2023-07-05 16:00:00
Hearing is precious: it can disappear or deteriorate for many reasons. One of them is exposure to loud noises repeatedly. If for a long time, scientists have understood that this might lead to hearing loss, they were unable to decipher the phenomenon. A team from Linköping University in Sweden has just discovered a key element to understanding it. Their results are published in Cellular and Molecular Life Sciences.
Hearing loss: a mysterious hearing signal for 70 years
“When the ear is exposed to loud sounds, such as at a concert or in a noisy environment, hearing can be temporarily impaired,” they recall in the preamble. If exposure to these noises is repeated, hearing damage may be irreversible. To understand the origin of these losses, the researchers looked at the inner ear. It contains regarding 15,000 sensory cells, called hair cells. “When hit by sound waves, hair cells transform the vibrations into electrical nerve signals, they develop. These signals are directed to the brain, which interprets them, and only then can we hear the sound.” These signals are divided into two types: AC and DC. The former are well known to scientists: they give the brain information on the intensity and frequency of sound. “But the DC signal has remained a mystery, explain the authors. Since its discovery regarding 70 years ago, scientists have wondered what its function might be.”
A signal to warn of a danger to hearing
In fact, the two signals are linked: the DC signal causes a slight offset of the AC signal in a positive or negative direction. “Various studies trying to characterize the DC signal have come to different conclusions,” say the Swedish researchers. This time, they demonstrated that this DC signal polarity changes from positive to negative when the cochlea, another name for the inner ear, has been exposed to harmful noise. “In other words, the signal can provide an indication of the state of health of the ear”, they analyze. The authors believe it might be a way for the body to inform the brain of the condition of the ear. “The brain can amplify a weak signal from the cochlea, notes Pierre Hakizimana, a research engineer at Linköping University. If informed that the ear is not functioning normally, the brain does not have to spend resources trying improve the signal to decode the sound of an injured ear.”
Hearing loss: future screening methods?
According to him, this signal is promising for the detection of hearing disorders. Further research might lead to the development of new diagnostic techniques for hearing loss related to harmful noise. According to theHealth Insurance10% of the French population suffers from hearing loss.
1688573403
#signal #ear #brain #involved
