In Marvel's Daredevil, blind lawyer-turned-vigilante Matt Murdock has enhanced hearing that helps him navigate his surroundings and fight bad guys, all because of a radioactive accident that happened to him when he was younger.
Now, fiction coincides with reality: multiple new studies reveal that blind people really do have better hearing.
The brains of people who were born blind or become blind early in life apparently rewire themselves to have more heightened musical abilities as well as to better track moving objects in space by sound, researchers said.
Measuring How Brains Of Blind People React To Sound
For years, scientists have wondered what particular changes in the brain might underlie enhanced auditory abilities among visually impaired people. For the first time, scientists explain these hearing improvements in a pair of research papers.
Both studies use functional MRIs to identify two differences in the brains of blind individuals that might explain how they navigate auditory information, but instead of just looking to see which parts of the brain were most active while listening, researchers examined the sensitivity of the brain when it comes to detecting subtle differences in audio frequency.
"We weren't measuring how rapidly neurons fire, but rather how accurately populations of neurons represent information about sound," said Kelly Chang, an author of one of the studies.
Blind People Have Better Hearing
One of the studies found that in the auditory cortex, blind individuals showed narrower neural "tuning" than non-visually impaired people when it comes to discerning small differences in sound frequency.
The auditory cortex is the area of the brain that receives very similar information among blind and sighted people. Among blind people, more information needs to be extracted from sound, and so the auditory cortex appears to have developed more enhanced capacities, explained Professor Ione Fine, a senior author on both of the studies.
The second study examined how the brains of people who were born blind or became blind early in life represent moving objects in space.
Researchers found that an area of the brain known as the hMT+ showed neural responses that reflect the motion and frequency of auditory signals among blind people. This means that the hMT+ plays a huge role in tracking moving objects or footsteps of people, scientists said.
The research team also examined two individuals who had been blind from infancy until adulthood but their sight got restored via surgery. In these two individuals, the hMT+ appeared to serve a dual purpose, which meant that they were capable of processing both auditory and visual information.
Implications Of The Study
Known as the Doppler effect, sound has the ability to change pitch thanks to a relative change in frequency of the sound waves. This phenomenon happens in an ambulance or police siren.
When blind people are attuned to the subtle differences in everyday noises, it may help them interpret their surroundings, researchers said.
Chang explained that among people with sight, an accurate representation of sound is not as important as compared to blind people, who use it to recognize objects. Such findings help scientists understand the kind of changes that occur in the brain that help blind people identify sounds in the environment.
Furthermore, the inclusion of two blind people whose sight were recovered in the study offers evidence that plasticity in the brain occurs early in development. The results reveal that the brains adapted to auditory processing because of early life blindness, but the abilities were maintained even after sight was restored.
The pair of research papers have been published in the Proceedings of the National Academy of Sciences and the Journal of Neuroscience, respectively.
Photo: Travis Isaacs | Flickr