Q J Fu1, R V Shannon. 1. Department of Auditory Implants and Perception, House Ear Institute, Los Angeles, California 90057, USA.
Abstract
OBJECTIVE: This study was conducted to understand vowel recognition in cochlear implants as a function of the cochlear location and separation of the stimulated electrode pairs and as a function of the matching between speech spectral information and the location of the stimulated electrodes. DESIGN: Four-electrode speech processors with a continuous interleaved sampling speech processing strategy were implemented through a custom interface in five subjects implanted with the Nucleus-22 cochlear implant. The temporal envelopes from four broad frequency bands were used to modulate 500 pps, 100 microsec/phase interleaved pulse trains delivered to four electrode pairs. Ten different frequency allocations and five sets of four-electrode configurations were tested. Each frequency allocation represented the same cochlear extent but different cochlear locations based on Greenwood's frequency-to-place formula. Recognition of multi-talker medial vowels was measured for each combination of parameters with no period of practice or adjustment. RESULTS: Results showed that recognition of multi-talker vowels was highly dependent on frequency allocation for all electrode configurations. For a given electrode configuration maximum vowel recognition was observed with a specific frequency allocation. When the stimulated electrodes were shifted basally by 3 mm, the frequency allocation that produced the best performance also shifted basally by 3 mm. A similar pattern of vowel recognition was observed as a function of frequency allocation for electrode configurations that had the same apical-most electrode in each pair, regardless of location of the basal-most electrode in the pair. Subjects with different electrode insertion depths had similar trends in vowel recognition for each frequency allocation. CONCLUSIONS: For a given electrode configuration, the best performance was obtained with processors with a specific frequency allocation. In addition, the apical-most member of each electrode pair had a much stronger influence on vowel recognition in electric hearing. Finally, results from this study also suggest that over time, patients with implants can partially adapt to a basal shift in place of stimulation.
OBJECTIVE: This study was conducted to understand vowel recognition in cochlear implants as a function of the cochlear location and separation of the stimulated electrode pairs and as a function of the matching between speech spectral information and the location of the stimulated electrodes. DESIGN: Four-electrode speech processors with a continuous interleaved sampling speech processing strategy were implemented through a custom interface in five subjects implanted with the Nucleus-22 cochlear implant. The temporal envelopes from four broad frequency bands were used to modulate 500 pps, 100 microsec/phase interleaved pulse trains delivered to four electrode pairs. Ten different frequency allocations and five sets of four-electrode configurations were tested. Each frequency allocation represented the same cochlear extent but different cochlear locations based on Greenwood's frequency-to-place formula. Recognition of multi-talker medial vowels was measured for each combination of parameters with no period of practice or adjustment. RESULTS: Results showed that recognition of multi-talker vowels was highly dependent on frequency allocation for all electrode configurations. For a given electrode configuration maximum vowel recognition was observed with a specific frequency allocation. When the stimulated electrodes were shifted basally by 3 mm, the frequency allocation that produced the best performance also shifted basally by 3 mm. A similar pattern of vowel recognition was observed as a function of frequency allocation for electrode configurations that had the same apical-most electrode in each pair, regardless of location of the basal-most electrode in the pair. Subjects with different electrode insertion depths had similar trends in vowel recognition for each frequency allocation. CONCLUSIONS: For a given electrode configuration, the best performance was obtained with processors with a specific frequency allocation. In addition, the apical-most member of each electrode pair had a much stronger influence on vowel recognition in electric hearing. Finally, results from this study also suggest that over time, patients with implants can partially adapt to a basal shift in place of stimulation.
Authors: Michael F Dorman; Tony Spahr; Rene Gifford; Louise Loiselle; Sharon McKarns; Timothy Holden; Margaret Skinner; Charles Finley Journal: J Assoc Res Otolaryngol Date: 2007-03-10
Authors: Charles C Finley; Timothy A Holden; Laura K Holden; Bruce R Whiting; Richard A Chole; Gail J Neely; Timothy E Hullar; Margaret W Skinner Journal: Otol Neurotol Date: 2008-10 Impact factor: 2.311