Evolution and humans: eye ear coordination (Evolution)

by David Turell @, Monday, July 24, 2017, 01:56 (2553 days ago) @ David Turell

Eye movement and ear drum movement are coordinated:


"Jennifer Groh at Duke University in Durham, North Carolina, and her team have been using microphones inserted into people’s ears to study how their eardrums change during saccades – the movement that occurs when we shift visual focus from one place to another. You won’t notice it, but our eyes go through several saccades a second to take in our surroundings.

"Examining 16 people, the team detected changes in ear canal pressure that were probably caused by middle-ear muscles tugging on the eardrum. These pressure changes indicate that when we look left, for example, the drum of our left ear gets pulled further into the ear and that of our right ear pushed out, before they both swing back and forth a few times.

"These changes to the eardrums began as early as 10 milliseconds before the eyes even started to move, and continued for a few tens of milliseconds after the eyes stopped.

"We think that before actual eye movement occurs, the brain sends a signal to the ear to say ‘I have commanded the eyes to move 12 degrees to the right’,” says Groh. The eardrum movements that follow the change in focus may prepare our ears to hear sounds from a particular direction.

"Never before has the position of the eyes been seen to have an effect on the ears, says Dave Bulkin at Cornell University in Ithaca, New York.

"How our moving eardrums affect what we hear is unclear, says Groh. One theory for why the eyes and ears move together in this way is that it helps the brain make sense of what we see and hear.

"The discovery could lead to better hearing aids, which currently amplify all sound equally, regardless of where it is coming from.

"The brain of a person with normal hearing can focus on sound from a person you’re talking to in a restaurant, while ignoring a conversation at a nearby table, says Groh. “I could imagine a mechanism being incorporated into hearing aids that picks up signals of eyes moving to a new location and tries to amplify the sound at that location,” she says."

Comment: This is a logical arrangement. I imagine it will be found to be present in many animals.

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