Effects of parameter manipulations on spread of excitation measured with electrically-evoked compound action potentials.
OBJECTIVE
This study investigated the spread of excitation (SOE) profiles derived by eCAP measures and analysed the effects of various parameter settings.


METHODS
SOE was measured using the forward masking technique (selectivity), as well as with a "fixed stimulus, variable recording" (scanning) technique. SOE profiles were produced at three current levels and at three sites along the array. Additionally, effects of the position of the recording electrodes and artefact rejection methods were studied in five subjects. Furthermore, correlation between SOE data and speech perception data was tested. All data were analysed using linear mixed models.


METHODS
Measurements were performed intraoperatively in 31 users of the Advanced Bionics HiRes 90K cochlear implant.


RESULTS
The selectivity method produced narrower excitation profiles than the scanning method, showing an asymmetry along the array with wider SOE apically. Moreover, the position of the recording electrode shifted the SOE curves towards the recording contact, enhancing asymmetry. Neither significant effects of current level or artefact rejection methods were observed, nor a significant correlation with speech perception.


CONCLUSIONS
SOE profiles obtained with the scanning method are wider than with the selectivity method. Both are insensitive to various parameter settings, although selectivity curves are shifted towards the recording contact.
Department of Otolaryngology, Leiden University Medical Center, The Netherlands. beek@lumc.nl
Feddo B
FB
van der Beek
Jeroen J
JJ
Briaire
Johan H M
JH
Frijns
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D002648:Child; D002675:Child, Preschool; D019929:Cochlear Implantation / Q000295:instrumentation*; D003054:Cochlear Implants; D003056:Cochlear Nerve / Q000503:physiopathology*; D032882:Comprehension; D012048:Correction of Hearing Impairment / Q000523:psychology; D003638:Deafness / Q000503:physiopathology / Q000523:psychology / Q000534:rehabilitation*; D004558:Electric Stimulation; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D007223:Infant; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D019986:Persons with Hearing Disabilities / Q000523:psychology / Q000534:rehabilitation*; D011474:Prosthesis Design; D012815:Signal Processing, Computer-Assisted; D013063:Speech Discrimination Tests; D013065:Speech Intelligibility; D013067:Speech Perception; D013997:Time Factors; D055815:Young Adult