People with a certain form of inherited（遗传的） hearing loss have increased sensitivity to low frequency vibration, according to a study by Professor Thomas Jentsch of the Leibniz-Institut für Molekulare Pharmakologie (FMP)/Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch and Professor Gary Lewin (MDC), conducted in cooperation with clinicians from Madrid, Spain and Nijmegen, the Netherlands. The research findings, which were published in Nature Neuroscience, reveal previously unknown relationships between hearing loss and touch sensitivity: In order to be able to 'feel', specialized cells in the skin must be tuned like instruments in an orchestra（管弦乐队） .

The members of the Spanish and Dutch families who participated in the study were quite amazed when the researchers from Berlin unpacked their testing equipment. Many of the family members suffer from hereditary DFNA2 hearing loss, but the researchers were less interested in their hearing ability than in their sense of touch. The hearing impairment（听觉障碍） is caused by a mutation which disrupts the function of many hair cells in the inner ear. This mutation, the researchers suspected, might also affect the sense of touch.

Tiny, delicate hairs in our inner ear vibrate to the pressure of the sound waves. The vibrations cause an influx of positively charged potassium（钾） ions into the hair cells. This electric current produces a nerve signal that is transmitted to the brain -- we hear. The potassium ions flow through a channel in the cell membrane and again out of the hair cells. This potassium channel, a protein molecule called KCNQ4, is destroyed by the mutation in hearing-impaired people. The sensory cells gradually die off due to overload. "But we have found that KCNQ4 is present not only in the ear, but also in some sensory cells of the skin," Thomas Jentsch explained. "This gave us the idea that the mutation might also affect the sense of touch. And this is exactly what we were able to show in our research, which we conducted in a close collaboration with the lab of Gary Lewin, a colleague from the MDC who is specialized in touch sensation."

Whether we caress our child, search in our bag for a certain object or hold a pen in our hand -- each touch conveys a variety of precise and important information about our environment. We distinguish between a rough and smooth surface by the vibrations that occur in the skin when the surface is stroked. For the different touch stimuli there are sensory cells in the skin with different structures -- through the deformation of the delicate structures, electric nerve signals are generated. Exactly how this happens is still a mystery -- of the five senses of Aristoteles, the sense of touch is the least understood.