Staying in Darkness could Improve Hearing

A team of researchers has shown that temporary blindness may boost hearing. The study could help understand the connection between various brain regions and how it could be used to treat hearing loss in people.

The study, by researchers at University of Maryland and Johns Hopkins, found that hearing ability could be improved in adult mice.

"There is some level of interconnectedness of the senses in the brain that we are revealing here," Patrick Kanold, an associate professor of biology at UMD said in a news release.

"We can perhaps use this to benefit our efforts to recover a lost sense," said Hey-Kyoung Lee, an associate professor of neuroscience at JHU. "By temporarily preventing vision, we may be able to engage the adult brain to change the circuit to better process sound."

It is known that young brains are quite flexible and learn things quickly. In the present study, researchers wanted to know whether adult brains could be coaxed into rewiring.

For the research, Lee and colleagues placed mice with normal vision and hearing in darkness for six-eight days.

The team found that the mice had developed an acute sense of hearing, but their vision remained the same.

The mice were then put under a brain scanner. Researchers then played one-note tones and saw which neurons fired in response. They focused on the auditory cortex that is associated with hearing.

Specifically, they looked at neurons in the middle section of the auditory cortex called the thalamocortical recipient layer, which receives signals from the thalamus and acts as a switchboard for the sensory signals. Previously, researchers believed that the thalamocortical wasn't flexible in adults.

In the study, researchers found that the test mice showed an increased activity in this 'switchboard region,' meaning that they could hear better than before.

"This makes me hopeful that we would see it in higher animals too," including humans, Kanold said in a news release. "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 mice in the study returned to normal hearing within few days. Researchers want to see if they can make these sensory changes permanent.

Dr Michael Akeroyd, from the Medical Research Council's Institute of Hearing Research, in Glasgow, told the BBC: "I thought, 'Ooh this is interesting.' I don't know if it's practical, but it's got potential."

He added that the research doesn't mean we'll see old people be put in dark to reverse their hearing loss. However, the study shows that hearing is more complex than assumed, according to BBC

The study is published in the journal Neuron.