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As your eyes move in the direction of stimulus, your eardrums move in sync with them, according to a new study of humans and monkeys that appears in latest Proceedings of the National Academy of Sciences.

The research could open up new avenues of research into two of our basic senses, according to the researchers from Duke University, University of Southern California and the University of Florida.

“The eardrum movements literally contain information about what the eyes are doing,” said Jennifer Groh, lead author, Duke professor of psychology and neuroscience. “This demonstrates that these two sensory pathways are coupled, and they are coupled at the earliest points.”

Sixteen people between the ages of 18 and 45 were seated in a dark room. Their ears were outfitted with Tucker Davis Technologies microphones, which are sensitive enough to pick up the minute vibrations in the middle ear and cochlear hairs, called optoacoustic emissions, which are triggered by the brain to manipulate the eardrum.

LED lights were displayed to the participants, who were not allowed to move their heads. The eye movements were tracked with an infrared camera, and precisely matched against the microphone readings.

The same experiments were done on three monkeys.

Half of all the trials were done in complete silence. The other half were done with unrelated clicking sounds played in the room.

The results showed that, despite the sound interference, when the eyes moved, the ears moved in concert, they conclude.

“We demonstrated a regular and predictable pattern of oscillatory movements of the eardrum associated with movements of the eyes,” they write. “When the eyes move left, both eardrums initially move right and then oscillate for three to four cycles, with another one to two cycles occurring after the eye movement is complete. Eyes movements in the opposite direction produce an oscillatory pattern in the opposite direction.”

The newly-discovered linkage could prove to further our understanding of how healthy, and unhealthy, coordination of sensory information, said David Murphy a Duke doctoral student who was co-first author.

“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,” said Murphy. “It could also signify a marker of a health interaction between the auditory and visual systems.”

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