Human echolocation

Echo-related activity in the brain of an early-blind, trained echolocator is shown on the left. There is no activity evident in the brain of a sighted person not so trained (shown on the right) listening to the same echoes

Some blind people are skilled at echolocating silent objects simply by producing mouth clicks and listening to the returning echoes. Although few studies have been performed on the neural basis of human echolocation, those studies report activation of primary visual cortex during echolocation in blind expert echolocators.[1][13][14] The driving mechanism of this brain region remapping phenomenon is known as neuroplasticity.

In a 2014 study by Thaler and colleagues,[15] the researchers first made recordings of the clicks and their very faint echoes using tiny microphones placed in the ears of the blind echolocators as they stood outside and tried to identify different objects such as a car, a flag pole, and a tree. The researchers then played the recorded sounds back to the echolocators while their brain activity was being measured using functional magnetic resonance imaging. Remarkably, when the echolocation recordings were played back to the blind experts, not only did they perceive the objects based on the echoes, but they also showed activity in those areas of their brain that normally process visual information in sighted people, primarily the primary visual cortex or V1. This result is surprising, as visual areas are normally only active during visual tasks. The brain areas that process auditory information were no more activated by sound recordings of outdoor scenes containing echoes than they were by sound recordings of outdoor scenes with the echoes removed. Importantly, when the same experiment was carried out with sighted people who did not echolocate, these individuals could not perceive the objects and there was no echo-related activity anywhere in the brain. This suggests that the cortex of blind echolocators is plastic and reorganizes such that primary visual cortex, rather than any auditory area, becomes involved in the computation of echolocation tasks.

Despite this evidence, the extent to which activation in the visual cortex in blind echolocators contributes to echolocation abilities is unclear.[9] As previously mentioned, sighted individuals have the ability to echolocate; however, they do not show comparable activation in visual cortex. This would suggest that sighted individuals use areas beyond visual cortex for echolocation.

Echolocation has been further developed by Daniel Kish, who works with the blind through the non-profit organization World Access for the Blind.[16] He leads blind teenagers hiking and mountain-biking through the wilderness, and teaches them how to navigate new locations safely, with a technique that he calls "FlashSonar".[17] Kish had his eyes removed at the age of 13 months due to retinal cancer. He learned to make palatal clicks with his tongue when he was still a child, and now trains other blind people in the use of echolocation and in what he calls "Perceptual Mobility".[18] Though at first resistant to using a cane for mobility, seeing it as a "handicapped" device, and considering himself "not handicapped at all", Kish developed a technique using his white cane combined with echolocation to further expand his mobility.[18]

Kish reports that "The sense of imagery is very rich for an experienced user. One can get a sense of beauty or starkness or whatever—from sound as well as echo."[17] He is able to distinguish a metal fence from a wooden one by the information returned by the echoes on the arrangement of the fence structures; in extremely quiet conditions, he can also hear the warmer and duller quality of the echoes from wood compared to metal.[17]

Thomas Tajo was born in the remote Himalayan village of Chayang Tajo in the state of Arunachal Pradesh in the north-east India. He became blind around the age of 7 or 8 due to optic nerve atrophy and taught himself to echolocate. Today he lives in Belgium and works with Visioneers or World Access to impart independent navigational skills to blind individuals across the world. Tajo is also an independent researcher. He researches the cultural and biological evolutionary history of the senses and presents his findings to scientific conferences around the world.[19]

Ben Underwood

Ben Underwood was a blind American who was born on January 26, 1992, in Riverside, California. He was diagnosed with retinal cancer at the age of two, and had his eyes removed at the age of three.[20]

He taught himself echolocation at the age of five, becoming able to detect the location of objects by making frequent clicking noises with his tongue. This case was explained in 20/20: Medical Mysteries.[21] He used it to accomplish such feats as running, playing basketball, riding a bicycle, rollerblading, playing football, and skateboarding.[22][23] Underwood's childhood eye doctor claimed that Underwood was one of the most proficient human echolocators.

He inspired other blind people to follow his leads. He passed away in 2009 due to cancer.

Lawrence Scadden lost his sight as a child due to illness, but learned to use echolocation well enough to ride a bicycle in traffic. (His parents thought that he still had some sight remaining.)[24] In 1998, he was interviewed at the Auditory Neuroethology Laboratory at the University of Maryland about his experience with echolocation.[7] The researchers were aware of the Wiederorientierung phenomenon described by Griffin[6] where bats, despite continuing to emit echolocation calls, use path integration in familiar acoustic space. Scadden said he did the same, as echolocation required extra effort.

The National Science Teachers Association created the "Lawrence A. Scadden Outstanding Teacher Award of the Year for Students With Disabilities" in his honor.[25]

Lucas Murray, from Poole, Dorset, was born blind, and is one of the first British people to have learned human echolocation, having learned it from Daniel Kish.[26] Lucas' parents saw a documentary about Daniel Kish teaching Ben Underwood echolocation.[27][28] Months later, they learned that Daniel would be visiting a Scottish charity called Visibility[29] and contacted him. Kish taught the five-year-old Lucas the basics of echolocation over four days. By age seven, Lucas was proficient enough to not only accurately tell the distance of objects, but also their material, and could play with other children in sports such as rock climbing and basketball.[30][31] In 2019, he enjoyed a week's work experience with South Western Railway.[32]

The scientist Kevin Warwick experimented with feeding ultrasonic pulses into the brain (via electrical stimulation from a neural implant) as an additional sensory input. In tests he was able to discern distance to objects accurately and to detect small movements of those objects.[33]

Blind from birth, Juan Ruiz lives in Los Angeles, California. He appeared in the first episode of Stan Lee's Superhumans, titled "Electro Man". The episode showed him capable of riding a bicycle, avoiding parked cars and other obstacles, and identifying nearby objects. He entered and exited a cave, where he determined its length and other features.