Binaural Stimulation Through Cochlear Implants in Postlingual Deafness: A Positron Emission Tomographic Study of Word Recognition

Hypothesis: Bilateral stimulation through cochlear implants induces a brain activity pattern closer to the normal one than unilateral stimulation. Background: Although it has been shown that speech comprehension through bilateral cochlear implants leads to better performances than after unilateral implantation, the existence of neural underpinnings of this improvement remains to be studied. Methods: We performed an H2O15 positron emission tomographic study of word recognition in 5 patients with bilateral cochlear implants and 5 normal-hearing controls. Subjects had to distinguish words from nonwords in binaural and monaural conditions. Results: There was no overactivation in patients for binaural stimulation, with a hypoactivation in the right temporal cortex. For monaural stimulation, patients demonstrated more activation contralaterally to the stimulation side in the posterior temporal cortex and in the cerebellum. Conclusion: Binaural stimulation through cochlear implants is advantageous compared with the monaural at the neurofunctional level because the pattern of brain activity is closer to the normal one.