The blind can’t see with their eyes, but they can see with their “mind’s eye” if they are able to activate it through sounds and sensory substitution devices (SSDs). Researchers at the Hebrew University of Jerusalem and colleagues in France have just published an article on this in the prestigious neuroscience journal Neuron.
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Common wisdom has it that if the visual cortex in the brain is deprived of visual information in infancy, it may never develop its functional specialization properly, making sight restoration later in life almost impossible.
But researchers have found that congenitally blind people who use specialized photographic and sound equipment can actually “see” and describe objects and even identify letters and words.
“Reading with Sounds”
The study by Prof. Amir Amedi of HU’s Edmond and Lily Safra Center for Brain Sciences and the Institute for Medical Research Israel-Canada, and doctoral candidate Ella Striem-Amit, demonstrated how this achievement is possible through the use of a unique training paradigm using SSDs.
The article, titled “Reading with Sounds: Sensory Substitution Selectively Activates the Visual Word Form Area in the Blind,” was written with help from Prof. Laurent Cohen and Prof. Stanislas Dehaene of Pierre and Marie Curie University’s faculty of medicine, INSERM and the College of France in Paris.
These are non-invasive sensory aids that provide visual information to the blind via their existing senses. For example, with a visual-to-auditory SSD in a clinical, or everyday setting, users wear a miniature camera – connected to a small computer or smartphone – and stereo headphones.
The images are converted into “soundscapes,” using a predictable algorithm, allowing the user to listen to and then interpret the visual information coming from the camera.
The blind participants using this device reach a level of visual acuity technically surpassing the criterion set by the World Health Organization for blindness – as published in a previous study by the same group.
“Hearing” facial expressions
The study shows that following – a dedicated but relatively brief – 70 hours of unique training paradigm, developed in the Amedi lab, blind people could easily use SSDs to characterize images into object categories, such as of faces, houses, body shapes, everyday objects and textures.
They could also identify even more complex everyday objects – locating people’s positions, identifying facial expressions, and even reading letters and words.
The study went on further to actually test what happens in the brain when the blind learn to see with sounds.
Specifically, the group tested the ability of this high-acuity vision to activate the supposedly dormant visual cortex of the blind, even though it was taught to process the visual images through sounds only in adulthood.
The team used functional magnetic resonance imaging to measure the neural activity of people blind from birth as they “saw” – using the SSD – high-resolution images of letters, faces, houses, everyday objects and body-shapes.
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Via the Jerusalem Post
Photo by the Hebrew University of Jerusalem
