Minimizing sight for as little as a week can improve the brain’s ability to processs hearing, say neuroscientists at John Hopkins University. The findings, published in the journal the Neuron, could help patients with hearing loss to regain a level of hearing.
According to researchers, sensory systems do not work in isolation: instead, they show interactions that are specifically uncovered during sensory loss.
Using mice, the research team analysed the neural connections in the brain that manage vision and hearing to explore how the connections worked together to support each sense.
Temporary blindness proved to change perception of pitch and loudness by altering the circuitry of the “primary auditory cortex” – the part of the brain that processes sound.
Hey-Kyoung Lee, associate professor of neuroscience and researcher at John Hopkins University, 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 monitoring the neural activity in the brains of mice in response to sound, scientists made the discovery that simulated blindness can emhance the connections supporting hearing.
One group of mice were kept in a darkened environment to simulate blindness for a week. The group showed signs of altered brain chemistry in comparison to a second group that were kept in a naturally-lit environment.
Hey-Kyoung Lee, Ph.D, adds:
Our result would say that not having vision allows you to hear softer sounds and better discriminate pitch. If you ever had to hear a familiar piece of music with a loud background noise, 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. Our work would suggest that if you don’t have vision you can now rescue these ‘lost’ notes to now appreciate the music as is.”
According to the findings, “thalamocortical inputs” – a set of connectors in the primary sensory areas of the brain, become less flexible as we age. However, when another sense is impaired, these connectors can be reactivated to support the sense that is affected.
Dr Kanold of The University of Maryland – a supporting university in the research, is hopeful that the study’s findings will be applicable 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.” Dr Kanold
The changes identified by the group were reversible – the hearing of the mice that experienced simulated blindness reverted to pre-experiment levels following a few weeks in a naturally-lit environment.
The research project will continue for the next five years. The future studies into hearing and vision will look at ways of making permanent sensory improvements; looking beyond individual neurons to study broader changes in the way the brain processes sounds.
John Hopkins Press Release: Simulated Blindness Can Help Revive Hearing Loss, Researchers Find