Cochlear Implants 1977 – The Bionic Ear

Throughout history, people with hearing impairments have been mistreated or excluded. One of the most prejudiced statements is attributed to Greek scholar Aristotle: 

"All those born deaf become unfeeling and unable to reason."

In humans, sound travels to the cochlea, a spiral-shaped, fluid-filled organ in the inner ear. Microscopic hairs project into the fluid, vibrate in response to sound waves, and convert sounds into nerve impulses that travel along the auditory nerve to the brain. Missing or abnormal hair cells can cause sensorineural hearing impairment resulting from developmental abnormalities, trauma, or disease.

A cochlear implant (CI) is an electronic device that provides a sense of sound to people with hearing impairments. Its external part consists of a microphone, a speech processor that divides sounds into different frequency channels, and a transmitter that sends the processed sound (through electromagnetic induction) to a receiver beneath the skin. Signals are then sent to an array of electrodes running through the cochlea. CIs can generally be more effective when implanted in people who have recently lost their hearing or in children with hearing impairments at a very early age (before the age of two). For an older person who has had hearing impairment for a long time or since birth, the brain may have great difficulty adapting to this new sensory input.

Early research on CIs included French-Algerian surgeons André Djourno and Charles Eyries placing a wire on an auditory nerve exposed during surgery in 1957. When a current was applied, the patient with hearing impairment heard sounds resembling a "roulette wheel" and a "cricket" . 

Although the early devices could not be used to understand speech, they helped with lip-reading.

In 1977, American engineer Adam Kissiah received a fundamental United States patent for stimulating human acoustic nerves with digital electronics.

Description of the Article Image: An illustration of electroacoustic stimulation in an ear, combining a hearing aid with a cochlear implant. An array of electrodes spirals through the cochlea.

Historical Figures Mentioned in This Article: André Djourno (1904–1996), Charles Eyries (1908–1996), Adam M. Kissiah Jr. (b. 1947)  

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