Voice discrimination in cochlear-implanted deaf subjects

The human voice is important for social communication because voices carry speech and other information such as a person's physical characteristics and affective state. Further restricted temporal cortical regions are specifically involved in voice processing. In cochlear-implanted deaf patients, the processor alters the spectral cues which are crucial for the perception of the paralinguistic information of human voices. The aim of this study was to assess the abilities of voice discrimination in cochlear-implant (CI) users and in normal-hearing subjects (NHS) using a CI simulation (vocoder). In NHS the performance in voice discrimination decreased when reducing the spectral information by decreasing the number of channels of the vocoder. In CI patients with different delays after implantation we observed a strong impairment in voice discrimination at time of activation of the neuroprosthesis. No significant improvement can be detected in patients after two years of experience of the implant while they have reached a higher level of recovery of speech perception, suggesting a dissociation in the dynamic of functional recuperation of speech and voice processing. In addition to the lack of spectral cues due to the implant processor, we hypothesized that the origin of such deficit could derive from a crossmodal reorganization of the temporal voice areas in CI patients.