ELife external hair cells regulate the sensitivity of the ear to sound

October 28, 2019 / BIOON / -- a new study published in the Journal of eLife recently shows that the tiny hair cells outside the ear can regulate the sensitivity of adjacent inner hair cells to sound, rather than play an amplifier role These findings in gerbils help us understand the role of outer hair cells in hearing These findings also contribute to the development of better ways to protect these vulnerable cells from harm and prevent hearing loss Photo source: tiny hair like cells in the inner ear of https://cn.bing.com act like microphones, converting sound induced vibrations into electrical signals interpreted by the brain These inner hair cells work with outer hair cells, and the role of outer hair cells in hearing is sometimes controversial Anna vavakou, a doctoral student in the Department of Neuroscience at Erasmus University Medical Center in Rotterdam, the Netherlands, explained: "when the outer hair cells are damaged, the vibration is much smaller than that of a healthy ear This leads scientists to believe that outer hair cells actively amplify sound, but there is a problem with this theory The electrical properties of outer hair cells make them slow to respond to the rapid vibration of high frequency sound, especially for animals with ultrasonic hearing "To better understand the function of outer hair cells, vavakou and her colleagues used a new technique called optical coherence tomography vibration to measure the tiny actions of living gerbil outer hair cells in response to sound These cells can move quickly and respond to sounds up to 2.5 kHz, or about half the octave on a piano keyboard At a higher pitch, the team found that the cells were less able to keep up with the vibrations This shows that although gerbils have good ultrasonic hearing, their outer hair cells can not amplify these sounds, but they can accurately track the sound changes "Instead of amplifying the sound, these cells monitor the sound level and adjust the sensitivity accordingly," vavakou said This is what engineers call automatic gain control, which is used in many devices, such as mobile phones "A better understanding of the function of these outer hair cells is essential," explains senior author Marcel van der Heijden, head of the auditory peripheral laboratory at the University of Erasmus medical center "Specific drugs such as noise and antibiotics can easily damage these cells, leading to hearing loss To find out the exact function of them is helpful to guide the prevention and even cure of common forms of hearing loss "Reference: Anna vavavakou et al, the frequency limit of outer hair cell mobility measured in vivo, eLife (2019) Doi: 10.7554/elife.47667