Many profoundly deafened people have benefited from cochlear implant in the past twenty years. Speech perception provided by cochlear implants has proven to be quite successful. It is still a challenge, however, to perceive music or lexical tone in tone languages with the current cochlear implant system. That is because the low spectral resolution in the electric stimulation provided by only a few electrodes prevents pitch information from being transmitted. The present research project is proposed to examine the possible benefits that bilateral implantation provides for increasing spectral resolution, hence improving music and tone perception. With a bilateral implant, an input signal can be analyzed with more frequency bands, the number of which equals the total number of electrodes in both implants. The channels are to be dichotically distributed, that is, the odd-index channels are assigned to one ear, and the even-index channel assigned to the other. Each electrode in both implants therefore receives exclusive but twice as refined spectral information. This new strategy doubles spectral resolution in bilateral implants compared to traditional bilateral implants that are assigned with same channels or repeated spectral information. The proposed new strategy will be simulated using a noise-excited vocoder and validated in bilateral implant patients.
The specific aims of the study are (1) to evaluate how much music and tone perception benefits from the new strategy that doubles spectral resolution via dichotic stimulation;and (2) to test how well the dichotically presented stimuli fuse under conditions in which the relative position of the two implants is manipulated. For music perception, a traditional familiar melody recognition test will be used. In addition, a modified melody test will be used, in which the listeners are required to detect pitch changes made to particular notes in a melody. For lexical tone perception, a four-alternative forced choice paradigm will be used. Speech tests (i.e., consonant and vowel recognition tests) will also be included in both specific aims. The results of the present study will further our knowledge regarding the mechanisms of spectral fusion of complex signals in both acoustic and electric hearing. The success of this strategy will greatly improve music and tone perception with bilateral implantation, hence considerably improving the life quality of bilateral implant users.
| Wang, Wuqing; Zhou, Ning; Xu, Li (2011) Musical pitch and lexical tone perception with cochlear implants. Int J Audiol 50:270-8 |
| Zhou, Ning; Xu, Li; Lee, Chao-Yang (2010) The effects of frequency-place shift on consonant confusion in cochlear implant simulations. J Acoust Soc Am 128:401-9 |
