Developmental trajectories of binaural fusion in children with typical hearing, hearing aids, and cochlear implants

Binaural pitch fusion is the perception of sounds differing in frequency across the two ears as a single auditory object. Many listeners with hearing loss experience broad binaural fusion of tones and voice pitches differing by as much as three to four octaves, and such broad fusion limits their ability to segregate voices and understand speech in background noise. Here we present longitudinal data showing developmental trajectories of binaural fusion in children over the age range from 6–14 years old. Children with typical hearing, bilateral hearing aids, and bimodal cochlear implant (CI; worn with contralateral hearing aid) initially had broad binaural pitch fusion ranges compared to adults. With increasing age, binaural fusion ranges narrowed by one to three octaves for these groups. In contrast, no narrowing of binaural fusion was observed for children with bilateral CIs. Interaural pitch discrimination was also measured, but did not show changes with age, ruling out discrimination changes as an explanation for the binaural fusion range changes. The differences in the trajectory of binaural fusion across groups indicate the importance of hearing device combination for the development of binaural processing abilities in children with hearing loss, with implications for improving speech processing in noise. [Work supported by NIH/NIDCD R01DC013307.]