South African Journal of Science
On-line version ISSN 1996-7489
SMIT, J.E.; HANEKOM, T. and HANEKOM, J.J.. Predicting action potential characteristics of human auditory nerve fibres through modification of the Hodgkin-Huxley equations. S. Afr. j. sci. [online]. 2008, vol.104, n.7-8, pp. 284-292. ISSN 1996-7489.
In 1952, Hodgkin and Huxley published an empirical set of equations describing changes in the neural membrane potential of the squid giant axon during the application of depolarizing or hyperpolarizing stimuli. As these equations were derived for an unmyelinated nerve fibre, there are reservations about their applicability to describe action potential propagation adequately in myelinated mammalian nerve fibres. This study proposes possible modifications of the Hodgkin-Huxley equations to describe action potentials generated in the Ranvier node of a human sensory nerve fibre, as applied specifically to the prediction of temporal characteristics of the human auditory system. Simulations of the effects of these modifications were performed in Matlab. Results suggest that the temporal characteristics of the human auditory system may be predicted better by using the modified set of equations. This finding is of value in creating more realistic neural models of the electrically stimulated human auditory system. Refractory periods were similar to those of general sensory nerve fibres of the same calibre. Relative refractory periods decreased with progressive retrograde nerve fibre degeneration. Chronaxie times decreased and rheobase current values increased when retrograde nerve fibre degeneration was simulated. Rheobase currents were also greater for straight array compared with contour array stimulation. Mean latencies decreased with progressive retrograde nerve fibre degeneration and agreed well with neural response telemetry. They also decreased with an increase in stimulus intensity.