Effect of degraded binaural cues in cochlear implant users and normal hearing listeners on spatial release from masking

Abstract

Bilateral cochlear implants (BiCIs) are being provided to a growing number of individuals with bilateral severe-profound hearing loss and are becoming standard in many clinics worldwide, to restore spatial hearing skills and improve speech understanding in noisy environments. While patients generally perform better with BiCIs, their performance is significantly worse than that of normal hearing (NH) listeners. Spatial release from masking (SRM) in NH listeners depends on monaural (head shadow) and binaural cues. In BiCI users, SRM appears to be primarily due to head shadow; however, binaural-mediated SRM is weak or absent. Two factors are most likely responsible for this. First, bilateral CI processors are not coordinated, rendering binaural cues weak, absent or inconsistent. Second, patients' history with auditory deprivation likely results in poor neural survival at numerous cochlear locations. Our studies suggest that signal processing tools can be applied to bilateral CI users to restore binaural sensitivity. In this talk, data will be presented from studies with adults and children, in free field and using binaural research processors. Results from studies on restoration of interaural level and timing differences to BiCI users will be discussed in the context of what is needed for binaural SRM restoration. Work supported by NIH-NIDCD (grants 5R01DC003083 and 5R01DC8365)