A neuro-imaging approach to evidencing bilateral cochlear implant advantages in auditory perception

摘要

Introduction Hearing loss is an auditory perception disorder that induces deficits in oral communication, mainly due to the lack of perception of acoustical cues useful for speech production and understanding. Patients have difficulties distinguishing speech and voice from other sounds, such as environmental noises. Individuals with hearing loss may benefit from cochlear implantation to improve voice and speech cues transduction. The functional results vary from restoration of sound perception to full speech intelligibility and voice recognition. Outcomes of implantation depend not only on the implant signal but also on its coupling to the central auditory system, and the ability of auditory and other related brain systems to learn how to most efficiently obtain information from that signal (Moore and Shannon, 2009). Although binaural perception is key for normal sound perception and although recent clinical studies demonstrate a bilateral advantage in speech intelligibility and sound localization in complex noisy environments (Mosnier et al, 2009), the majority of the 120 000 patients who benefit from cochlear implantation have only one cochlear implant. Studies on bilateral cochlear implants hardly justify the need for a second cochlear implant in order for rehabilitation to be achieved. Recent (H_2~(15)O) positron emission tomography (PET) activation studies suggest that PET is an adequate method for exploring cochlear implant benefits and that the advantage in speech understanding can be linked to the activation of the temporal voice area (Coez et al, 2008, 2009) located along the upper bank of the superior temporal sulcus (STS) bilaterally (Belin et al, 2000). In order to measure the benefit from two independent sites of cochlear stimulation provided by a bilateral cochlear implant compared to a unilateral one, we used PET (H_2~(15)O) to study temporal voice area activation.