February 1, 2023

Taylor Daily Press

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Grandpa couldn’t understand you at Christmas dinner? New research suggests it may not just be his ears

Part of the problem lies in the brain. This is the good news too. Because this means the brain can be trained to filter out background noise.

The older the elderly, the worse their hearing gets. Unfortunately, it is the inevitable truth. Scientists know that “age-related hearing loss” may be related to the damage of hair cells in the inner ear over time. But researchers are now in New study Discover that there is much more to it than that. The brain seems to have a lot to do with this condition.

Conversation in a noisy restaurant
Most people experience some form of hearing loss after they reach the age of 65. For example, it becomes difficult to capture individual conversations taking place at your own table in the middle of a crowded and noisy restaurant. And the ears can’t just be blamed. “Hearing involves more than just the ears,” says researcher Patrick Kanold.

To elucidate the brain’s role in age-related hearing loss, the researchers conducted experiments on mice. Kannold and his colleagues recorded the activity of up to 8,078 brain cells (or neurons), in the so-called auditory cortex (the part of the brain where sound stimuli are processed) of 12 old (16-24-month-old) and 10 young (2- 6 months).

Experiment – did experiments
Even before the experiments began, the rats were predisposed to licking a water tap when they heard a certain tone. Then the same exercise was performed while the researchers were playing “white noise” in the background.

What is white noise?
White noise is monotonous background noise, in which the average amplitude is the same for each frequency. There are examples from nature, such as sea waves, rain, or wind blowing through trees, but many devices also produce white noise, such as a fan, a vacuum cleaner, or a car engine. It is now used to soothe crying babies, to help you sleep better or to focus better.

Without the ambient noise, the old mice, when they heard a tone, would lick the water spout just like the young mice. But when the researchers added white noise, the old mice licked the faucet much less, indicating that they heard the tone worse. In addition, they sometimes licked the water spigot even before playing the tune. This indicates that the ancient rats thought they heard a tone, when in fact it wasn’t.

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auditory cortex
Next, to see how auditory neurons behaved during a hearing test, the researchers used a sophisticated imaging technique that allowed them to view the auditory cortex of mice. This leads to an amazing discovery. Under normal circumstances, when brain circuits function properly in the presence of ambient noise, the moment a rat hears the tone, some neurons become more active. At the same time, other neurons were suppressed or turned off. However, in most older mice, the balance has tipped. They mostly had active nerve cells. This is because neurons that were supposed to be suppressed or turned off remained active. In short, the brains of old mice failed to suppress some neurons when the tone was played in the presence of loud background noise.

This means that the young mice are in fact experiencing constant shifts in the ratio of active to inactive neurons. On the other hand, older mice generally have a more consistent number of active neurons. Transitions allow young mice to suppress ambient noise, while older mice fail to do so. According to the researchers, this means that the brain has more difficulty focusing on one type of sound – such as spoken words – and filtering out the surrounding “noise”. “The ability to distinguish individual sounds is poor,” Kanold says.

So when Grandpa couldn’t get you right during Christmas dinner, it wasn’t just his ears. His brain also plays a role in this. And that, too, according to the researchers, is the good news. The human brain is plastic, which means that we can influence the functioning of the brain and the connections in the brain. So Kanold believes that because of this flexibility, the brain can be trained to filter out background noise. “There may be ways to train the brain to focus on a specific sound amid a cacophony of noise,” he believes.

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Further research is already underway. For example, according to Kanold, more research is needed to determine the exact relationship between the inability to turn off certain neurons in the midst of ambient noise and the eardrum. Kanold also wants to further study the brain circuits involved and how they change with age, as well as potential differences between men and women.