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Localization by postlingually deafened adults fitted with a single cochlear implant
D Wesley Grantham1, Todd A Ricketts, Daniel H Ashmead
1Department of Hearing & Speech Sciences, Vanderbilt Bill Wilkerson Center for Otolaryngology and Communication Sciences, Vanderbilt University Medical Center, 1215 21st Avenue South, Nashville, TN 37232, USA. d.wesley.grantham@vanderbilt.edu
The Laryngoscope
|November 3, 2007
Summary
Adults with unilateral cochlear implants showed varied sound localization skills. Some improved beyond chance using monaural cues, but performance lagged behind bilateral implant users.
Area of Science:
- Audiology
- Neuroscience
- Biomedical Engineering
Background:
- Cochlear implants (CIs) restore hearing but spatial hearing remains a challenge.
- Unilateral CIs offer sound input to only one ear, limiting binaural cue utilization.
Purpose of the Study:
- To evaluate the horizontal plane sound localization abilities of adults with unilateral cochlear implants.
- To determine if unilateral CI users can localize noise and speech signals.
Main Methods:
- Six postlingually deafened adults with unilateral MED-EL COMBI 40+ CIs participated.
- A modified source identification task was used in an anechoic chamber with 43 loudspeakers.
- Subjects identified the source of brief noise or speech signals presented from different locations.
Main Results:
- Localization performance varied, with three subjects near chance (50.5° error) and three significantly better (35°-44° error).
- Normal-hearing listeners achieved a 5.6° error.
- Two subjects utilized monaural cues, likely frequency-dependent head-shadow effects, for improved localization.
Conclusions:
- Some individuals with unilateral CIs can achieve better-than-chance sound localization.
- Learned use of monaural cues contributes to this improved performance.
- Unilateral CI performance is substantially poorer than that of bilaterally implanted individuals who leverage binaural cues.
