[Electric stimulation of auditory nerve fibers. Experimental study]

The authors tested in animal experiments the effectiveness of electrical stimulation of acoustic nerve fibres. To guinea pigs platinum-iridium electrodes were implanted in the round window of the cochlea. The receptors of the inner ear were functionally eliminated by the local application of the ototoxic antibiotic gentamicin. Cortical responses produced by electric stimulation of the contralateral ear and acoustic stimulation of the ipsilateral intact ear were recorded. The threshold for producing a cortical response by the electric stimulus was lowest at the frequency of 0.5 kHz and rose with the rising frequency. This relationship was the same for extracochlear and intracochlear stimulation, the absolute threshold values of the current in the same animal were, however, as a rule lower on intracochlear stimulation. The dynamic range of responses to electrical stimulation (difference between threshold intensity of the current and the intensity which produces a painful response of the animal) was 6-20 dB, as compared with 80-100 dB of the dynamic range for acoustic stimulation. The results of the experiments were used in the preparation of the Czechoslovak cochlear neuroprosthesis and serve as a basis for the further development of the implant.