Study

Bilateral cochlear implants aim to provide hearing to both ears for children who are deaf and promote binaural/spatial hearing. Benefits are limited by mismatched devices and unilater-ally-driven development which could compromise the normal integration of left and right ear input. We thus asked whether children hear a fused image (ie. 1 vs 2 sounds) from their bi-lateral implants and if this “binaural fusion ” reduces listening effort. Binaural fusion was as-sessed by asking 25 deaf children with cochlear implants and 24 peers with normal hearing whether they heard one or two sounds when listening to bilaterally presented acoustic click-trains/electric pulses (250 Hz trains of 36 ms presented at 1 Hz). Reaction times and pupil-lary changes were recorded simultaneously to measure listening effort. Bilaterally implanted children heard one image of bilateral input less frequently than normal hearing peers, partic-ularly when intensity levels on each side were balanced. Binaural fusion declined as brain-stem asymmetries increased and age at implantation decreased. Children implanted later had access to acoustic input prior to implantation due to progressive deterioration of hear-ing. Increases in both pupil diameter and reaction time occurred as perception of binaura