The brain is a supercomputer that controls multiple functions at the same time. Thinking, talking, feeling, seeing, hearing, remembering, and walking are all controlled by the brain. A new study is examining how the brain coordinates what we see and what we hear. More specifically, when the eyes move, so do the eardrums. The investigators from Duke University feel that their research may provide new insights into understanding hearing disorders.
The eyes and ears work in combination to help us understand the sights and sounds around us. The research study team members sought to know where and how the brain combines the two types of information. Although the brain matches up vision and hearing based on where the stimuli are coming from, the visual and auditory systems locate the stimuli in different ways. The visual system provides a snapshot of a visual scene, and the auditory system calculates where sounds are coming from based on timing and loudness.
The study utilized both humans and rhesus monkeys. In the experiment, 16 participants were instructed to sit in a dark room and observe shifting LED lights with their eyes. The study members were wearing small microphones within their ear canals to pick up slight vibrations that occurred when the eardrum swayed back and forth.
The eardrums vibrate in response to outside sounds. The brain also controls eardrum movements via the small bones in the middle ear and the hair cells in the cochlea. It is these actions that control the volume of sounds that reach the inner ear and the brain. The researchers note that when the eyes move, both eardrums move in sync with each other. This vibration of the eardrums continues until after the eyes have stopped moving. It is possible that this indicates an interaction between the auditory and visual systems.
The researchers believe that the movements demonstrate a healthy relationship between the auditory and visual systems. The findings indicate that when the eyes move, both eardrums move in sync with each other. One side bulging inward and at the same time, the other bulging outward. This movement continues until the eyes stop moving. Any eye movements in the opposite direction cause different patterns of vibrations. Large eye movements cause more significant fluctuations than the ones associated with the smaller eye movements. The team feels that the eardrums are encoding spatial information about eye movements, which could help the brain merge visual and auditory space.
The research team continues to investigate how the vibrations of the eardrum affect what we hear. They are also curious as to what part this may play in hearing disorders. In the future, the researchers hope to determine if up and down eye movements may cause unique eardrum vibrations. For now, this study provides new insight into how the brain synchronizes what a person sees and what they hear. It may lead to a better understanding of hearing disorders.