| Effect of stimulus and recording parameters on spatial spread of excitation and masking patterns obtained with the electrically evoked compound action potential in cochlear implants. | |
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MedLine Citation:
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PMID: 20505513 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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OBJECTIVES: Spread of excitation within the cochlea in response to electrical stimulation can be measured with the electrically evoked compound action potential (ECAP). Different spread of excitation measurement techniques have been reported in the literature. One method uses a fixed stimulus location while varying the recording electrode along the length of the implanted array. This results in a relatively coarse estimate of spatial spread (SS) along the cochlea. Another method uses a forward-masking paradigm to evaluate the relative overlap of stimulated neural populations between electrodes. Both the probe and recording electrodes are fixed in location while a masker stimulus is systematically applied across electrodes. This method, which yields a more precise estimate of spatial excitation patterns, is termed spatial masking (SM). Five experiments were conducted to examine potential effects of stimulus and/or recording parameters on SS and SM patterns. Experiment 1 examined whether SS patterns were systematically broader than SM patterns across electrodes and subjects. Experiments 2 and 3 evaluated the effects of stimulus level on SS and SM patterns, respectively, to determine whether increased stimulus level systematically resulted in broader patterns. Experiment 4 evaluated whether recording electrode location affected SM patterns, and Experiment 5 evaluated whether SM patterns varied significantly across repeated trials within a test session. DESIGN: Data were collected for 27 ears in 26 adult and teenage subjects (N = 6 ears with Advanced Bionics CII, N = 8 ears with Advanced Bionics HiRes 90K, N = 10 ears with Nucleus 24R[CS], N = 3 ears with Nucleus 24RE[CA] Freedom). A standard forward-masking subtraction paradigm was used for all ECAP measures. For SS patterns, the masker and probe were fixed on the same electrode at the same level while the recording electrode varied across the remaining electrodes in the array. For SM patterns, the probe and recording locations were fixed while the masker location varied across all electrodes except the recording electrode. RESULTS: In experiment 1, SS patterns were broader than SM patterns. Subjects with Advanced Bionics devices exhibited relatively broad patterns for both measures, whereas Nucleus subjects typically exhibited narrower SM functions relative to SS functions. In experiments 2 and 3, there was a significant effect of stimulus level on the spread of both SS and SM patterns in roughly one-third of measures in each experiment. In experiment 4, there was a significant effect of recording electrode location on the width/spread of SM patterns for only 11.5% of comparisons. In experiment 5, there were no significant differences in SM amplitudes across repeated trials for 94% of comparisons, which suggests that ECAP measures are highly robust within a test session. CONCLUSIONS: Results showed that SS functions were generally broader than SM functions, which suggests that SS measures reflect volume conduction of the ECAP response along the length of the cochlea. Differences in the spread of SM functions across devices are likely due to differences in modiolar proximity between the respective electrode array designs. Stimulus level had a more significant effect on the spread of SM functions than recording electrode location. Finally, ECAP measures were shown to be highly stable across repeated measurements within a test session; however, repeatability was not assessed across sessions or over extended time intervals. |
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Authors:
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Michelle L Hughes; Lisa J Stille |
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Publication Detail:
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Type: Journal Article; Research Support, N.I.H., Extramural |
Journal Detail:
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Title: Ear and hearing Volume: 31 ISSN: 1538-4667 ISO Abbreviation: Ear Hear Publication Date: 2010 Oct |
Date Detail:
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Created Date: 2010-09-02 Completed Date: 2011-01-04 Revised Date: 2012-04-27 |
Medline Journal Info:
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Nlm Unique ID: 8005585 Medline TA: Ear Hear Country: United States |
Other Details:
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Languages: eng Pagination: 679-92 Citation Subset: IM |
Affiliation:
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Boys Town National Research Hospital, Lied Learning and Technology Center, Omaha, Nebraska 68131, USA. michelle.hughes@boystown.org |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Action Potentials
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physiology* Adolescent Adult Aged Child Cochlea / physiology* Cochlear Implants* Electric Impedance Electric Stimulation Electrodes, Implanted* Humans Middle Aged Models, Biological Perceptual Masking / physiology* Psychoacoustics |
| Grant Support | |
ID/Acronym/Agency:
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P30 DC004662-069002/DC/NIDCD NIH HHS; P30 DC04662/DC/NIDCD NIH HHS; R03 DC007017/DC/NIDCD NIH HHS; R03 DC007017-01A1/DC/NIDCD NIH HHS |
| Comments/Corrections | |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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