How the blind are helping us understand the brain
Scientists are rethinking the conventional view that the brain is divided into sensory 'regions.'
Humans didn't always read, write and do arithmetic.
Thousands of years ago, before the advent of numbers and letters, humans were a much more primitive species. Their brains, however, were structured pretty much the same as they are now.
So why do modern diagrams of the brain designate certain regions for activities like reading and numbers? And furthermore, how does this apply to people who lack function in one or more of their senses, like sight or hearing? Do the "visual" regions of the brain lay dormant in blind people, for example?
These questions have puzzled scientists for years. Now, a group of researchers at the Hebrew University of Jerusalem says the answers lie in the brains of the blind.
In a study published recently in the journal Nature Communications, Professor Amir Amedi and his colleagues assert that traditionally accepted sensory regions of the brain – the visual cortex for sight, for example, as well as the auditory cortex for sound – are not activated by people's ability to see or hear. In other words, these regions work in response to the activity itself, not the sense that's used to achieve it.
This latest paper is a new avenue in an ongoing study at Hebrew University that's examining ways to help the blind "see" colors and shapes. Last year, Amedi and his colleagues at the school's Center for Human Perception and Cognition used a tool called a sensory substitution device (SSD) to help visually impaired people receive information about their environment. This device basically puts a "soundscape," which is an auditory cue that allows a subject to interact with objects they can't see, in place of an image. In one demonstration, a person was blindfolded and given these cues, and using the soundscape, was then able to decipher which apple, in a plate of red and green apples mixed together, was red.
"On the surface, it seems like vision works a little bit like a camera, and indeed there are many similarities. The lenses, the shutter in the iris, and so on and so forth," Amedi said in a TEDxJerusalem talk. "But it's actually a little bit more complicated. We see with our brain not less than we see with our eyes."
Knowing this, Amedi reasoned that most blind people are blind because of a problem with their eyes, not with their brains. "So what if we found a bypass to deliver the visual information in their brain?"
That "bypass" idea, he said, was the genesis of the SSD concept. After seeing that blind people could actually be "trained" to use SSDs, he then looked deeper into what parts of the brain they were using to process that information.
Dr. Amir Amedi demonstrates the EyeCane, a device he developed that uses an algorithm to translate distance into sound and vibrations. (Photo: Eyal Toueg/Amedi Lab)
In the Nature Communications paper, researchers used MRI scans to show that the same brain regions traditionally dedicated to vision are, in fact, being used by blind people – only they're "seeing" using sounds. "These regions are preserved and functional even among the congenitally blind who have never experienced vision," lead researcher Sami Abboud said.
So what does all this mean for the future of brain studies?
"Beyond the implications for neuroscience theory, these results also offer us hope for visual rehabilitation," Amedi said. "They suggest that by using the right technology, even non-invasively, we can re-awaken the visually deprived brain to process tasks considered visual, even after many years of blindness."
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