How hearing loss damages memory

Christiane Fux studied journalism and psychology in Hamburg. The experienced medical editor has been writing magazine articles, news and factual texts on all conceivable health topics since 2001. In addition to her work for, Christiane Fux is also active in prose. Her first crime novel was published in 2012, and she also writes, designs and publishes her own crime plays.

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The phenomenon is well-known: When hearing deteriorates in old age, the risk of developing dementia or other mental impairments increases. Experiments with mice show: The reason for this is apparently disturbances in signal transmission in the brain. The hippocampus is particularly affected: the region of the brain that is the gateway to our memory.

Missing stimuli from the auditory nerve

"Our results offer new insights into the presumed cause of the connection between cognitive decline and age-related hearing loss in people," says Prof. Denise Manahan-Vaughan from the Ruhr University Bochum (RUB).

Her team of neuroscientists examined mice that were born with intact hearing, but gradually lost their hearing due to a genetic defect. They thus provide a good model for senile hearing loss in humans.

Adaptability of the brain suffers

The researchers found changes in the animals' hippocampus - a brain region that is crucial for memory formation. In contrast to mice without the genetically preprogrammed hearing loss, the distribution and density of the receptors to which certain messenger substances dock in this area are constantly changing.

How smoothly this happens affects how well a signal is transmitted from one nerve cell to another. In the hippocampus, this is what determines the memory in humans and animals.

How learning works

During learning processes, the number of receptors between the nerve cells involved increases. The transfer of information is thus increasingly strengthened. These and other processes with which the brain reacts to the influence of stimuli are called synaptic plasticity by neurologists. It is the prerequisite for learning and memory formation.

The synaptic plasticity enables the long-term storage of experiences and the retention of memories.

Plasticity is lost

This ability is increasingly waning in people with dementia. First of all, new memory contents are affected. Apparently the weaker and weaker signals from the auditory sense disrupt the normal expression of the receptors in the hippocampus.

In contrast to mice without the genetically pre-programmed hearing loss, the synaptic plasticity of the animals was chronically impaired by progressive hearing loss. The distribution and density of neurotransmitter receptors in sensory and memory regions of the brain also changed constantly.

At the same time, the researchers were able to show that the animals' memory deteriorated increasingly.

Quicksand in the brain

The researchers believe that the constantly changing availability of the receptors hinders information processing. “This creates a kind of quicksand that prevents the hippocampus from working effectively,” says Denise Manahan-Vaughan.

Compensate for hearing loss as early as possible

The study emphasizes that it is important for mental health to compensate for hearing loss as early as possible - for example with a hearing aid. There is another important argument for this: the brain forgets how to process the individual frequencies if the signals are absent for too long. This cannot be compensated for later with a hearing aid. So you shouldn't wait until you have very poor hearing before going to the hearing care professional.

Experts estimate that around 14 million people suffer from a hearing loss that requires treatment. In addition to age-related hearing loss, these also include noise-related hearing loss and congenital hearing disorders. According to the 2018 EuroTrak study by the Swiss market research company Anovum, only 37 percent of those affected wear hearing aids.

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