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Blind People’s Brains Rewire Themselves to Enhance Other Senses

New study finds marked differences between the brains of blind and sighted people

Scientists used this MRI scanner to compare the brains of blind and sighted people. (Boston University Medical School Center for Biomedical Imaging)
smithsonian.com

It’s scientific canard so old it’s practically cliché: When people lose their sight, other senses heighten to compensate. But are there really differences between the senses of blind and sighted people? It’s been hard to prove, until now. As George Dvorsky reports for Gizmodo, new research shows that blind people’s brains are structurally different than those of sighted people.

In a new study published in the journal PLOS One, researchers reveal that the brains of people who are born blind or went blind in early childhood are wired differently than people born with their sight. The study is the first to look at both structural and functional differences between blind and sighted people.

Researchers used MRI scanners to peer at the brains of 12 people born with “early profound blindness”—that is, people who were either born without sight or lost it by age three, reports Dvorsky. Then they compared the MRI images to images of the brains of 16 people who were born with sight and who had normal vision (either alone or with corrective help from glasses).

The comparisons showed marked differences between the brains of those born with sight and those born without. Essentially, the brains of blind people appeared to be wired differently when it came to things like structure and connectivity. The researchers noticed enhanced connections between some areas of the brain, too—particularly the occipital and frontal cortex areas, which control working memory. There was decreased connectivity between some areas of the brain, as well.

When it came to how the brain worked, it appeared that blind people’s brains communicated differently than their sighted counterparts. Most notably, the occipital cortex—the part of the brain that’s usually used for visual processing—seemed to have been repurposed to process other sensory input like smell and sound instead. “In blind people, the occipital cortex is not processing visual information, but it’s still working,” writes Dvorsky, “—and in way that could explain why blind people experience a heightening of the senses.”

Researchers say that these dramatic differences are a result of neuroplasticity—the ways in which the human brain adapts and changes itself in response to different conditions. “These connections that appear to be unique in those with profound blindness suggest that the brain 'rewires' itself in the absence of visual information to boost other senses,” they say in a press release.

The paper doesn’t discuss why or how those changes occur—just that they appear to have occurred. But the work is an important first step in figuring out how blind people’s brains work around the lack of visual input.

Now that it’s clear that there are big differences between blind and sighted brains, researchers can try to figure out which tasks affect sensory connectivity and use that information to develop therapies that help blind people compensate even more for the lack of visual input. They’ll also need to compare the scans with those of people who lost their sight later in life.

Though the sample size was small, the new research opens up plenty of intriguing possibilities for future research—and the hope that a better understanding of the way blind people’s brains are wired can help make blind people’s lives easier in the long run.

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