Being in dark seems to help those suffering hearing loss

A new report suggests it might be possible to change the circuitry of the brain to better process sound, a finding that could give renewed hope to the 350 million people worldwide who suffer from hearing loss.  

Patrick Kanold, an expert on how the brain processes sound and co-author of the new study published in Neuron, says a child’s brain is malleable enough to rewire some circuits that process sensory information.  

“We were interested if, at older ages, we can also coax the brain to change,” he said. 

To try to do that, the University of Maryland biologist and colleagues from Johns Hopkins University used a reversible technique to simulate blindness by keeping mice with normal vision and normal hearing in complete darkness for a week.  

“We want to know if the deprivation of vision changed the way you hear,” Kanold said.  

At the end of the week, the mice were put in a sound-proof chamber and subjected to a series of one-note tones to test their hearing. The scientists then measured the neural response.

“And we found that they hear better and that connections in the brain had changed,” Kanold said. “It surprised us because during this age, if you would alter the auditory experience of mice, the hearing would not change, but we found if you deprive them of vision, the hearing did change.”

The adult mice developed more neural connections, and could better discriminate among pitches and hear softer sounds.  

“These tones could not be distinguished by mice that were raised normally, but could be distinguished by animals that were sitting in the dark,” Kanold said. “So they got much better distinguishing these very close by frequencies.”  

Kanold says while the rodents’ sharper hearing reverted back to normal within a few weeks, the experiment demonstrated the adult brain may be less hard-wired than previously thought. By temporarily preventing vision, Kanold says, it may be possible to change the brain circuitry to better process sound.  

The next step for the researchers is work on making those changes in hearing last longer. Kanold says what they find could lead to treatments for people.

“This approach potentially might be useful for humans, where the peripheral hearing is fine, but where the central processing of sound stimuli is altered,” he said.

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