A New Portal to the Brain
“Blind since birth, Marie-Laure Martin had always thought that candle flames were big balls of fire. The 39-year-old woman couldn’t see the flames themselves, but she could sense the candle’s aura of heat. Last October, she saw a candle flame for the first time. She was stunned by how small it actually was and how it danced. There’s a second marvel here: She saw it all with her tongue.”
In fact, sight became possible for Marie-Laure largely because of the creativity, hard work, and persistence of Dr. Bach-y-rita, a neuroscientist at the University of Wisconsin-Madison, who died in 2006. Dr. Bach-y-rita, a friend of my father’s, was one of those scientists we talk about in class who constantly questions the evidence and seeks new interpretations and observations to difficult problems through science. His early work focused on demonstrating how patients could recover following a stroke. For example, in the 1970s when TV ping pong games first came out, he developed some computer adaptations and applied them to the rehabilitation of patients after stroke. He was able to demonstrate that when patients got captured by the game, they forced their arms to work (without realizing how hard they were working), and their mobility improved.
Simply the use of rehabilitation in his work demonstrates his creativity for there was a time when the notion of a critical period was applied to almost all behaviors. When asked if it was possible for a person who had been blind for his entire life to “learn to see” as an adult, most people generally assumed that it was not possible. Among those who would have claimed it impossible for an adult to regain vision would have been Hubel and Weisel (1970) who demonstrated that a kitten whose eyelid was sewed shut after birth remained permanently blind in that eye after the stitches were removed. However, two years later, other scientists performed the same experiment and showed that if you worked to rehabilitate the cat’s vision after the stitches were removed, the cat would recover vision – indicating the absence of a “critical period.” Few people paid any attention to that study, however, because it didn’t fit with the commonly accepted worldview at that time. In fact, according to Bach-y-rita, the neurosciences are particularly slow to shift paradigms. As a result, it took a really long time for people to accept the fact that the brain was not hardwired and that damage to the brain was not necessarily permanent – even though published studies as early as 1915 in the Journal of the American Medical Association indicated this to be a strong possibility!
As Bach-y-rita pointed out, it just doesn’t make sense to use the analogy of a computer to describe the functioning of the human brain. He uses the term ‘volume transmission’ and provides an example of a college classroom to make the point that our brains care too much about saving time and energy to accept such a stagnant explanation. Imagine students leaving a classroom, wandering into the halls, meeting with friends, making decisions to go one place or another, and eventually ending up where they are supposed to be. This patterning is far too complex to be explained through action potentials. In fact, he argued, if you calculated how much energy it would take for all of the action potentials necessary to do all of the things that we do, it is clear that there would never be enough room in our heads for our brains to exist.
It was these types of thoughts that led Bach-y-rita and others toward the understanding of the brain as extremely malleable. Through rehabilitation studies, meditation studies, and MRI analysis, the concept of neuroplasticity is now widely accepted. Studies conducted over the past 40 years confirm that the brain is capable of reorganizing itself after injury. In fact, not only is neuroplasticity accepted, the concept of the brain as dynamic, shifting, and capable of change has become a new starting block for many creative and influential scientific studies not just within the field of neurobiology but also within ophthalmology, engineering, and psychology. The concept of neuroplasticity has become an important tool within the scientific community. Therefore, it shouldn’t come as a surprise that our brain, given the necessary tools, can adapt to the loss of vision and recreate that sense through another bodily structure. Our brain is an extremely powerful tool that is fully capable of cross modal plasticity.
Where I started this paper was with the concept of “sensory substitution,” the area in which Dr. Bach-y-rita was most famous. As mentioned by Jessica Wurtz, in her paper last year for this class, the truth is that “we don’t actually see with our eyes. We see with our brain.” And as demonstrated by Dr. Bach-y-rita, the eyes are not the only structure that can provide the sense of vision. He began his work from the premise that if the brain is malleable, then it is trainable. So if humans lack certain abilities (such as vision), then it might be possible – with the use of special tools – to restore those abilities by remolding their brain’s neuronal arrangements. We can help blind people learn to reinterpret visual signals.
Using sensory substitution the “impossible” has now become possible. Due to the brain’s neuroplasticity, new sensory systems can be set up which train the brain to be able to see. Coated in saliva, the tongue can become an electrical conductor. With a camera connected to a control box and the control box connected to a thin sheet of interconnected wires resting on the tongue, the electronic stimulation produced by the wires can allow the brain to receive visual sensory signals. Although a blind person doesn’t have all of the optic neurons that seeing people have, optical images can be picked up by a camera and transmitted through vestibular stimulation to the tongue and with experience and training, those people can learn to see. The tongue can act as a portal to convey somatosensory information to the visual cortex. These studies on heightened sensory awareness and the tactile tongue sensor shed light not only on the plasticity of the brain, but also on the ways in which our brains and neurons are capable of adapting and rearranging in order to correctly interpret signals.
Bach-y-rita’s tactile-sensory substitution work began in 1963. For many years, it was extremely frustrating work. People “laughed in disdain” (his words) at his ideas and even at his published results. In fact, it was only in the last 10 years that his ideas were actually accepted and he was able to consistently get national grants to support his work. It saddens me to think about the loss of such a creative individual. We are left with his thoughts, summarized in 2004, after he learned that he had Stage 4 lung cancer. In this article, Bach-y-rita took the time to think back on his life and the challenges in his work. He proposed that what he would like to have happen in the future was a new field of Theoretical Neuroscience – a place where new concepts could be more readily received. After reading his articles and remembering him as a person, one of Paul Bach-y-rita’s strongest messages was that it is important to always rethink our assumptions. Perhaps ending with his own words is the best way to summarize his life’s work:
“I wondered how much we scientists have ignored in our quest to understand how the brain really works, due to our efforts to be “scientific”.
Bach-Y-Rita, Paul. "Emerging Concepts of Brain Function." Journal of Integrative Neuroscience 4 (2005): 183-205. 20 Feb. 2008.
University Of Wisconsin-Madison. "Paul Bach-Y-Rita, Professor, in Memoriam." The Biomedical Engineering Dept. Newsletter 30 July 2007. 20 Feb. 2008 <http://www.engr.wisc.edu/bme/newsletter/in_memoriam.html>.
Wurtz, Jessica. “Seeing Without Sight”. Neurobiology and Behavior. 20Feb. 2008.