Eyesight & Hearing

Did You Know that Eardrums Move When Your Eyes Move?

You could call it a fun fact about the body and the ways in which we detect sound. Did you know that your eardrums move when your eyes move? A study1 conducted at Duke University found that when the eye focused on moving targets, the eardrum moved as well. Scientists have long known that the inner ear moves with the eyes. However, this study revealed that the eardrum (the middle ear) moves, as well.

The authors of the study believe that there may be a motor command that is generated somewhere to begin the eye movement, which then kicks the middle-ear muscles into action. In other words, the eyes initiate a process that regulates the initial stage of hearing. According to the study, when the eardrum moves according to eye movements, it may help the brain to “connect sights and sounds despite changes in the spatial relationship between the eyes and the ears.”

An easy way to understand this is to think about what happens when your eyes assist hearing by reading lips. Whether a person has hearing loss or is standing in a noisy room, the ability to see a person’s lips when speaking helps to aid hearing. When this happens, your brain is linking visual and auditory signals to make sense of speech. Somehow your brain captures information about movements the eyes are making and incorporates it as it processes information from the eyes and the ears. This is exactly what scientists were trying to decode and understand in this study. As one author put it, “It’s like the brain is saying, I’m going to move the eyes, I better tell the eardrums, too.,” said Jennifer Groh, a professor of psychology and neuroscience at Duke.

Here’s how they conducted the study: Sixteen people sat in a dark room and were asked to follow, with their eyes, LED lights that shifted around the room. They each wore small microphones in their ears. The microphones were highly sensitive and could detect minute vibrations created by movements of the eardrums. Eardrums vibrate when hit by sounds outside the ears, but the brain can make them vibrate, as well. The study found that when the eyes moved to follow the lights, the eardrums moved in sync with one another. They vibrated as long as the eyes were removing.

The So-What Question: Why Is It Important to Know that Your Eyes and Eardrums Are Synced?
One fascinating finding was that when participants kept their head still but moved the eyes from one side to another, they eardrums vibrated, even when there wasn’t any external sound. Researchers say it looks like the brain integrates visual and auditory information to make “the best- informed decision about the world with which it has to interact.”
Scientists are intrigued by these findings and plan to study eye-eardrum interaction more to decode it and understand it more fully.


1: http://www.pnas.org/content/115/6/E1309