Development of Sound Localization Strategies in Children with Bilateral Cochlear Implants

Abstract

Localizing sounds in our environment is one of the fundamental perceptual abilities that enable humans to communicate, and to remain safe. Because the acoustic cues necessary for computing source locations consist of differences between the two ears in signal intensity and arrival time, sound localization is fairly poor when a single ear is available. In adults who become deaf and are fitted with cochlear implants (CIs) sound localization is known to improve when bilateral CIs (BiCIs) are used compared to when a single CI is used. The aim of the present study was to investigate the emergence of spatial hearing sensitivity in children who use BiCIs, with a particular focus on the development of behavioral localization patterns when stimuli are presented in free-field horizontal acoustic space. A new analysis was implemented to quantify patterns observed in children for mapping acoustic space to a spatially relevant perceptual representation. Children with normal hearing were found to distribute their responses in a manner that demonstrated high spatial sensitivity. In contrast, children with BiCIs tended to classify sound source locations to the left and right; with increased bilateral hearing experience, they developed a perceptual map of space that was better aligned with the acoustic space. The results indicate experience-dependent refinement of spatial hearing skills in children with CIs. Localization strategies appear to undergo transitions from sound source categorization strategies to more fine-grained location identification strategies. This may provide evidence for neural plasticity, with implications for training of spatial hearing ability in CI users.

Does Bilateral Experience Lead to Improved Spatial Unmasking of Speech in Children Who Use Bilateral Cochlear Implants?

“…Similar differences between CI users and NH children were found by van Deun and colleagues[6]. More recently Zheng and colleagues [7] investigated emergence of sound localization skills in a group of 19 bilaterally implanted children, and reported that with additional experience listening through BiCIs, most children improve, as seen in reduced localization errors. The error types were further analyzed to better understand whether the pattern of errors change with experience.…”

“…Of the 20 children tested here, 11 were also tested on localization as reported by Zheng and colleagues [7], and for those children some comparisons are made between the speech-in-noise data and the localization results. This study sought to determine whether children demonstrate improvement on speech reception thresholds (SRTs), and/or on their ability to benefit from spatial separation of the target and interferers.…”

Binaural hearing in children using Gaussian enveloped and transposed tones

“…RMS localization errors are also generally better in the bilateral condition compared with the unilateral condition (GriecoCalub and Litovsky, 2010). However, even when using BiCIs, these children show significantly poorer performance compared to their NH age-matched peers; this gap in performance is observed even after several years of experience with BiCIs (Zheng et al, 2015).…”

Bilateral cochlear implants in children: Effects of auditory experience and deprivation on auditory perception

“…For recent reviews on this topic see also [5, 6]. A second measure is localization accuracy, which is informative regarding the ability of a listener to identify the location of a sound source from amongst an array of sources; accuracy can be measured for sound sources along the vertical or horizontal dimension but in bilateral CI users the focus has been on the horizontal plane, where binaural cues would be most effectively utilized [11]. Figure 1 summarizes data from recent studies in which acuity and accuracy were measured in children with bilateral CIs.…”