Echolocation and the Blind Boy

Once in a while I come across a story that so blows me away so much that I can’t help but want to share it. This story, about a boy named Ben Underwood, from Elk Grove, California, who lost his sight at the age of 3 to cancer, but was able to accomplish things that will continue to baffle scientists for years to come.

Ben was blind like no other young blind man.   He used clicking noises, called echolocation, to locate objects in his path. With this process he was able to ride his skateboard and bike, do karate, and beat his friends at video games. That’s right, I said video games! How could he do that without seeing the screen?

Ben walked without a seeing-eye dog or cane. By using clicking sounds that he had been doing since he was seven, Ben was able to identify where objects were located in his path and move around them. Did that mean Ben had super-sensitive hearing, and his hears picked up where his eyes left off? Not according to his hearing tests. He hears at the same levels as most of the rest of us. What he does use is the same “radar” system that dolphins and bats use. It’s similar to sonar.

Human echolocation is the ability for people to detect objects in their surroundings by receiving echoes from those objects. By the person actively creating sounds, like clicking or tapping, people who are trained in echolocation can interpret the sound waves reflected by nearby objects, and being able to accurately identify their location and size. Blind people are beginning to use this “acoustic wayfinding” or navigating using sound rather than sight.

There is little information about human echolocation, although there have been quite a few studies of bats and dolphins and their ability to use clicks and sounds to bounce sound waves off objects. Nothing is known about how the brain makes the transitions needed to allow someone to be able to do the same things animals do.

In the first ever study of human echolocation; Canadian researchers used functional magnetic resonance imaging (fMRI) to monitor the brain activity of two blind echolocation experts. Their findings, published today in the open access journal PLoS ONE, show that echolocation puts into motions areas of the brain that normally processes vision.  

Researchers brought in two experts in echolocations for the study. One man (known as EB) was born with a form of cancer that affects cells in the retina (know as retinoblastoma). The other man (LB) lost his vision at 14 following degeneration in the optic nerve — carrying visual information from the eye to the brain. Both men, like Ben, trained themselves to be echolocators. They both use clicks to navigate through town, go hiking and play basketball.

The men were asked to identify objects located in front of them using their clicks. As they made the sounds the researchers recorded them and the fain echoes they produced with high quality stereo equipment. They also took the men outside and asked them to travel around the area and do the same thing. Some of the recordings contained echoes they picked up from trees, cars or lampposts, others did not. Both men were able to determine the shape, size, location and movements of the objects. They also could do the same when the recordings were played back.

The researchers than scanned the brains of the two men, as well as that of two sighted people of the same age as a control. The recordings of the activity activated the auditory cortex, the portion of the brain that processes sounds, in all four participants. They also activated parts of the visual cortex in both of the blind participants — but not in the sighted men. EB, who was more experienced in echolocation, exhibited greater visual cortical activation.

Another difference was found when they compared the brain activity between the outdoor and indoor activities. The recordings containing echoes activated the visual cortex in the blind participants, but not the auditory. Recordings without echoes produced the same pattern of activity as those used in the first experiment.

Researchers are hesitant to form any conclusion due to the limited amount of participants. It would suggest that both men used echolocation in a way similar to vision. They did note that there are numerous studies that show blindness can lead to extensive brain reorganization, and these changes can produce cross-modal activation, activating areas that normally would not process them.

I used the past tense in this story because Ben passed away in 2009, a week before his 17th birthday, from the recurrence of the cancer that blinded him 13 years earlier.   His phenomenal life and attitude has opened up new questions as to the possibilities that there are more avenues to explore when it comes to how the brain is capable of making changes that compensate for disabilities.

One can’t leave this story without giving credit to his extra-ordinary mother, who encouraged him to use his sounds get around. She was not aware, until she tried to enroll him in a school for the blind that her son was unlike other blind children and didn’t fit in with them. He was able to do things other blind people can only dream of, and many sighted people are still in awe of.

This story is not only inspiring, but also shows the potential for future studies of blind echolocators could provide further insights into the underlying mechanisms of the brain.

 

 

 

Sources:

YouTube: The boy who sees without eyes: http://www.youtube.com/watch?v=ikpNZOx5FGk&feature=related

Wikipedia — Human echolocation:

Neurophilosophy — Human echolocation activates visual parts of the brain: http://scienceblogs.com/neurophilosophy/2011/05/human_echolocation_activates_visual_parts_of_the_brain.php

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