Hypothesis: The addition of a continuous, unmodulated, high-rate pulse train to sinusoidal stimuli presented by the cochlear implant to implant recipients will result in increases in the psychophysical dynamic range.
Background: The hearing dynamic range of cochlear implant patients is markedly reduced compared with that of normal-hearing individuals. This has negative implications for both speech perception and sound quality in these patients. It has been suggested that the addition of an unmodulated high-rate pulse train to deafened auditory nerves could create spontaneous-like neural activity, similar to that recorded from normal ears, of which one significant benefit would be an increase in the dynamic range of cochlear implant users.
Methods: Twenty-nine patients who underwent implantation with the Clarion CII device participated in this single-blinded prospective study. The psychophysical dynamic range of 28 of these subjects was measured with sinusoidal stimuli in response to various levels of an additional unmodulated high-rate pulse train.
Results: All the tested subjects (n = 28) demonstrated an increase in dynamic range in response to an appropriate level of unmodulated high-rate pulse train. The largest increase in dynamic range for each subject had a mean value of 6.7 dB.
Conclusion: The addition of an unmodulated high-rate pulse train to the electric signal presented to cochlear implant patients results in significant increases in dynamic range for sinusoidal stimuli.