Temporary blindness 'helps hearing'

Scientists in the US expect the findings could help those with hearing loss

Temporary blindness can improve hearing, a new study has shown.

Scientists have discovered that keeping mice in the dark for several days altered their brain circuit and made their hearing better.

Researchers now predict humans that humans will respond in the same way, because mammals have a similar brain structure in the region that controls these senses.

The phenomenon has been called the “Ray Charles effect,” as the soul singer and pianist was thought to have more sensitive hearing because of his blindness.

Researchers from the US reported in the journal ‘Neuron’ that neural connections in the brain that control vision and hearing work together to support the other sense.

The findings could be used to help people with hearing loss, and the distressing “ringing” in the ears known as tinnitus.

Dr Hey-Kyoung Lee, a leading member of the team from the Mind/Brain Institute at the Johns Hopkins University in the US, said: “In my opinion, the coolest aspect of our work is that the loss of one sense - vision - can augment the processing of the remaining sense, in this case, hearing, by altering the brain circuit, which is not easily done in adults.

"By temporarily preventing vision, we may be able to engage the adult brain to now change the circuit to better process sound, which can be helpful for recovering sound perception in patients with cochlear implants for example."

In the study, healthy adult mice were placed in a darkened environment for six to eight days, to simulate blindness, while their brain activity and response to sound was monitored.

When the mice were reintroduced to the light, their vision was unchanged, but their hearing was better than before.

As the researchers played a series of one-note tones, neurons in the auditory cortex involved in hearing fired faster and more powerfully than normal. They were also more sensitive to quiet sounds and better at discriminating between different sounds.

In addition the mice developed more nerve connections, or synapses, between the thalamus - a part of the brain that acts as a "switchboard" for sensory information - and the auditory cortex.

Co-author Dr Patrick Kanold, from the US University of Maryland, said: "We don't know how many days a human would have to be in the dark to get this effect, and whether they would be willing to do that. But there might be a way to use multi-sensory training to correct some sensory processing problems in humans."

After returning to normal lighting conditions the mice reverted to their usual standard of hearing in a few weeks.

In the next phase of their five-year study, the scientists plan to look for ways to make the sensory improvements permanent and to expand their scope beyond changes to individual neurons.

PA

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