scholarly journals Investigating the Recovery Properties of Auditory Nerve Fibres at Different Cochlear Regions using Electrically Evoked Compound Action Potential

Author(s):  
Abishek Umashankar ◽  
Deepika Jayachandran

Introduction: Investigating the recovery function and refractory properties of auditory nerve is essential for us to understand the physiology at neural level, not many tools are available to carry out research in humans. Electrically Evoked Compound Action Potential (ECAP) helps us to record the action potential and also provides us with an option of varying the Interpulse Interval (IPI), hence there is a need to carry out research in Cochlear Implant (CI) users with the help of ECAP. Aim: To investigate the refractory property of the neurons and the response characteristics at different cochlear regions. Materials and Methods: Fifty CI users from age 3-10 years with a minimum hearing experience of three months underwent ECAP measures at various IPI. The data were further statistically analysed using SPSS software version 20.0, descriptive and inferential statistics were carried out using ANOVA. Results: It was found that a high ECAP threshold (648 cu) could be found at the basal region of cochlea when compared to medial (658 cu) and apical region (785 cu) at 300 μs and similar higher thresholds at different IPI, thus attributing to the fact that with increase in population of nerve fibres, a better threshold could be achieved. Another finding revealed that with very low IPI, the ECAP thresholds were elevated, with neural recruitment being a contributing factor. Conclusion: There was a difference in neural population amongst individuals, even with better auditory performance. ECAP is one of the objective tool to measure neural function and outcomes in CI individuals.

2018 ◽  
Vol 95 (4) ◽  
pp. 99-120
Author(s):  
D. S. Klyachko ◽  
◽  
A. V. Pashkov ◽  
S. V. Gadaleva ◽  
I. V. Naumova ◽  
...  

2016 ◽  
Vol 82 (2) ◽  
pp. 123-130 ◽  
Author(s):  
Fernanda Ferreira Caldas ◽  
Carolina Costa Cardoso ◽  
Monique Antunes de Souza Chelminski Barreto ◽  
Marina Santos Teixeira ◽  
Anacléia Melo da Silva Hilgenberg ◽  
...  

Author(s):  
Tim Brochier ◽  
Colette M. McKay ◽  
Robert P. Carlyon

Abstract Variations in the condition of the neural population along the length of the cochlea can degrade the spectral and temporal representation of sounds conveyed by CIs, thereby limiting speech perception. One measurement that has been proposed as an estimate of neural survival (the number of remaining functional neurons) or neural health (the health of those remaining neurons) is the effect of stimulation parameters, such as the interphase gap (IPG), on the amplitude growth function (AGF) of the electrically evoked compound action potential (ECAP). The extent to which such measures reflect neural factors, rather than non-neural factors (e.g. electrode orientation, electrode-modiolus distance, and impedance), depends crucially upon how the AGF data are analysed. However, there is currently no consensus in the literature for the correct method to interpret changes in the ECAP AGF due to changes in stimulation parameters. We present a simple theoretical model for the effect of IPG on ECAP AGFs, along with a re-analysis of both animal and human data that measured the IPG effect. Both the theoretical model and the re-analysis of the animal data suggest that the IPG effect on ECAP AGF slope (IPG slope effect), measured using either a linear or logarithmic input-output scale, does not successfully control for the effects of non-neural factors. Both the model and the data suggest that the appropriate method to estimate neural health is by measuring the IPG offset effect, defined as the dB offset between the linear portions of ECAP AGFs for two stimuli differing only in IPG.


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