DOI: 10.5061/dryad.0m09h
title: Data from: Development of sound localization strategies in children with bilateral cochlear implants

description: 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.
description: Stimulus WAVE Files used
 in localization taskStimuli consisted of
 bi-syllabic Children’s Spondees that have been previously used for studies
 on spatial unmasking of speech in children with NH [14], and with
 BiCIs[15], recorded with a male voice at a sampling rate of 44 kHz. The
 speech corpus had 25 words. On each trial one of the words was randomly
 chosen from the list, with replacement. Thus, on any given trial the
 stimulus was unpredictable, thereby reducing the availability of reliable
 spectral cues that might be used in the computation of sound source
 location. Stimuli were balanced for loudness using equal root-mean-square
 levels for all words. Stimuli were amplified and sent to the loudspeakers
 via Tucker Davis Technologies System III hardware. Stimulus levels
 averaged 60 dB SPL, with a random variation between 56 and 64 dB SPL (±4
 dB) from trial to trial to minimize the availability of overall level
 cues.Stimulus
 Files.zipMatLab code used to
 calculate and plot Localization SensitivityAnalyses of localization
 sensitivity employed a statistical non-parametric Kruskal-Wallis test to
 examine the relative independence of responses to each stimulus location,
 given a single response to an unknown stimulus. For each pair of locations
 in the loudspeaker array, the two response groups were analyzed using
 pairwise localization sensitivity index (LSI) values based on the z-scores
 from the p-value obtained bythe non-parametric Kruskal-Wallis test. The
 analysis produces a matrix of LSIs in coordinates of response locations.
 For N=15 target locations, the total number of LSI values was 105
 [15*(15-1)/2=105]. The matrix is symmetrical about the diagonal. The
 matrixwas interpolated via the MATLAB contour function to find a contour
 of LSI with a z score of 1.65 (the 95th confidence level as the
 statistical threshold indicative of two locations being perceptually
 differentiated). We defined the contour of LSI = 1.65 as the sensitivity
 threshold. The overall localization sensitivity (LS) was characterized for
 individuals by averaging LSIs in the LSI matrix.analysis.txt