Short stay in darkness may actually heal hearing

Written by PTI | Washington | Updated: Feb 6 2014, 21:55pm hrs
Minimising a person's sight for as little as a week may help improve the brain's ability to process hearing, scientists say.

Hey-Kyoung Lee at the Johns Hopkins University and colleagues examined the relationship between vision and hearing in the brain and found that simulated blindness can help revive hearing.

Music experts often cite blind musicians Stevie Wonder and Ray Charles as examples of how a lack of sight can heighten or enhance hearing, researchers said.

Lee and colleagues conducted experiments on mice to find how neural connections in the brain area that manages vision and hearing work together to support each sense.

These findings could help those experiencing hearing loss regain more use of that sense, researchers 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," Lee said.

"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," she said.

In their experiments, the researchers placed healthy adult mice in a darkened environment to simulate blindness for about a week and monitored their response to certain sounds.

Those responses and brain activity were then compared to a second group of mice that were in a traditional, naturally lit environment.

The researchers found a change in the brain circuitry for the mice that experienced simulated blindness, specifically in the area of the brain that processes sound, called the primary auditory cortex.

The primary auditory cortex allows conscious perception of pitch and loudness.

"Our result would say that not having vision allows you to hear softer sounds and better discriminate pitch," said Lee, an expert on how the brain processes vision.

The researchers concluded that a certain set of connectors in the primary sensory areas of the brain, called thalamocortical inputs, are less flexible in humans later in life.

When another sense is also impaired, however, those connectors can be reactivated to support the sense that is lagging.

Biologist Patrick Kanold at the University of Maryland, College Park, who co-authored the study published in the journal Neuron, is hopeful that the findings will apply to humans.

"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," Kanold said.

"But there might be a way to use multi-sensory training to correct some sensory processing problems in humans," he said.