Summary: A new study in PNAS shows that eye movements and eardrum motion are linked, revealing an early-stage interaction between vision and hearing.
New evidence shows that simply moving the eyes causes the eardrums to move as well.
Researchers at Duke University report that when people shift their gaze while keeping their head still, the eardrums vibrate in a predictable pattern—even when no external sound is present. These tiny vibrations begin just before or at the moment the eyes move, suggesting coordinated motor commands in the brain simultaneously influence both the eyes and the ears.
“It’s as if the brain signals, ‘I’m about to move the eyes, so I’ll tell the eardrums too,’” said Jennifer Groh, professor of psychology and neuroscience at Duke. The finding offers a new perspective on how the brain integrates what we see and what we hear, and it could shed light on certain hearing challenges such as difficulty following a conversation in noisy environments.
The study, conducted in both human volunteers and rhesus monkeys, appears in the journal Proceedings of the National Academy of Sciences. It builds on the long-standing idea that vision and audition interact closely: people comprehend speech more easily when they can see a speaker’s face, and audiovisual illusions like the McGurk effect demonstrate how visual lip movements can change auditory perception. What remained unclear was how and where in the sensory pathways the two systems first converge.
Groh explains the challenge: the visual system and the auditory system determine spatial location very differently. Visual information provides a snapshot of the scene tied to eye position, while the auditory system computes sound location from timing and loudness differences between the two ears. Because our eyes constantly move, the brain must reconcile shifting visual input with relatively stable auditory cues—finding a common reference for visual and auditory space.
To explore this, doctoral student Kurtis Gruters and colleagues asked 16 participants to sit in a dark room and follow LEDs that shifted position, making saccadic eye movements while keeping their heads still. Each participant wore small microphones in the ear canals sensitive enough to detect slight eardrum motions. Measurements showed that when the eyes moved, both eardrums oscillated together: one eardrum bulged inward while the other bulged outward and then reversed, continuing through the movement and for a short period afterward. Eye movements in opposite directions produced correspondingly reversed eardrum motion patterns, and larger saccades produced larger eardrum oscillations.
These eye movement-related eardrum oscillations, abbreviated EMREOs by the researchers, began as early as 10 milliseconds before saccade onset in humans and at saccade onset in monkeys. Importantly, the oscillations occurred in silence—no external sound was required—and their amplitude and phase encoded the direction and horizontal magnitude of the saccade. The bilateral, coordinated nature of the motion suggests the brain generates binaural cues tied to eye position that could help align auditory and visual spatial information.
David Murphy, a doctoral student in Groh’s lab and a co-first author on the paper, noted that “the fact that these eardrum movements encode spatial information about eye movements means they could help the brain merge visual and auditory space. They may also serve as a marker of healthy interaction between the auditory and visual systems.”
The research team included collaborators from the University of Southern California and the University of Florida. Ongoing work will examine whether vertical eye movements produce distinct EMREO signatures and how these eardrum motions affect auditory perception. Understanding this coupling at early sensory stages may also inform research into hearing disorders and difficulties with auditory scene analysis—like focusing on one voice in a noisy room.
About this research
Source: Kara Manke, Duke University
Publisher: NeuroscienceNews.com
Image credit: Jessi Cruger and David Murphy, Duke University
Original research: Proceedings of the National Academy of Sciences (PNAS). DOI: 10.1073/pnas.1717948115
Abstract (summarized)
Interactions between sensory pathways, such as vision and audition, are known to occur in the brain but the earliest site of integration has been unclear. Using ear-canal microphone recordings from humans (19 ears in 16 subjects) and monkeys (5 ears in three subjects) performing saccadic eye movements to visual targets, the investigators observed that the eardrum moves in conjunction with eye movements. These eye movement-related eardrum oscillations are oscillatory, begin just before or at saccade onset, and occur without external sound. The amplitude and phase of these oscillations depend on saccade direction and horizontal amplitude, persisting through the saccade and into subsequent fixation. The authors discuss the possibility that such mechanisms create eye movement-related binaural cues that aid the brain in assessing the spatial correspondence between visual and auditory stimuli as the eyes move.