Binaural and Spatial Hearing in Implanted Children

The ability to hear and communicate in everyday, complex acoustic environments depends on how well the auditory system can utilize binaural hearing mechanisms, which requires integration of inputs arriving at the two ears, facilitating sound source localization and separation of speech from background noise. This chapter reviews and discusses the potential benefits from having inputs to ears, when listeners rely on acoustic hearing, or electric hearing through cochlear implants (CIs). Nowadays, it is common for children who are deaf to receive bilateral cochlear implants (BiCIs). At the start of the millennium, this clinical approach was somewhat novel and considered to be lacking in evidence regarding benefits. However, the clinical trend has shown momentum toward bilateral stimulation. This chapter reviews acoustic cues that are necessary for binaural hearing to occur, namely interaural differences in time and level. Methods used to evaluate whether young children can use binaural cues are described, focusing on how we study sensitivity to binaural cues, sound localization, and speech understanding in noise. Young children today are fitted with hearing aids and/or CIs so that language acquisition and verbal communication can be developed, ideally at age-appropriate levels. CIs were designed to provide the signal processing necessary for stimulating the auditory nerve so that patients could hear speech, in quiet and in noise, but bilateral CIs were not designed to encode binaural cues. Future work will ideally focus on providing better understanding of how to continue to maximize outcomes in bilaterally implanted children.