermal and tactile sensations generated by the skin-moisture interaction. However, the specific roles of temperature and tactile inputs and how our nervous system integrates them peripherally and centrally are still poorly understood. 

The idea that the central integration of coolness and mechanosensation, as served by peripheral A-nerve afferents, is the fundamental neuronal process underlying human moisture sensitivity was evaluated in this study.

The researchers discovered that, despite having the same moisture content, warm-wet and neutral-wet stimuli were judged as considerably less wet than cold-wet stimuli during a quantitative sensory test. Wetness perception was also dramatically reduced when a targeted reduction reduced cutaneous cold and tactile sensitivity in the activity of A-nerve afferents. 

The Team established the first neurophysiological model of cutaneous moisture sensitivity centered on the multisensory integration of cold-sensitive and mechanosensitive skin afferents, based on a concept of perceptual learning and Bayesian perceptual inference. 

The findings support the idea that a unique information processing model underpins the brain representation of a typical moist input. These findings help to explain how humans perceive skin wetness as warm, neutral, or chilly. (Source: Neuroscience News)

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