Bats that use echolocation as they fly through the dark have special genes that protect their cochlear hair cells so they don’t go deaf to their own ultrasonic screeching.
Echolocation occurs when an animal emits a sound that bounces off objects in the environment, and returns echoes that provide information about the surrounding space – how far away an object is, its size, shape and density, and the direction it can move .
Most, but not all, bats use echolocation to navigate in the dark and find food sources, with some emitting sounds of up to 140 decibels, which is equivalent to a jet engine taking off.
Prolonged exposure to anything above 80 decibels can cause ear damage in most mammals, according to new scientist.
Above 120 decibels can be painful and cause permanent damage to the fine hairs in the inner ear, or cochlea, that help with hearing.
Researchers in China found that bats that use echolocation overexpress genes that protect cochlear hair cells. That could ultimately help people with noise-induced hearing loss
So why don’t bats go deaf to their own high-frequency squeaks?
While humans can generally detect sounds in a frequency range of about 20 Hz to 20 kHz, bat calls range from as low as 11 kHz to as high as 212 kHz.
Echo locating bats have a muscle in their ears that muffles incoming sounds, New Scientist reports, but that isn’t enough to prevent hearing loss from their nocturnal roars.
Peng Shi, a biomedical engineer at the Institute of Zoology of the Chinese Academy of Sciences in Kunming, attached electrodes to the heads of five species of echolocating bats, as well as non-echolocating fruit bats and laboratory mice.
Most, but not all, bats use echolocation to locate food sources in the dark, with some emitting sounds of up to 140 decibels – equivalent to a jet engine taking off
The animals were exposed for two hours to sounds within their hearing range of 120 decibels, which is equivalent to the tearing of a chainsaw.
The experiment was repeated on the mammals a week later.
While the mice and fruit bats showed signs of hearing loss and had lost a significant amount of cochlea hair cells, the echolocating bats were unaffected.
By conducting genetic testing, the team found that in all five species of echolocating bats, “different genes that protect cochlear hair cells from intense sounds were overexpressed,” the researchers reported.
The researchers believe that understanding how the overexpression of the ISL1 gene “significantly improved cochlear hair cell survival” could ultimately help people with noise-induced hearing loss.
In particular, the overexpression of the ISL1 gene ‘significantly improved the survival of cochlear hair cells’.
While that doesn’t mean much for people with congenital hearing problems, the researchers said it could eventually be used to develop methods to prevent or improve noise-induced hearing loss.
Studying echolocation may have another benefit for people with disabilities: A study published in June found that blind people can learn a form of echolocation in just 10 weeks by clicking their tongue.
Durham University researchers said patients with vision loss can receive echolocation training to improve their mobility and independence.
Clicking sounds are created by sharply pulling the center or front of the tongue away from the roof of the mouth once or twice per second. Echoes of the sound are then used to interpret a person’s environment.
A click of the tongue: Cholocation works by creating sound waves. These bounce off objects and return an echo, allowing echolocators to create a three-dimensional ‘image’ in their mind
What is echolocation?
Echolocation is the use of sound waves and echoes to determine where objects are in space.
Bats use it to navigate in the dark and find food.
To do this, they send sound waves from their mouth or nose.
When the sound waves hit an object, they produce echoes.
These echoes bounce off the objects and return to the bat’s ears.
Bats use these echoes to determine where the object is, its size and shape.
Bats are not blind, but use echolocation to quickly find their way at night.
Source: Arizona State University School of Life Sciences
The echo activates the visual processing area in the brain and enables expert echolocators to create three-dimensional “images” in their minds.
During the training program, a team led by psychologist Lore Thaler worked with 12 blind and 14 sighted participants, ages 21 to 79, in 20 training sessions lasting two to three hours.
The blind participants also took part in a three-month follow-up study to assess the effects of the training on their daily lives.
According to a report in the magazine PLOS One, Thaler and his colleagues found that both sighted and blind people could learn the technique and in some cases compared it to expert echolocators at the end of the training.
The study also found that neither age nor visual skills were a factor in echolocation learning or the ability to apply the skill to new tasks.
In the follow-up survey, all blind participants reported improved mobility and 83 percent reported improved independence and well-being.
Researchers say the results generally suggest that the ability to learn click-based echolocation is not greatly limited by age or eyesight.
This has positive implications for the rehabilitation of people with vision loss or in the early stages of progressive vision loss, they say.
“I can’t think of any other work with blind participants that has received such enthusiastic feedback,” Thaler said in a statement.
“We are very excited about this and think it would be useful to provide information and training in click-based echolocation to people who may still have good functional vision, but are expected to have visual impairment later in life.” will lose because of progressive degenerative eye disease. .’