In breakthrough that may aid blind, Israeli scientists find mice use whiskers to ‘hear’
Weizmann Institute researchers use AI models to show the act of ‘whisking’ allows mice to generate sounds that, encoded in their brain’s auditory cortex, aid them in navigation
Reporter at The Times of Israel
Navigating through the night, mice move their whiskers, brushing them against objects to detect and identify them.
For the past few decades, scientists viewed this behavior, known as whisking, as purely an act of touch.
But researchers at the Weizmann Institute of Science have discovered that subtle sounds are produced by the movements of a mouse’s whiskers. These sounds are then picked up by the mouse’s ears and processed in its auditory cortex. Mice can use these sounds to enhance their sense of touch and improve their perception of the environment around them.
“Mouse whiskers are so delicate that no one had thought of checking whether they produce sounds that mice can hear,” said Prof. Ilan Lampl of Weizmann’s Brain Sciences Department, who led the study with lead researcher Dr. Ben Efron, then a PhD student, Dr. Athanasios Ntelezos and Dr. Yonatan Katz, all from Weizmann.
“We searched a lot, but not a single paper mentioned this possibility,” Lampl said.
Their findings, published recently in Current Biology, offer a unique glimpse into the complexity of natural perception, which commonly involves input from multiple senses – in this case, touch and hearing.
The scientists said the principles of their study could be applied to help visually impaired individuals distinguish between distinct sounds or design robotics to create early warning sensors in limited visibility conditions.
A combination of senses
In a teleconference call, Lampl, Efron, and Ntelezos talked about their study.
They had been working on the mouse’s sensory system and investigating different aspects of the cortex, the outermost layer of the brain that processes functions such as thinking, emotion, memory, and language.
In their work, the researchers look at the integration of different senses and how the information is shared between them.
In daily life, people often combine two senses without thinking twice, Lampl said. For example, people might shake a plastic bottle to hear how much water is left inside, or listen for the rustle of a chocolate bar wrapper at the bottom of a bag.
“We started thinking about what other sensory systems we could combine,” Efron said.
Sensations in mice might have developed in the course of evolution to help mice hunt for prey or avoid predators.
“One possibility is that they use their whiskers to determine whether seeds are solid or hollow,” Lampl said. “To avoid detection by predators such as owls, they might choose to cross a field of green grass instead of dry straw.”
Mouse uses its whiskers on aluminum foil. This demonstrates that natural whisking produces audible sound (Courtesy/Weizmann Institute of Science)
The researchers used sensitive microphones that can record ultrasonic frequencies, which are beyond the upper limit of the audible range for humans. They placed the microphones some 2 centimeters (three-quarters of an inch) from the source of the sound, about the same distance as the mouse’s whiskers are to its ears.
Mice whiskers are about as thick as human hair at the base, becoming thinner at the tip, which helps them create sounds.
The researchers started out recording the sounds made by whiskers probing different surfaces, including dried bougainvillea leaves and aluminum foil. They said they used the foil because it makes a “distinct” sound.
They placed electrodes inside the mouse brain to record the activity of neurons, wondering if the mouse brain would respond to the sounds.
The researchers were surprised to see that there was significant activation of neurons in the auditory cortex when the mice brushed their whiskers against the objects.
Efron said that this suggested that mice “could really hear” the sounds activated by the whiskers.
However, he said, the scientists needed to make sure that the activation of the neurons was not due to information coming from a tactile sensation of the whiskers.
All the sensory information that mice receive goes through their whisker follicles up to their brain through a single nerve. After this nerve was cut, the mice’s auditory cortex still responded to the sounds.
AI models confirm findings
The researchers developed an artificial intelligence (AI) machine-learning model that was taught to identify objects based on the collective neural activity recorded in the mice’s auditory cortex.
Next, the scientists trained another machine-learning model to identify objects on the basis of sounds made by the mice’s whiskers. These two models confirmed that “it’s really the sound that is driving the neuronal activity,” Efron said.
The study’s results could help the visually impaired who use white canes to navigate their environment.
“White canes give people not only tactile sensation to tell them what type of floor they’re walking on, but the sound provides information about whether it’s concrete or wood,” Lampl said. “The whisking of mice might provide further understanding of our sensory systems.”
The Times of Israel Community.