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Extraordinarily gifted blind musicians such as Ray Charles and Stevie Wonder are often cited as examples of how losing sight is sometimes compensated with extraordinary hearing. Neuroscientists now believe they know the reasons why.

Neuroscientists have discovered that restricting a person's sight for as little as a week may improve the brain's ability to process sound.

Dr. Hey-Kyoung Lee, researcher at the Zanvyl Krieger Mind/Brain Institute and an associate professor of neuroscience at the Johns Hopkins University, collaborating with biologist Patrick Kanold at the University of Maryland at College Park and three other scientists, recently published a paper on the relationship between hearing and vision in the brain in the journal Neuron

In a series of experiments using mice, Lee, Kanold, and other researchers discovered how the neural circuits that support hearing and sight work together to support each sense, and to maximize sensory inputs when one or the other of the two senses is deficient.

The scientists placed healthy adult mice in a darkened (although not completely dark) environment for a week and observed their brain activity and behavioral responses to certain sounds. They then compared the brain activity and behaviors of the test mice to a those of a control group of mice that had been kept in normal light conditions.

The researchers found that time in darkened conditions changed the circuitry in a region of the brain known as the primary auditory cortex, which enables perception of pitch and loudness.

“Our result would say that not having vision allows you to hear softer sounds and better discriminate pitch,” Dr. Lee said in a Johns Hopkins University press release.

The researchers also found that deafening, placing the mice in a very quiet environment, increased the strength of neural circuits in the visual cortex. When the mice were deprived of sound, their vision became more acute.

How would these findings apply to humans?

Dr. Lee gave the example of trying to listen to a familiar song over a lot of background noise. Dur to the background noise, some of the notes and some of the rhythms may be lost. It may be possible to hear the melody but not the harmony, or it may not be possible to feel the rhythm due to the interference of ambient sound.

With our eyes closed, however, it is easier for us to hear the notes, feel the rhythms, and understand the words. And in people who don't have vision, such as the famous musicians Stevie Wonder and Ray Charles, "lost notes" can be found with far greater ease than by sighted people.

Most of us lose some of our sensitivity to sights and sounds later in life, even if our eyes and ears are in good shape. The connections between the thalamocortical inputs in our brains are less flexible when we are adults than they were when we were children. But deprivation of one of our senses can restore these circuits so that the brain is able to devote more attention to one sense than another.

Dr. Kanold stated in a Johns Hopkins University press release that he does not know how long a human would have to stay in a darkened room to have heightened sound perception. or if many people would be willing to try. The effect in mice is reversible when they return to normal-light conditions, Kanold said.

Continue reading after recommendations

  • Petrus E, Isaiah A, Jones AP, Li D, Wang H, Lee HK, Kanold PO. Crossmodal induction of thalamocortical potentiation leads to enhanced information processing in the auditory cortex. Neuron. 2014 Feb 5
  • 81(3):664-73. doi: 10.1016/j.neuron.2013.11.023. PMID: 24507197.
  • Voss P. Sensitive and critical periods in visual sensory deprivation. Front Psychol. 2013 Sep 26,4:664. eCollection 2013.
  • Photo courtesy of PublicDomainPictures by Pixabay :
  • Photo courtesy of Ben Churchill by Flickr :

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