Experience with bilateral cochlear implants improves sound localization acuity in children.

HYPOTHESIS: Because of auditory plasticity, there can be experience-dependent acquisition and refinement of spatial hearing skills.

BACKGROUND: A growing number of children who are deaf are receiving bilateral cochlear implants (CIs), in an attempt to provide them with acoustic cues known to be important for spatial hearing. A feasible and reliable task for children is the right-left discrimination task, which enables measurement of the smallest angle from midline that can be reliably discriminated (minimum audible angle [MAA]).

METHODS: Ten children (5-10 yr of age) were followed longitudinally during their transition from 1 to 2 CIs, with testing before bilateral activation, as well as 3 and 12 months after bilateral activation. Testing at 3 and 12 months after bilateral activation was conducted under bilateral and first CI listening modes. During testing, stimuli were presented from an array of loudspeakers. On each trial, the child reported whether the sound was to the right or left, with feedback. Percent correct was measured in blocks of trials for numerous angle values.

RESULTS: At baseline, some children were unable to perform the right-versus-left task, but group mean MAA was 44.8 degrees. MAA in the bilateral listening mode improved to 20.4 degrees at 3 months and 16.8 degrees at 12 months after bilateral activation. No improvement was seen in the unilateral listening mode. Bilateral performance was better than unilateral.

CONCLUSION: Spatial hearing skills in sequentially implanted children develop in an experience-dependent manner, perhaps because of the ability of the auditory system to use newly acquired electrical stimulation presented to the 2 ears.