I undertook personal research in 1967 to answer the question, Could electrical stimulation of the auditory nerve reproduce the frequencies of speech through temporal or place coding as well as the coding of intensity?
Thus it was important to know whether electrical current could be adequately localized to separate groups of auditory nerve fibers in the cochlea for place coding mid to high frequencies of speech, because these are specially relevant to understanding consonants.
These studies just mentioned, outlined in more detail by Clark [1,14], have demonstrated that even with multichannel stimulation, an electroneural "bottleneck" (Figure 8) was displayed at the interface between sound and the auditory pathways, limiting the rate and place coding of frequency and intensity.
Place coding, in particular, required multichannel stimulation and was best achieved with electrodes placed inside the cochlea .
The second question was, What were the right mechanical properties required for an electrode bundle to pass upward far enough without trauma around the scala tympani and lie opposite the auditory nerves and transmit speech frequencies on a place coding basis?
The receiver-stimulator enabled frequencies to stimulate appropriate electrodes to provide 10 to 15 channels of stimulation for the place coding of frequency.
In particular, I had a keen interest to see the relative importance of the place coding of frequency.
At least 10 perceptually distinct channels for the place coding of speech frequencies were found.
Rate of stimulation was retained across each of the electrodes stimulated with F2 and was consistent with the experimental animal behavioral studies [24,26], which demonstrated that temporal and place coding information was processed separately.