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Binaural sensitivity as a function of interaural electrode position with a bilateral cochlear implant user
Christopher J Long1, Donald K Eddington, H Steven Colburn
1Speech and Hearing Sciences Program, Division of Health Sciences and Technology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA. stoph@alum.mit.edu
The Journal of the Acoustical Society of America
|September 30, 2003
Summary
Bilateral cochlear implant users can perceive sound location using interaural time difference (ITD) and interaural level difference (ILD) cues. Electrode pairing significantly impacts ITD sensitivity, offering hope for improved binaural hearing in implant users.
Area of Science:
- Neuroscience
- Audiology
- Biomedical Engineering
Background:
- Bilateral cochlear implants aim to restore binaural hearing, but understanding the underlying acoustic cues is crucial for optimizing device efficacy.
- Interaural Time Difference (ITD) and Interaural Level Difference (ILD) are key binaural cues for sound localization and speech perception.
Observation:
- A single bilateral cochlear implant user was tested using custom equipment to control ITD and ILD stimuli.
- A lateralization task assessed the perceived location of auditory sensations elicited by varying ITD and ILD.
- Electrode pairing significantly influenced the user's sensitivity to ITD, with similar electrode pitches correlating with ITD sensitivity.
Findings:
- The user demonstrated sensitivity to ITDs as small as 300 microseconds, confirming access to binaural information.
- Specific electrode pairs enabled significant auditory image shifts with ITDs (300-600 µs) and ILDs (~11% dynamic range).
- Even electrode pairs without significant ITD sensitivity showed responses to interaural level cues.
Implications:
- Electrode selection is critical for maximizing binaural advantages in bilateral cochlear implant systems.
- These findings suggest that bilateral cochlear implants can potentially provide normal binaural hearing benefits, including improved speech recognition and sound localization.
- Further research is needed to generalize these findings to a broader population of bilateral cochlear implant users.