Mice actually listen to their whiskers touching things

Inside dark, hidden burrows, mice rely on their whiskers to make sense of the world. For decades, scientists believed that whisking – the brushing of whiskers against surfaces – was purely a tactile process.

But researchers at the Weizmann Institute of Science have uncovered a surprising twist. Whisking doesn’t just involve touch. It generates sound.

Published in the journal Current Biology, the study shows that these tiny sounds activate the auditory cortex in mice, revealing a previously unnoticed sensory connection.

The implications stretch far beyond mice. They hint at how brains might merge different senses to create a fuller picture of the surroundings.

Mice whiskers make sounds

“Whiskers are so delicate that no one had thought of checking whether they produce sounds that mice are able to hear,” said Professor Ilan Lampl of Weizmann’s Brain Sciences Department.

Lampl’s team started by recording the sounds whiskers make when they brush against different surfaces. They used sensitive microphones capable of picking up ultrasonic frequencies – sounds beyond human hearing. The setup mimicked the distance between a mouse’s whiskers and ears.

Surprisingly, the microphones caught faint yet distinct sounds. Whiskers brushing against Bougainvillea leaves and aluminum foil each produced unique acoustic signatures.

These whisker-generated sounds weren’t loud, but they were consistent enough for the researchers to wonder: Are mice actually listening to their own whiskers?

Mice brains listen to whisker sounds

To answer that question, the researchers recorded neural activity in the auditory cortex of mice. They wanted to see if the brain responded to these whisker-generated sounds.

The results stunned them. The auditory cortex lit up every time a mouse whisked against a surface, even when the researchers blocked the pathways that convey touch. The brain wasn’t just feeling the whisker’s touch. It was listening to it.

Why listen to their own whiskers?

Mice navigate through dense, cluttered environments. They sniff, feel, and now, it seems, they also listen. This auditory feedback might help them distinguish between surfaces.

The sound of whiskers brushing against a dry leaf may signal danger. The rustle of aluminum foil might mean food. Lampl suggests that mice may have developed this sensory connection to avoid predators.

“Since whisking generates much weaker sounds than walking, a mouse could rely on it when, for example, choosing whether to walk across a brittle, drier field of crops versus a fresher, quieter one, to avoid being detected by an owl,” said Lampl.

AI confirms that mice identify sounds

To confirm that these sounds mattered to the mice, the researchers brought in artificial intelligence (AI). They trained two machine-learning models.

One model analyzed the neural activity in response to whisker-generated sounds. The other analyzed the recorded sounds themselves. Both models accurately identified objects based solely on sound patterns.

The takeaway? The mice’s brains were not just picking up sound. They were interpreting it.

Mice trained to hear whisker sounds

With AI results in hand, the researchers designed a behavioral test. They trained mice whose touch sensation had been blocked to recognize aluminum foil based solely on its whisker-generated sound.

The mice caught on quickly. When they heard the sound of whiskers scraping foil, they responded as if they were touching it.

This finding confirmed that the auditory cortex could interpret whisker sounds as sensory information, even without tactile input.

Listening to whiskers helps mice survive

Why would mice evolve to listen to their own whiskers? Lampl believes it’s all about survival.

The sound of whiskers brushing against objects is subtle – much quieter than a mouse’s footsteps. This quiet feedback allows a mouse to navigate without attracting predators.

“Whisking could also help a mouse figure out whether a stem is hollow or sufficiently juicy and worthy of a bite,” Lampl explained.

The ability to detect subtle acoustic differences might help mice decide what to bite, what to avoid, and where to hide.

Mouse whisker insights for robots

The study’s findings have broader implications. If mice can merge sound and touch to perceive their environment, robots might do the same.

Dr. Ben Efron, a lead researcher in the study, sees potential in collision-avoidance sensors that rely on sound.

“Integrating different types of sensory input is a major challenge in the design of robotic systems. The mouse brain’s whisking system might provide inspiration for technologies that would address this challenge,” said Dr. Efron.

In smoke-filled rooms, underwater environments, or other low-visibility conditions, sensors that interpret subtle sounds could prevent collisions. The mouse brain, it seems, may offer a blueprint for such systems.

How blind people could benefit

The study also opens doors for sensory rehabilitation. For people with sensory impairments, integrating touch and sound could enhance perception.

Consider how blind individuals use the sound of a white cane tapping against a surface. Mice, it turns out, might be doing something similar with their whiskers.

If researchers can replicate this multisensory integration in prosthetic devices, they could create more intuitive feedback systems. Imagine a prosthetic hand that not only feels an object but also “hears” its texture through vibrations.

Tiny whiskers, big sensory impact

Mice whiskers are as thick as human hair at the base, ranging from 40 to 80 microns.

As they extend outward, they become much thinner, ending at just 3 to 4 microns at the tip. This thin, sensitive structure helps them create tiny sounds and detect slight vibrations.

This study is just the beginning. If mice can use whisker-generated sounds to identify objects, what other animals might do the same? Could cats or rats also listen to their whiskers?

The researchers plan to explore how different animals might use touch-generated sounds. They also want to see if mice can learn to distinguish between even more complex sounds or if they can adapt to new auditory cues.

Significance of mice whisker sounds

What started as a simple investigation into whiskers has revealed a complex sensory connection. Mice don’t just feel with their whiskers – they listen to them.

The implications stretch beyond the burrow, hinting at new ways to merge sound and touch in both nature and technology.

And for researchers like Lampl, the work is far from over. The brain’s ability to integrate multiple senses opens up a world of possibilities, from robotic sensors to prosthetic feedback systems. The whispers of whiskers might just be the start.

The study is published in the journal Current Biology.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–