Scientists have often linked age-related hearing loss to hair cells in the inner ear.
They believe that damage to these cells over time is associated with hearing impairment in people.
Recently, however, a study published in the Journal of Neuroscience suggests that hearing loss in older people is closely linked to the brain, and that
An excess of active neurons may make it difficult for older mice to discriminate between sounds in noisy environments.
The researchers recorded the activity of 8078 neurons in the auditory cortex of the brains of 12 older mice (16-24 months) and 10 younger mice (2-6 months).
First, the scientists trained the mice to lick the nozzle when they heard a certain tone, and then added white noise to this and continued to train the mice to lick the nozzle.
As a result, older mice performed similarly to younger mice before the addition of white noise.
After the addition of white noise, the older mice were significantly less able to distinguish sound than the younger mice.
To assess the direct performance of mouse neurons in the hearing test, the researchers used two-photon imaging techniques to look at the auditory cortex.
Normally, when an individual hears a tone, some neurons in the brain that work normally in a noisy environment will have increased activity, while the activity of other neurons will be inhibited or shut down.
However, in the auditory cortex of the aged mice participating in the experiment, there were more active neurons and some neurons that should have been turned off in the noisy environment were not turned off.
The ratio of active to inactive neurons was different.
The researchers believe this is the reason why young mice can suppress the effects of environmental noise on neural activity while older mice cannot.
However, the scientists also noted that because the mammalian brain has the ability to learn, it is still possible for older individuals to be trained to solve the problem of distinguishing each sound in a noisy environment.