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Updated: Dec 2, 2025
Optogenetic Stimulation of the Auditory Nerve
Published on: October 8, 2014
Effect of Increasing Pulse Phase Duration on Neural Responsiveness of the Electrically Stimulated Cochlear Nerve
Shuman He1,2, Lei Xu3, Jeffrey Skidmore1
1Department of Otolaryngology - Head and Neck Surgery, The Ohio State University, Columbus, Ohio, USA.
Insights
Increasing pulse phase duration (PPD) did not significantly alter cochlear nerve (CN) responses in children with cochlear nerve deficiency (CND) or normal CNs. This study compared eCAP responses in children with CND versus normal CNs.
Area of Science:
- Neuroscience
- Biomedical Engineering
- Audiology
Background:
- Cochlear nerve deficiency (CND) affects auditory nerve function in pediatric cochlear implant users.
- Understanding neural responses to electrical stimulation is crucial for optimizing cochlear implant performance.
Purpose of the Study:
- To investigate the impact of varying pulse phase duration (PPD) on electrically evoked compound action potential (eCAP) responses in the cochlear nerve (CN) of children with CND.
- To compare these neural responses with those from children possessing normal-sized CNs.
Main Methods:
- Electrically evoked compound action potential (eCAP) input/output (I/O) functions were recorded in 30 children with CND and 30 controls using Cochlear Nucleus devices.
- Different PPDs (50-88 μsec/phase) were tested at three electrode locations, measuring eCAP amplitude, threshold, and I/O function slope.
- Generalized linear mixed effect models analyzed the effects of PPD, electrode location, and study group on eCAP parameters.
Main Results:
- Children with CND exhibited significantly smaller eCAP amplitudes, higher eCAP thresholds, and flatter eCAP I/O function slopes compared to controls.
- Within the CND group, fewer electrodes with measurable eCAPs correlated with smaller amplitudes and flatter slopes.
- Increasing PPD did not yield statistically significant changes in eCAP amplitude, threshold, or slope in either group.
Conclusions:
- Pulse phase duration adjustments did not significantly alter cochlear nerve responsiveness to electrical stimulation in pediatric cochlear implant users.
- Further research with varied electrical pulse configurations is needed to explore eCAP sensitivity to PPD for estimating neural survival.
Objectives:
The aim of this study is to (1) investigate the effects of increasing the pulse phase duration (PPD) on the neural response of the electrically stimulated cochlear nerve (CN) in children with CN deficiency (CND) and (2) compare the results from the CND population to those measured in children with normal-sized CNs.
Design:
Study participants included 30 children with CND and 30 children with normal-sized CNs. All participants used a Cochlear Nucleus device in the test ear. For each subject, electrically evoked compound action potential (eCAP) input/output (I/O) functions evoked by single biphasic pulses with different PPDs were recorded at three electrode locations across the electrode array. PPD durations tested in this study included 50, 62, 75, and 88 μsec/phase. For each electrode tested for each study participant, the amount of electrical charge corresponding to the maximum comfortable level measured for the 88 μsec PPD was used as the upper limit of stimulation. The eCAP amplitude measured at the highest electrical charge level, the eCAP threshold (i.e., the lowest level that evoked an eCAP), and the slope of the eCAP I/O function were measured. Generalized linear mixed effect models with study group, electrode location, and PPD as the fixed effects and subject as the random effect were used to compare these dependent variables measured at different electrode locations and PPDs between children with CND and children with normal-sized CNs.
Results:
Children with CND had smaller eCAP amplitudes, higher eCAP thresholds, and smaller slopes of the eCAP I/O function than children with normal-sized CNs. Children with CND who had fewer electrodes with a measurable eCAP showed smaller eCAP amplitudes and flatter eCAP I/O functions than children with CND who had more electrodes with eCAPs. Increasing the PPD did not show a statistically significant effect on any of these three eCAP parameters in the two subject groups tested in this study.
Conclusions:
For the same amount of electrical charge, increasing the PPD from 50 to 88 μsec for a biphasic pulse with a 7 μsec interphase gap did not significantly affect CN responsiveness to electrical stimulation in human cochlear implant users. Further studies with different electrical pulse configurations are warranted to determine whether evaluating the eCAP sensitivity to changes in the PPD can be used as a testing paradigm to estimate neural survival of the CN for individual cochlear implant users.
