Review of recent work on spatial hearing skills in children with bilateral cochlear implants

Review of recent studies on spatial-hearing abilities in children who use bilateral cochlear implants (BiCIs); compare performance of children who use BiCIs with children who have normal hearing.

Results from recent studies are reviewed in two categories. First, studies measured spatial hearing by using sound localization or identification methods, thereby focusing on localization accuracy. Second, studies that measured the ability of children to discriminate between sound source positions in the horizontal plane, thereby focusing on localization acuity where performance was quantified using the minimum audible angle (MAA).

Children with BiCIs have localization errors that vary widely. There is evidence that for many children errors are smaller when using two vs. one implant. In the bilateral condition, some children's performance falls within the range of errors seen in children with normal hearing (less than 30° root mean square), but most children have errors that are significantly greater than those of children with normal hearing. On MAA tasks, performance is generally significantly better (lower MAAs) when children are tested in the bilateral listening mode than in the unilateral listening mode. However, MAAs are generally higher than those measured in children with normal hearing.

Results are discussed in the context of auditory experience, and also with regard to the lack of availability of binaural cues presented through the CI speech processors when the children are using their processors in everyday listening situations. The potential roles of interaural timing vs. level cues are discussed.