Brain voice processing with bilateral cochlear implants: a positron emission tomography study.

Most cochlear implantations are unilateral. To explore the benefits of a binaural cochlear implant, we used water-labelled oxygen-15 positron emission tomography. Relative cerebral blood flow was measured in a binaural implant group (n = 11), while the subjects were passively listening to human voice sounds, environmental sounds non-voice or silence. Binaural auditory stimulation in the cochlear implant group bilaterally activated the temporal voice areas, whereas monaural cochlear implant stimulation only activated the left temporal voice area. Direct comparison of the binaural and the monaural cochlear implant stimulation condition revealed an additional right temporal activation during voice processing in the binaural condition and the activation of a right fronto-parietal cortical network during sound processing that has been implicated in attention. These findings provide evidence that a bilateral cochlear implant stimulation enhanced the spectral cues associated with sound perception and improved brain processing of voice stimuli in the right temporal region when compared to a monaural cochlear implant stimulation. Moreover, the recruitment of sensory attention resources in a right fronto-parietal network allowed patients with bilateral cochlear implant stimulation to enhance their sound discrimination, whereas the same patients with only one cochlear implant stimulation had more auditory perception difficulties.