Short stays in darkness can boost hearing, study shows

Date: Feb-06-2014Music experts often say that blind performers like Ray Charles and Stevie Wonder are

good examples of how not being able to see can enhance one's ability to hear. Now, a new neuroscience study appears to support this - it found preventing sight for as little

as a week may be enough to help the brain process sound more effectively.

Writing in the journal Neuron, researchers from Johns Hopkins University and the

University of Maryland describe how they explored the relationship between vision and hearing

in the brains of mice.

They found that connections in the part of the brain that controls vision and hearing work

together to boost each sense, and they hope their findings will help people experiencing hearing loss

to get some of it back.

One of the researchers, Hey-Kyoung Lee, an associate professor of neuroscience at Johns

Hopkins, says:

"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," she adds, "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."

Hey-Kyoung Lee briefly explains the findings of their study in the video below:

Mice kept in dark had alterations in brain's hearing circuits

For their study, the team used two groups of healthy mice. They kept one group in complete

darkness for a week, and the other group stayed in a naturally lit environment. They then

exposed the mice to a range of sounds and compared their brain activity and responses.

They found the mice that had undergone a week of simulated blindness had alterations in brain

circuits in the primary auditory cortex, a part of the brain that allows conscious perception of

pitch and loudness.

The researchers write:

"... we show that visual deprivation leads to improved frequency selectivity as well as

increased frequency and intensity discrimination performance of A1 [primary auditory cortex]

neurons."

Prof. Lee says this would indicate that not having vision might allow a person to hear softer

sounds and discriminate pitch more effectively.

"If you ever had to hear a familiar piece of music with a loud background noise," she

explains, "you would have noticed that sometimes it seems the beat or the melody is different,

because some of the notes are lost with the background."

She says their findings suggest that if you do not have vision, then perhaps you can restore these

"lost" notes and appreciate the music as it really is.

Hearing-related brain connections may be reactivated

From their results, the team concludes that our "thalamocortical inputs" - a set of

connectors in the primary sensory areas of the brain - become less flexible with age. But they

can be reactivated when another sense is impaired.

Another of the researchers, Patrick Kanold, a biologist at the University of Maryland, says

they are 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. But there might be a way to use multi-sensory training

to correct some sensory processing problems in humans."

The team found the changes were reversible: the simulated blind mice went back to hearing

normally after a week in a normally lit environment.

The team is continuing their 5-year study. The next step will be to look at how to make

the hearing boost permanent, after which the researchers want to examine how preventing vision

to boost hearing might affect the brain more broadly.

Funds from the National Institutes of Health helped finance the study.

In December 2013, Medical News Today reported that researchers from the University

of Michigan Medical School found how hyperactive brain cells may hold a key to tinnitus

treatments. Writing in the Journal of Neuroscience, they describe finding that a

process called stimulus-timing dependent multisensory plasticity is altered in animals with

tinnitus.

Written by Catharine Paddock PhD




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