Abstract
The ability to determine a sound’s location is critical in everyday life. However, sound source localization is severely compromised for patients with hearing loss who receive bilateral cochlear implants (BiCIs). Several patient factors relate to poorer performance in listeners with BiCIs, associated with auditory deprivation, experience, and age. Critically, characteristic errors are made by patients with BiCIs (e.g., medial responses at lateral target locations), and the relationship between patient factors and the type of errors made by patients has seldom been investigated across individuals. In the present study, several different types of analysis were used to understand localization errors and their relationship with patient-dependent factors (selected based on their robustness of prediction). Binaural hearing experience is required for developing accurate localization skills, auditory deprivation is associated with degradation of the auditory periphery, and aging leads to poorer temporal resolution. Therefore, it was hypothesized that earlier onsets of deafness would be associated with poorer localization acuity and longer periods without BiCI stimulation or older age would lead to greater amounts of variability in localization responses. A novel machine learning approach was introduced to characterize the types of errors made by listeners with BiCIs, making them simple to interpret and generalizable to everyday experience. Sound localization performance was measured in 48 listeners with BiCIs using pink noise trains presented in free-field. Our results suggest that older age at testing and earlier onset of deafness are associated with greater average error, particularly for sound sources near the center of the head, consistent with previous research. The machine learning analysis revealed that variability of localization responses tended to be greater for individuals with earlier compared to later onsets of deafness. These results suggest that early bilateral hearing is essential for best sound source localization outcomes in listeners with BiCIs.
Highlights
Cochlear implants (CIs) are designed to provide access to auditory information and to improve speech understanding for individuals with severe-to-profound hearing loss
The goal of the present study was to determine whether patient-dependent factors related to auditory deprivation, experience with CIs, and age were predictive of the amount of error and pattern of localization responses in listeners with bilateral CIs (BiCIs)
It was further hypothesized that longer periods of auditory deprivation, shorter periods of experience with BiCIs, and older age at testing would be associated with larger amounts of variability
Summary
Cochlear implants (CIs) are designed to provide access to auditory information and to improve speech understanding for individuals with severe-to-profound hearing loss. The addition of a second CI has the potential to provide benefits stemming from binaural hearing, such as localization of sounds sources in space, improved speech understanding in noise, and reduction in listening effort [1–3]. The present paper focuses on sound source localization and the factors that affect localization performance in patients with bilateral CIs (BiCIs). There is extensive literature documenting the impact of patient-dependent factors on localization error for listeners with BiCIs. Several factors associated with auditory deprivation and experience with BiCIs are predictive of sensitivity to cues used for localization, outlined by Thakkar and colleagues [4]. The goal of the present experiment was to determine the contribution of these factors to sound source localization by comparing differences in the pattern of localization responses
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