Researchers at Hebrew University in Jerusalem are developing a sonar-based device that, according to preliminary tests, already allows the congenitally blind to distinguish between different shapes and even to read. Just as shockingly, the device appears to activate areas of the brain that were formerly believed to be permanently damaged in such people.
“These results suggest that it may be possible, with the right technology and rehabilitation, to ‘wake up’ certain areas of the brain and access certain aspects of the visual world, even after … a lifetime of blindness,” researcher Laurent Cohen said.
The device was recently tested by a team of researchers from Hebrew University, the ICM Brain and Bone Marrow Institute Research Center, and NeuroSpin. The findings were published in the journal Neuron.
The sonar device is specifically designed for people who have been blind from birth. Known as a “sensory substitution device,” it consists of a small video camera mounted on a pair of glasses and connected to a laptop or smart phone. The camera transmits information to the computer, which then converts the visual images into specific sounds and relays them to a set of headphones worn by the user. Each type of image corresponds to a certain sound; for example, an oblique line would be rendered as an increasingly high or low-pitched sound. This system allows the device to convert even complex images into auditory packages.
The researchers found that after only 70 hours of training with the device, congenitally blind users were able to correctly distinguish between different types of images, such as faces versus houses. They were also able to correctly identify people’s locations and even read letters and words. The degree of visual detail that users were able to perceive was such that a sighted person who could see such detail would not be categorized as blind by the World Health Organization.
Reactivating the visual cortex
The researchers also used functional MRI scans to examine what occurred in the brain during use of the device. They found that the areas of the cerebral cortex associated with visual perception became highly active when users listened to auditory representations of visual cues.
Scientists had previously assumed that these regions of the brain simply fail to develop in the congenitally blind.
It’s not just the overall visual cortex that becomes active, either. In people with normal vision, for example, a specific region of the visual cortex in the brain’s left hemisphere, known as the VWFA, becomes much more active when people look at a string of letters than when they look at anything else. This exact same differential response was seen in patients using the sensory substitution device.
The findings support the hypothesis that what the visual cortex actually does is analyze shapes, and that it can perform this task based on any kind of sensory input.
“The fact that this specialization for reading develops after just a few hours of training shows a remarkable degree of cerebral plasticity,” researcher Stanislas Dehaene said.
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