Some blind people are able to use the sound of echoes to "see" where things are and to navigate their environment. Now, a new study finds that these people may even be using visual parts of their brains to process the sounds.
The study finds that in two blind men who can echolocate, brain areas normally associated with vision activate when they listen to recordings of themselves echolocating.
To study EB and LB's echolocation abilities, the researchers recorded their clicks and echoes as they sat near an object (in this case, a screen). The researchers then played those clicks and echoes back as the men lay in a functional magnetic resonance imaging (fMRI) machine. The fMRI measures blood flow to different areas of the brain, providing a real-time look at brain activity.
The researchers found that as the men listened to the echoes, the primary visual area of their brains, known as the calcarine cortex, became more active. When the researchers played sounds with echoes and sounds without echoes, they found that the blind men's calcarine cortex responded based on the presence of echoes, while the auditory cortex, used to process sounds, did not respond differently either way.
The same tests performed on two sighted men without echolocation abilities turned up no such calcarine cortex activity.
Blind people often show reorganized brain processing compared with their sighted counterparts, so more research is needed on larger groups of people to tease out exactly what's going on in the brain, the researchers wrote. Ideally, researchers may be able to compare not just blind echolocaters and sighted non-echolocaters, but also blind people who don't echolocate and sighted people who do.
According to study researcher Stephen Arnott of the Rotman Research Institute in Toronto and his colleagues, the study is a first step in understanding how the brain processes an ability that seemingly melds sound and sight.
"There is the possibility that even in sighted people who learn to echolocate, visual brain areas might be recruited," Arnott said in a statement.
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