The topic of neuroplasticity has been discussed on a number of Healthymemory Blog Posts including one specifically titled “Neuroplasticity.” A recent issue of New Scientist contained a report1 of one of the most remarkable examples of neuroplasticity. People who have lost their sight are learning to see with their ears.
This is not the first time that people have reported a kind of seeing through another modality. In 1969 the neuroscientist Bach-y-Rita rigged up a television camera to a dentist’s chair. A 20-by20 array of stimulators that translated images into tactile signals by vibrating against the participant’s back was positioned on the chair. This allowed blind participants to detect the presence of horizontal, vertical and diagonal lines. Skilled users could even associated the vibrations with faces and common objects. Bach-y-Rita continued to develop even more sophisticated devices that translated a camera’s images into electrical pulses delivered by a postage-stamp-sized array sitting on the tongue. After some practice users found that these pulses gave them a sense of depth and openness. They had a feeling that something was out there.
The latest device, named vOICe, uses sound rather than tactile stimulation. Peter Meijer thought of the idea in 1982, but it took until 1991 to build a desktop prototype. The user wears a pair of sunglasses mounted on a webcam that captures the scene in front of her. The image is sent to a computer that converts the picture into a series of sounds called a soundscape. The vOICe software scans across the scene from left to right converting each pixel into a beep. The frequency represents the vertical position of the pixel and the volume represents the brightness of the pixel. The soundscape is played into the user’s ears. Initially the brain’s auditory cortex tries to make sense of the soundscape. However, after ten to fifteen hours of training regions of the visual cortex begin to light up. So the data is being redirected to the part of the brain that interprets visual images. At about the same time that the visual cortex becomes active the users become more adept at understanding the soundscapes and recognizing objects. Of course, this is being done no where near as quickly at normal vision. However, users are able to see the environment and the experience is qualitatively similar to seeing. One user provided this description. “It’s like looking at a black-and-white movie from the 40’s. I can see the tree from top to bottom, and the cracked sidewalk.”
To this point the users have been individuals who once did see, but then lost their vision. So when they make statements that it is like seeing, it is related to past experience. The device is currently being tried by congenitally blind individuals. A key question is whether they can learn to use the device. If they can, this “seeing” will be a new experience for them.
This type of substitution should allow people to adjust to sensory losses. The capacity to recover lost functions is much greater than was formerly believed. This research shows that the ability to learn does not disappear as we grow older.
1Trivedi, B. (2010). Ear today, eye tomorrow. New Scientist, 14 August, 42-45.
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