Studies have found that people born blind or who became blind during childhood typically have a better sense of hearing than sighted people. But why? New research may explain the reasons behind this.
In one study by neuroscientists at the University of Washington, researchers found that individuals who are blind show narrower neural “tuning” in their auditory cortexes than sighted people. This then seems to make them more adept at discerning small differences in sound frequency (Huber: 2019).
According to Ione Dine, a senior author on the study, “This is the first study to show that blindness results in plasticity in the auditory cortex. This is important because this is an area of the brain that receives very similar auditory information in blind and sighted individuals...But in blind individuals, more information needs to be extracted from sound -- and this region seems to develop enhanced capacities as a result.”
She continued: "This provides an elegant example of how the development of abilities within infant brains is influenced by the environment they grow up in (University of Washington: 2019)."
In a further study, the same researchers then sought to understand how people born blind or who became blind during childhood represent moving objects in space. Measuring neural responses in study participants via an fMRI machine as they listened to tones with different frequencies that sounded as though they were moving, they found that in blind people, the hMT+ region (an area of the brain responsible for tracking moving visual objects in sighted people) produced neural activity whereas in sighted people, it remained more or less inactive.
The study also included two people who, although were blind as children, had their sight restored in adulthood. For them, the study found that the hMT+ regions in their brains served a dual purpose, with the ability to process both auditory and visual motion. For the researchers, these findings taken together demonstrate that plasticity in brain regions occurs early in development, as well as the ability of the brain to repurpose parts of the brain that would otherwise remain unuseful (ibid.).
According to Fine, “These results suggest that early blindness results in visual areas being recruited to solve auditory tasks in a relatively sophisticated way.” She further added that this research expands current knowledge about how the brain develops and how blind people make sense of the world.
Huber, Elizabeth: JNeurosci