When older people can’t hear a word during a noisy holiday gathering, there may be too many brain cells active at once.

Seeking answers about how the brain works in the context of age-related hearing loss, Johns Hopkins University School of Medicine researchers say they have found that aged mice have the ability to “turned off” certain active brain cells in the midst of background noise worse than in young mice. The result, they say, is creating a “fuzzy” audio phase that makes it harder for the brain to focus on one type of sound—such as speech—and filter out ambient “noise”.

Scientists have long made the inevitable connection age-related hearing loss arrive hair cells in the inner ear is damaged or destroyed over time.

But the Johns Hopkins researchers say their new studies, described on December 7, Journal of neuroscienceshowed that the brain has a lot to do with the condition, and that such a hearing loss could be treated by retraining the brain to suppress intensely active neurons.

“There is more to hearing than listening,” says Patrick Kanold, PhD, professor of biomedical engineering at Johns Hopkins University and School of Medicine. Kanold notes that most people will experience hearing loss after age 65, such as being unable to hear individual conversations in a bar or restaurant.

Kanold and his team recorded the activity of 8,078 brain cellor neurons, in the auditory cortex of 12 aged mice (16-24 months) and 10 young mice (2-6 months).

First, the researchers gave the mice a chance to lick the faucet when they heard a sound. Then the same exercise is done during play”White noise” in the background.

do not have ambient noiseOld mice licked the faucet as well as young mice when they heard the sound.

When the researchers introduced white noise, in general, the older mice detected the sound and licked the faucet worse than the younger mice.

In addition, young rats tended to lick their trunks at the beginning or end of the tune. Older rats licked it at the start of the alarm signal but also licked before the tone appeared, suggesting that they thought the tone was present when it was not.

Next, to see how auditory neurons performed directly in such hearing tests, the researchers used a technique called two-photon imaging to look at the auditory cortex in mice. This technique uses fluorescence to identify and measure the activity of hundreds of neurons at once.

Under normal conditions, when the brain circuitry works correctly in the presence of background noise, some neuronal activity increases when the mouse hears that sound, and at the same time, other neurons are inhibited or Turn off. In most aged mice, however, the balance in favor of having most of the neurons active, and the neurons that were supposed to turn off when sound was played in a noisy setting, did not. so.

Additionally, the researchers found that just before the sound signal was emitted, neuronal activity was twice as high in older mice as in young mice, especially in males, causing the animals to lick the faucet before the alarm starts.

One possible reason for the result, Kanold said, is that “in older mice, the brain may be ‘fired’ or acting as if a ton present, when it’s not.”

Experiments with ambient noise also revealed that young mice experienced a change in the ratio between active and inactive neurons, while older mice had neurons more stable performance overall. Thus, young mice can cancel out the effects of ambient noise on neural activity while older mice could not, the researchers said.

“In older animals, background noise seems to make neuronal activity more ‘faint’, disrupting the ability to distinguish individual sounds,” Kanold said.

On the other hand, Kanold believes that due to the flexible learning potential of the mammalian brain, it can be “taught” to address dimming in older animals, including humans.

“There could be many ways to train the brain to focus on individual sounds amid a series of noises,” he said.

Kanold notes that more research is needed to accurately map the link between the inability to turn off certain neurons and hearing loss between ambient sounds, including the brain circuits involved, and how they are affected. changes with age, as well as potential differences between male and female animals.

Other contributors to the study were Kelson Shilling-Scrivo and Jonah Mittelstadt from the University of Maryland.