using the tongue to give sight to the blind -- 10/13/15

Today's selection -- from The Brain's Way of Healing by Norman Doidge, M.D. Using a blind person's tongue -- along with the neuroplasticity of the brain -- to enable them to see:

"Kurt [Kaczmarek, Ph.D.] spent twenty-five years learning how to produce synthetic electrical signals that can carry complex information that can be inputted into the skin's touch receptors, then relayed to the brain. ... He constructed a device that supplied visual information from a camera to the tongue, then to the brain, allowing blind people to see (described in The Brain That Changes Itself). They learned to present the information on the tongue using an array of 144 electrodes and found ways to coordinate the firing sequences of electrodes in wavelike patterns. ...

"Kurt ... is probably the world's leading expert on how to use electrical stimulation to speak to the brain through the human skin, a process he calls 'electro-tactile stimulation.' His long-term project is to use all he's learned to develop guidelines for making electro-tactile devices. ... 'I mean,' he says, 'people are coming in here with a cane and then walking out without one.' ...

"Against the wall of Yuri's small office sits the one cane they have kept, the first that was left behind in this tiny lab. It belonged to Cheryl Schiltz, who came to the lab after being disabled for five years and went home actually dancing. Yuri's office once belonged to the group's founder, Dr. Paul Bach-y-Rita. The story of how Cheryl recovered, and of Bach-y-Rita's own realization that the brain is plastic, was driven by a very personal experience, which I told in detail in The Brain That Changes Itself.

"In 1959 [Dr. Paul Bach-y-Rita]'s sixty-five-year-old father, Pedro, had a stroke that paralyzed his face and half his body and left him unable to speak. The doctors told Paul's brother George that Pedro had no hope of recovery. George, a medical student, was still too early in his medical studies to have learned the doctrine of the unchanging brain. So he began treating his father without preconceived ideas. After two years of daily, intensive, incremental brain and movement exercises, Pedro underwent a complete recovery. After he died (mountain climbing at the age of seventy-two!), Paul had an autopsy performed on Pedro and discovered that 97 percent of the nerves in a key pathway in his brain stem were destroyed. Paul had an epiphany: the exercises that Pedro had done had reorganized and rewired his brain and built new processing areas and connections that worked around the stroke damage. It meant that even the brain of an old man was plastic.

"Paul's research was in vision. One of his first applications of neuroplasticity was to develop a device to help the blind see. 'We see with our brain, not with our eyes,' he said, arguing that the eyes are merely a 'data port'; its receptor, the retina, converts information from the electromagnetic spectrum that surrounds us -- in this case, light -- into electrical discharge patterns, which are sent down the nerves. There are no images or pictures in the brain (just as there are no sounds, smells, or tastes), just patterns of electrical-chemical signals. Based on a comparative analysis of the retina and the skin, Paul determined that the skin, too, could detect images, as it does, for instance, when we teach a child the letter A by tracing it on his skin. The skin's touch receptors convert that information into electrical discharge patterns, which are then sent to the brain.

"So Paul developed a device consisting of a camera, which sent pictures to a computer, which converted them to pixels (little dots like those that make up the picture on a computer screen), and sent that information to a small plate of electrodes that fits on the tongue -- the prototype of the device Ron Husmann used. He called it the 'tactile-vision device.' Each electrode functioned like a pixel. When the subject aimed the camera at an image, some of the electrodes would fire tiny pulses of controlled electrical stimulation to represent light and slightly fewer to represent gray, while some remained off, to represent darkness. The same image that appeared before the camera appeared on the subject's tongue. Paul and the team decided to use the tongue as the 'data port' because it has no layer of dead skin and is moist, so it is a great conductor. And it has so many nerves that Paul thought it would deliver a high-resolution image to the brain.

"Subjects who had been blind since birth and used the device were able, with some training, to detect moving and looming objects; they could differentiate the faces of 'Betty' and 'Twiggy,' and they could 'see' complex images, such as a vase in front of a telephone. A blind man was able to use the tactile-vision device to detect perspective and even sink a basketball, Paul called this process 'sensory substitution.' It was a brilliant example of brain plasticity, because circuits in the brain that processed touch reconfigured themselves to connect to the brain's visual cortex.

"But the tactile-vision device was doing more than providing a new way to help a blind person see. It showed that, in principle, the brain could be rewired by a sensory experience. The senses provided direct avenues to rewire the brain."



Norman Doidge


The Brain's Way of Healing: Remarkable Discoveries and Recoveries from the Frontiers of Neuroplasticity


Penguin Group


Copyright 2015 by Norman Doidge


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