Spatial hearing of normally hearing and cochlear implanted children

Abstract

ObjectiveSpatial hearing uses both monaural and binaural mechanisms that require sensitive hearing for normal function. Deaf children using either bilateral (BCI) or unilateral (UCI) cochlear implants would thus be expected to have poorer spatial hearing than normally hearing (NH) children. However, the relationship between spatial hearing in these various listener groups has not previously been extensively tested under ecologically valid conditions using a homogeneous group of children who are UCI users. We predicted that NH listeners would outperform BCI listeners who would, in turn, outperform UCI listeners.MethodsWe tested two methods of spatial hearing to provide norms for NH and UCI using children and preliminary data for BCI users. NH children (n = 40) were age matched (6–15 years) to UCI (n = 12) and BCI (n = 6) listeners. Testing used a horizontal ring of loudspeakers within a booth in a hospital outpatient clinic. In a ‘lateral release’ task, single nouns were presented frontally, and masking noises were presented frontally, or 90° left or right. In a ‘localization’ task, allowing head movements, nouns were presented from loudspeakers separated by 30°, 60° or 120° about the midline.ResultsNormally hearing children improved with age in speech detection in noise, but not in quiet or in lateral release. Implant users performed more poorly on all tasks. For frontal signals and noise, UCI and BCI listeners did not differ. For lateral noise, BCI listeners performed better on both sides (within ∼2 dB of NH), whereas UCI listeners benefited only when the noise was opposite the unimplanted ear. Both the BCI and, surprisingly, the UCI listeners performed better than chance at all loudspeaker separations on the ecologically valid, localization task. However, the BCI listeners performed about twice as well and, in two cases, approached the performance of NH children.ConclusionChildren using either UCI or BCI have useful spatial hearing. BCI listeners gain benefits on both sides, and localize better, but not as well as NH listeners.

Development of Auditory Localization Accuracy and Auditory Spatial Discrimination in Children and Adolescents

“…Compared to the present data, mean absolute errors of localization were somewhat smaller (from 5° for 4-year-olds to 1° for 6-year-olds), but in this study the speakers were visible and positive feedback was provided for correct answers, which might have made the task easier as learning effects cannot be excluded. We can, therefore, reasonably assume that from 6 years onwards, no further improvement of localization accuracy occurs, as also shown by Murphy et al [2011].…”

Contrasting benefits from contralateral implants and hearing aids in cochlear implant users

“…The spatial hearing advantage in BiCI users is also reflected in the results from self-assessment questionnaires for both adults and children, although in the latter case the data are considerably noisier. The advantage appears not to be due to greater familiarity with the bilateral condition compared to the monaural condition when testing BiCI users because comparable improvements are seen relative to actual unilateral CI users (Dunn et al, 2010b;Murphy et al, 2011). The benefits available from a contralateral hearing aid in bimodal listeners are in contrast not strongly related to spatial hearing, and instead derive more from the provision of information that is unavailable through the cochlear implant.…”

European Bilateral Pediatric Cochlear Implant Forum Consensus Statement

“…However, these children have the benefit of developing bilateral auditory pathways in tandem (30,38Y40) without the risk that one side is strengthened at the expense of the other as exists when stimulation is provided unilaterally for extended periods. Early data suggest that these children show more normal bilateral listening abilities than their peers receiving bilateral implants sequentially (27,39) and that, when bilateral implants are provided early and simultaneously, speech and language skills develop rapidly (12). A study comparing 25 unilateral implanted children with 25 bilaterally implanted children (all implanted before 2.06 years of age and carefully matched) found that bilateral implants are associated with better spoken language learning and that a longer interval between implants adversely affected the scores (41).…”