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  February 20, 2013
Sight Seeing

Sonar Vision System Helps Blind to 'See'

By Eye² Staff

A "sonar vision" system that enables people who are blind from birth to perceive the shape of a face, a house or even words and letters, is being developed by a team at the Hebrew University of Jerusalem, according to an article published on the website of CEA, the French Alternative Energies and Atomic Energy Commission. Using this device, the researchers have shown that, in people who are blind from birth, the areas of the cerebral cortex normally devoted to reading become activated in response to stimulation. The results of this study, conducted in conjunction with researchers at the ICM Brain and Bone Marrow Institute Research Center (Inserm/UPMC/AP-HP) and NeuroSpin (CEA-Inserm), were published in the research journal Neuron on November 8, 2012.

The sonar device consists in a small video camera embedded in a pair of eyeglasses, a laptop (or smartphone) which transforms images into sounds, and stereo headphones to hear the sounds produced. For example, an oblique line is transformed into an increasingly high-pitched sound (or increasingly lower-pitched sound). The same principle is used to encode much more complex images in auditory form. Using this system, the blind can achieve greater "visual" acuity than that defined as blindness according to WHO (World Health Organization) criteria, the CEA said. After only 70 hours of specialized training, the blind are able to correctly classify images into different categories (faces, houses, etc.). They can also perceive other important information, such as where people are located in a room and certain facial expressions. They can even read words and letters (see videos). In addition to the performance enabled by this sensory substitution system, the researchers at the Hebrew University wanted to understand what happens in the brain when a blind person learns to "see" through sound. To this end, they have developed a functional MRI study based on a specific paradigm. In particular, they have shown that the regions of the cortex normally devoted to visual perception, which seem to serve no apparent use in the blind, become highly activated in response to the "sonar vision" of faces, houses and words, etc. Not only is the visual cortex activated, it also demonstrates a "normal" functional selectivity of different categories of objects. Thus, in a sighted person, a very specific region of the visual cortex in the left hemisphere (known by the acronym VWFA), is known to become more activated when perceiving a string of letters than when perceiving any other kind of object. It is exactly this same region that is activated when a blind person reads letter using the "sonar vision" device.

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