Scientists at Johns Hopkins Medicine have found that old mice are less able than young mice to “switch off” particular actively firing brain cells in the presence of ambient noise. This leads to a “fuzzy” sound phase that makes it hard for the brain to concentrate on a particular noise and filter out surrounding sound. The scientists recommend that age-related hearing loss may be treated by retraining the brain to minimize the activity of these neurons.
Study of hearing in old and young mice suggests the brain may be trained to filter out background noise.
Trying to find responses about how the brain works amid age-related hearing loss, Johns Hopkins Medicine scientists found that old mice were less capable than young mice of “switching off” particular actively shooting brain cells in the midst of ambient sound. The outcome, they say, produces a “fuzzy” sound stage that makes it tough for the brain to concentrate on one type of sound– such as spoken words– and filter out surrounding “noise.”.
Scientists have actually long linked unavoidable age-related hearing loss to hair cells in the inner ear that become harmed or destroyed with time.
The Johns Hopkins researchers say their new research studies, described on December 7 in The Journal of Neuroscience, suggest that the brain has much to do with the condition, and it may be possible to treat such hearing loss by re-training the brain to tamp down the wildly shooting neurons.
When grandpa cant hear words at a noisy vacation gathering, too lots of brain cells may be firing at once, say researchers.
” Theres more to hearing than the ear,” says Patrick Kanold, Ph.D., teacher of biomedical engineering at The Johns Hopkins University and School of Medicine. Kanold notes that many people will experience some sort of hearing loss after age 65, like the inability to choose private discussions in a bar or restaurant.
Kanold and his team recorded the activity of 8,078 brain cells, or nerve cells, in the acoustic cortex brain area of 12 old mice (16– 24 months old) and 10 young mice (2– 6 months old).
First, the scientists conditioned the mice to lick a water spout when they heard a tone. The same exercise was carried out while playing “white noise” in the background.
Without the ambient noise, the old mice licked the water spout just as well as the young mice when they heard the tone.
When the researchers presented the white noise, in general, the old mice were worse at identifying the tone and licking the spout than the young mice.
The young mice tended to lick the spout at the start or the end of the tone. Older mice licked it at the start of the tone cue however also showed licking before the tone was provided, suggesting that they thought a tone was present when there wasnt one.
Next, to see how auditory nerve cells performed straight throughout such hearing tests, the scientists utilized a method called two-photon imaging to peer into the auditory cortex in the mice. The technique utilizes fluorescence to recognize and measure the activity of hundreds of neurons at the exact same time.
Under regular conditions, when brain circuitry worked properly in the presence of ambient sound, some nerve cell activity increased when the mice heard the tone and, at the same time, other nerve cells ended up being repressed, or turned off. In the majority of the old mice, nevertheless, the balance tipped to having mainly active nerve cells, and the neurons that were supposed to switch off when the tone was played in the presence of a noisy background failed to do so.
In addition, the scientists discovered that right before the tone hint, there was up to two times as much neuron activity in old mice than young mice, particularly among males, triggering the animals to lick the spout before the tone start.
A possible factor for that outcome, Kanold states, is that “in the old mice, the brain may be shooting or behaving as if a tone exists, when its not.”.
The explores ambient noise likewise revealed that young mice experienced shifts in the ratio of active to inactive neurons, while older mice had more regularly active neurons overall. Thus, young mice might reduce the results of ambient sound on neural activity while old mice might not, say the scientists.
” In older animals, ambient noise seems to make neuron activity more fuzzy, interfering with the ability to differentiate private sounds,” says Kanold.
On the advantage, Kanold thinks that due to the fact that of the mammalian brains flexible knowing capacity, it can be “taught” to address the fuzziness in older animals, consisting of people.
” There may be ways to train the brain to focus on private sound in the middle of a cacophony of sound,” he states.
Kanold notes that more research study is required to exactly map the connection between the inability to shut off particular nerve cells and hearing loss amid ambient noise, consisting of the brain circuits included and how they alter with age, as well as the prospective distinctions in between male and female animals.
Referral: “Decreased Modulation of Population Correlations in Auditory Cortex Is Associated with Decreased Auditory Detection Performance in Old Mice” by Kelson Shilling-Scrivo, Jonah Mittelstadt and Patrick O. Kanold, 7 December 2022, Journal of Neuroscience.DOI: 10.1523/ JNEUROSCI.0955-22.2022.
Other factors to the research are Kelson Shilling-Scrivo and Jonah Mittelstadt from the University of Maryland.
Funding for the research was offered by the National Institutes of Health (P01AG055365, RO1DC009607, RO1DC017785).
