It's a problem that becomes more common as we age: a friend is talking to you, you see his mouth moving, you hear his voice, but you just can't hear the word over the cacophony of other voices and music.
is part of the problem, new research finds, and may lie not in the ear itself, but in the brain's ability to filter out background noise and focus on a sound.
"Our ability to hear in noisy environments depends on how well our brain rhythms are synchronized with the rhythms of the sounds we're trying to hear," says Molly Henry, lead author of the study published today (June 27) in the journal Nature Communications. Lead author and a postdoctoral researcher in neuroscience at the University of Western Ontario, in the U.S.
, about one-third of people between the ages of 65 and 74 suffer from hearing loss, and nearly half of people over the age of 75 suffer from hearing loss, according to the U.S. National Institutes of Health.
Henley, who was educated at the Max Planck Institute in Germany, was born in the U.S. in 1971 and is a member of the National Academy of Sciences. （A study conducted while Henry was a postdoctoral fellow at the Max Planck Institute in Germany
, she and her colleagues analyzed what happens to the brains of older people when they can't hear in noisy environments. [10 Things You Didn't Know About the Brain]
The researchers used a technique known as electroencephalography, which involves having participants wear a cap with many electrodes. In this study, the researchers tested the brains of 20 young people between the ages of 18 and 31 and 20 older people between the ages of 60 and 70 by listening to them.
Each was essentially placed in a loud party scene. A constant background noise - in this case, a sound similar to a U.S. police siren - made a piercing sound when participants were asked to try to detect a target signal. As they did so, electrode caps on their heads measured the electrical activity generated by the coordinated firing of neurons in the brain.
Hearing sounds required participants to both suppress irrelevant noises and enhance important sounds, the study found,
When you listen to "sounds, the electronic firings in your brain are synchronized with the rhythms of the sounds, so they have the same temporal structure," Henry told Live Science, which allows you to predict upcoming information. information that's coming.
The researchers found that young people were able to target signals while filtering out extraneous noise.
Brain signals in older people, on the other hand, suggest they have trouble filtering out background noise. Neural signals in the brains of older people fire out in a pattern synchronized with irrelevant sirens, which inhibits their ability to detect target signals. [27 Strangest Medical Cases]
"For older people, it's all mixed together, creating an overall noise," Henry says.
One aspect of this type of filtering is less clear, and Henry offers two possible explanations. It could be that a deterioration in the ear's ability to hear actually leads to a decrease in the brain's ability to filter noise and hear a single sound. Or, it could be that the brain's ability to hear has eroded, independent of any changes in the ear. Henry said that the older people in the study did not have hearing loss and had "very good" hearing, but they still did not hear as well as younger people.
"Can hearing loss cause brain changes?" ? Or do the brain changes happen on their own?" Henry says this is something we don't know yet.
It's a key question as the U.S. population ages and more people face age-related hearing loss. The number of Americans 65 and older is expected to more than double, from 46 million today to more than 98 million by 2060, according to the Population Reference Bureau.
Hearing aids may help some people, but the devices don't always help those whose hearing loss is primarily brain-related, Henry added.
"The truth is that hearing aids often "don't work very well," she said, adding that we need to understand what's going on in the brain.
Originally published in the journal Life Sciences.