Investigations on the tonotopy for patients with a cochlear implant and a hearing aid.

OBJECTIVE: The aim of investigations was to compare the perception of the pitch of tonal signals by patients using both the cochlear implant and hearing aid. MATERIAL AND METHOD: The subjective evaluation of the pitch of sound presented through classical acoustic amplification and perceived by the residual hearing was compared with the sound perceived as a result of an electric stimulation. The subjects were 6 patients aged 15-63 (mean 38), diagnosed with postlingual deafness. The comparison of the acoustic signal transmitted via the hearing aid (in the acoustic free field) with the electrical signal from stimulated electrode of the cochlear implant enabled to determine subjectively evaluated shift in the frequency domain. The tonotopic distribution according to the Greenwood's model compared with the allocation of frequency determined on the basis of cochlear view was also investigated. RESULTS AND CONCLUSION: The study has revealed significant differences in the perception of the pitch of sounds perceived through the acoustic stimulation via the hearing aid and the electric stimulation via the implant.