Extracochlear electrical stimulation

Twelve patients with sensorineural hearing loss were stimulated by a transtympanic electrode contacting the cochlear promontory. Nine of them were tested to study hearing perception associated with various features of electrical signals, using an auditory electrical stimulator. Biphasic pulse bursts and sine-wave bursts were used as stimuli. Different electrical characteristics such as amplitude, width and rate for pulses and amplitude and frequency for sine waves were used to investigate hearing perception. The patients' perception threshold, comfortable level, uncomfortable level, dynamic range, just-noticeable difference in frequency or pitch discrimination, just-noticeable difference in intensity or loudness discrimination, loudness perception associated with the electrical signal energy, and sounds associated with electrical stimulation was determined. Pertinent results assisted in the development of a speech electrical stimulator that was used to test three patients for vowel, word, and consonant identification and recognition of patterns of intonation. These results in turn are being used to design a prototype of a single-channel extracochlear prosthesis.