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Hearing impaired people have a finer sense of touch
In a study recently published in the journal "Nature Neuroscience", a research team led by study leader Thomas Jentsch found that genetically determined hearing loss also affects the sense of touch. This is due to a gene that has so far only been identified in connection with hearing loss. It has now been discovered that this gene also affects the previously little explored sense of touch. According to the study paper, the sense of touch of people with genetically determined hearing loss is more sensitive than that of people with hearing loss.
Genetic hearing loss
The study examined Spanish and Dutch families with DFNA2 genetic hearing loss. With this form of hearing loss, the function of some hair cells in the ear is disturbed by mutation.
To hear, the fine hairs in the ear vibrate in the rhythm of the sound waves. This causes potassium ions to flow into the hair cells and a nerve signal is transmitted to the brain. The potassium ions then flow off again via a channel in the cell membrane. In the hearing impaired, this channel is defective due to a mutation. The channel consists of a protein molecule called KCNQ4. Overload causes the sensory cells to die.
Now researchers have found that this mutation also affects the sense of touch. Study leader Thomas Jentsch from the Leibniz Institute for Molecular Pharmacology (FMP) reports: "But we found that KCNQ4 is not only found in the ear, but also in certain sensory cells of the skin." Jentsch continued: "This gave us the idea that the mutation could also affect the sense of touch. In fact, we were able to show this in close cooperation with the laboratory of Gary Lewin, a colleague from the MDC who specializes in tactile sensation.
How does the sense of touch work?
Without being aware of it, the sense of touch gives us vital information about our environment at every moment. If we reach for something, we immediately know from the touch whether it is hot, cold, smooth or rough. Our surface perception works via receptors in the skin, which are divided into pain, mechano and thermoreceptors. So we can perceive pain, vibrations, touch, temperature and pressure. Since the sense of touch is still largely unexplored, it is only possible to speculate about the exact mechanisms. However, it is known that sensory cells are present in the skin for the various touch stimuli. The deformation of these cells creates an electrical nerve signal that is passed on to the brain.
In order to track down the connection between genetically determined hearing loss and the changed sense of touch, the researchers first developed an investigation model using mice that showed the same mutation of the potassium channel as people with this form of hearing loss. The touch receptors in the skin do not die due to the defective channel as in the ear. However, the mutant mice showed that they responded to mechanical stimuli with a different electrical signal. The touch receptors were much more sensitive to vibrations in the low frequency range. The researchers concluded that the potassium channel appears to act as a kind of damper. If the channel is normal, only fast vibrations and higher frequencies are perceived. If the canal is damaged, the skin becomes more sensitive.
When examining the families, the researchers came to the same conclusion. The children who had mutations in the potassium channel could feel vibrations much slower than their healthy siblings. Gary Lewin and Thomas Jentsch summarize: “The skin has several different types of mechanoreceptors that respond to different stimulus qualities, especially to different frequency ranges. The interaction of different receptor classes is important for the sense of touch. Although the receptors we investigated become more sensitive as a result of loss of the potassium channel, the disadvantage of the wrong ‘mood’ on other frequencies may outweigh them. With KCNQ4 we have for the first time identified a human gene that changes the properties of the sense of touch. ”(Source: (Nature Neuroscience, 2011; DOI: 10.1038 / nn.2985)