In May 1964, Blair Simmons and a Stanford University colleague implanted a 6-electrode array into the modiolus of a 60-year-old volunteer subject who was totally deaf in the right ear and was losing his hearing in the left ear. Suffering from retinitis pigmentosa, the subject was also losing his sight. 

“We were amazingly lucky,” Blair Simmons commented later. “All electrodes functioned and remained so until he was explanted 18 months later” (Simmons, 1985). The subject could identify sound as speech by recognizing low sound frequencies, the time patterns, and some variation in loudness, but he could not identify individual words or phrases.

The paper in which Simmons (1965) reported this work, published in Science, recounts a series of experiments done with this subject. Many of these experiments concern the subject’s ability to discriminate stimuli that differed either in the location of the electrode stimulated (”place encoding”) or in the number of pulses per second provided (“rate encoding”).