Cochlear Implants

In 1978, a surgeon in Melbourne, Australia named Dr. Graeme Clark placed a strange new device inside a patient named Rod Saunders — a set of tiny wires threaded into the inner ear. Saunders had been completely deaf, but after the device was switched on, he could hear sound again, not through his damaged ear parts, but through a device that talked directly to his brain's hearing nerve. Today, more than 700,000 people around the world use a cochlear implant, a piece of technology that is really a brain-computer interface for sound.

By the end of this lesson, you will be able to: • Describe how the ear normally turns sound waves into a signal the brain understands • Explain what part of hearing a cochlear implant replaces, and how • Compare a cochlear implant to a hearing aid • Describe the origin story of the first cochlear implant

Hearing starts when sound waves travel into your outer ear and strike your eardrum, a thin flap of skin that vibrates like a drum. Those vibrations pass through three tiny bones and into the cochlea, a fluid-filled, snail-shaped organ in your inner ear. Inside the cochlea are thousands of microscopic hair cells that bend when the fluid moves, and that bending motion gets converted into an electrical signal. That signal travels along the auditory nerve straight to your brain, which interprets it as sound — a voice, music, a slamming door.

For many people with severe hearing loss, the hair cells in the cochlea are damaged or missing, so no matter how loud a sound is, there's nothing left to turn it into an electrical signal. A cochlear implant solves this by skipping the hair cells completely. It has two main parts: an external piece worn behind the ear with a microphone and a speech processor that turns sound into a digital code, and an internal piece — surgically placed under the skin — with a thin electrode array threaded directly into the cochlea. That electrode array stimulates the auditory nerve directly with tiny electrical pulses, recreating the job the hair cells used to do.

Dr. Graeme Clark grew up watching his father struggle with hearing loss, which pushed him to spend over a decade researching how to safely place electrodes inside the delicate, coiled cochlea without damaging it. His breakthrough came in 1978, when he implanted the first multi-channel cochlear implant — one that could send several different pitches of signal instead of just one — into Rod Saunders in Melbourne. The U.S. Food and Drug Administration approved cochlear implants for adults in 1985 and for children in 1990, and the technology has been improving ever since.