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Development of a purely conductance-based stochastic population auditory nerve fibre model for application in user-specific cochlear volume conduction models
Thesis (PhD (Electronic Engineering))--University of Pretoria, 2017.
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| Format: | Thesis |
| Language: | English |
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2026
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| _version_ | 1867613605519687680 |
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| access_status_str | Open Access |
| author2 | Hanekom, T. |
| author_browse | Hanekom, T. |
| author_facet | Hanekom, T. |
| collection | Thesis |
| description | Thesis (PhD (Electronic Engineering))--University of Pretoria, 2017. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/110112 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:38:48.199Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/110112 Development of a purely conductance-based stochastic population auditory nerve fibre model for application in user-specific cochlear volume conduction models Hanekom, T. werner.badenhorst@up.ac.za Hanekom, J.J. Badenhorst, Werner Auditory nerve fibre Compound model Temporal modelling Fibre population model Thesis (PhD (Electronic Engineering))--University of Pretoria, 2017. Cochlear implants (CI) provide profoundly deaf persons with a measure of speech perception through direct electrical stimulation of the surviving auditory nerve fibres (ANFs) via an array of electrodes implanted inside the cochlea. Numerous ANF and finite element volume conduction (VC) models have been developed to understand and model the resulting electrically stimulated neural response (ESNR) of the ANFs better. The stochastic nature of the ANFs directly affects the temporal nature of the ESNR, which in turn affects the speech perception of the CI user. Because of the large variance in speech perception among CI users, user-specific models that include a stochastic ANF model are required to help explain this variance and to optimise the speech perception of individual CI users. Although phenomenological ANF models exist that describe the stochastic phenomena, a physiological, conductance-based ANF model that explains and inherently models the phenomena is required to model specific CI users. This thesis describes the development of a purely conductance-based stochastic population ANF model for application in user-specific cochlear VC models. The developed model is based on the current noise method as applied to the Hodgkin-Huxley neural model, which adds a Gaussian noise current to the active compartment ionic currents. The subsequent system of stochastic differential equations (SDEs) is solved using the implicit EulerMaruyama (EM) SDE numerical method, which is graphically and analytically evaluated with respect to convergence errors and computational time against MATLAB’s ordinary differential equation solvers and the explicit EM method. The stochastic ANF model is completed through the development of a voltage-dependent current noise algorithm that maintains a low computational cost and ease of implementation compared to Markovian and other conductance-based stochastic models. Modelled results of feline ANFs show the algorithm’s adherence to in vivo stochastic fibre characteristics such as (i) a negative linear relationship between the logarithm of the relative spread of the discharge probability and the logarithm of the fibre diameter, (ii) an exponential relationship between the membrane noise and transmembrane voltage, and (iii) a decrease in latency with an increase in stimulus intensity. Further evaluation and validation of the proposed stochastic model is presented through application to a human ANF model in user-specific VC models. Different stimulus pulse rates, lengths and intensities are used to validate temporal characteristics through userspecific (i) discharge rate, latency and latency standard deviation vs stimulus intensity plots, (ii) period histograms and (iii) inter-spike interval histograms. A method for constructing user-specific ANF population models for application in their user-specific VC models is developed such that the fibre density and diameter distributions represent morphological measurements. The stochastic ANF and population models are then used to develop and analyse a method for obtaining and extracting electrically evoked compound action potentials (eCAPs) and amplitude growth functions. Although the stochastic ANF model shows little difference compared to the deterministic model when simulating eCAPs, replacing equidistant single or uniformly distributed fibres with a morphological fibre density distribution does affect the modelled eCAPs. The proposed purely conductance-based stochastic ANF model is thus capable of and essential in modelling temporal ANF characteristics, while an eCAP can be modelled faster and more accurately using a deterministic population ANF model having a morphologically based fibre density distribution. Electrical, Electronic and Computer Engineering PhD (Electronic Engineering) 2026-05-15T17:26:20Z 2026-05-15T17:26:20Z 17/11/21 2017 Thesis http://hdl.handle.net/2263/110112 en application/pdf |
| spellingShingle | Auditory nerve fibre Compound model Temporal modelling Fibre population model Development of a purely conductance-based stochastic population auditory nerve fibre model for application in user-specific cochlear volume conduction models |
| title | Development of a purely conductance-based stochastic population auditory nerve fibre model for application in user-specific cochlear volume conduction models |
| title_full | Development of a purely conductance-based stochastic population auditory nerve fibre model for application in user-specific cochlear volume conduction models |
| title_fullStr | Development of a purely conductance-based stochastic population auditory nerve fibre model for application in user-specific cochlear volume conduction models |
| title_full_unstemmed | Development of a purely conductance-based stochastic population auditory nerve fibre model for application in user-specific cochlear volume conduction models |
| title_short | Development of a purely conductance-based stochastic population auditory nerve fibre model for application in user-specific cochlear volume conduction models |
| title_sort | development of a purely conductance based stochastic population auditory nerve fibre model for application in user specific cochlear volume conduction models |
| topic | Auditory nerve fibre Compound model Temporal modelling Fibre population model |
| url | http://hdl.handle.net/2263/110112 |