S u m m a r y :
When you move your eyes, your eardrums are moved too! A new study describes how both senses work together to process the sights and sounds in one’s environment. The findings are published in the Proceedings of the National Academy of Sciences.
The Senses Awaken
Your eyes and ears are in greater synchrony than one would have thought. We all know that the eyes and ears work in concert to interpret sights and sounds, but the new information introduced in this study shows that this relationship has more ‘history’ than initially thought. The research, conducted by investigators from Duke University, entails the discovery of how the simple act of moving one’s eyes will cause the eardrums to move too; for instance, if you move your eyes from one side to another while your head is kept still, your eardrums will be simultaneously experiencing vibrations, even if no sound occurs. Both senses, then, interpret information from one’s surroundings, and the one pulling their strings is the brain, explain the authors.
It is to be noted that the findings were replicated in humans, thereby providing reliable information as to the brain coordination behind our sight and hearing; the results are also hoped to provide new insight into hearing disorders.
Brain Decides to Talk to Both Senses
Another interesting finding is that the eardrum vibrations happen a little before the eye movements, suggesting that the motions in both organs are monitored by the same motor neurones in the brain; the latter would be calling both the eyes and ears to move, so to say.
“It’s like the brain is saying, ‘I’m going to move the eyes, I better tell the eardrums, too,’” says study author Jennifer Groh.
Hearing With the Eyes
Normally, humans connect the use of both senses to communicate: they will understand each other better when they look at the person talking to them while also watching the movement of their lips. What remains much of a puzzle, though, is the how behind the combination of the two different forms of sensory stimuli.
“Our brains would like to match up what we see and what we hear according to where these stimuli are coming from, but the visual system and the auditory system figure out where stimuli are located in two completely different ways,” said Groh. “The eyes are giving you a camera-like snapshot of the visual scene, whereas for sounds, you have to calculate where they are coming from based on differences in timing and loudness across the two ears.”
“You Move, I move”
According to Groh, the two forms of sensory data are in constant flux with one another because of the incessant movement of the eyes within the head.
The team found that during eye movements, the two eardrums would move in synchrony with one another, such that one side would be vibrating inwards while the other would do the same outwards. This back-and-forth vibration would continue even after the eyes had stopped moving. Also, the eyes moving in opposite directions causes opposite vibration sequences.
Same Intensity of Movements
Yet another discovery was that larger eye movements were accompanied by bigger vibrations as opposed to smaller eye movements.
“The fact that these eardrum movements are encoding spatial information about eye movements means that they may be useful for helping our brains merge visual and auditory space,” says co-author David Murphy. “It could also signify a marker of a healthy interaction between the auditory and visual systems.”
Now, what does this mean for us? Question yet to be answered. The team is currently working to find out how the eardrum vibrations actually affect our hearing. They believe that this phenomenon might be playing a role in hearing disorders.
“The eardrum movements literally contain information about what the eyes are doing,” Groh said. “This demonstrates that these two sensory pathways are coupled, and they are coupled at the earliest points.”