The Hearing of the Blind

We've known that the brains of people born blind or who lost their vision in childhood have adapted by enhancing their sense of hearing. But we didn't know exactly how until two recent studies pinpointed actual changes in the brain.

One key difference between blind and sighted is in the auditory cortex of the brain where sound is processed and where we comprehend speech and language. People who are blind are more sensitive to sound. Scientists found they can more accurately discriminate the frequency of tones and detect small changes in pitch better than sighted people when they heard the same sound.

The main reason for this is they have to extract more information from that sound than people who can see. In another study, scientists learned that the blind process the movement of objects in the same area of the brain where sighted people visually track moving objects. This is the hMT+ region and instead of using sight to track movement, it adapted to using sound instead. This allows them to track traffic and people around them.

By comparison, sighted people didn't have enough neural activity to track movement using sound. Their brains just weren't developed to use sound as well as the blind have adapted to do. These studies begin to identify how the brain uses sound to provide important environmental information. It's another example of the adaptability of our complex bodies.