Block Phenomena During Electric Micro-Stimulation of Pyramidal Cells and Retinal Ganglion Cells

Electric micro-stimulation of the nervous system is a means to restore various body functions. The stimulus amplitude necessary to generate action potentials, the lower threshold (LT), is well characterized for many neuronal populations. However, electric overstimulation above an upper threshold (UT...

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Autores principales:	Sogand Sajedi, Andreas Fellner, Paul Werginz, Frank Rattay
Formato:	article
Lenguaje:	EN
Publicado:	Frontiers Media S.A. 2021
Materias:	pyramidal cell retinal ganglion cell axon initial segment neural stimulation computer simulation upper threshold Neurosciences. Biological psychiatry. Neuropsychiatry RC321-571
Acceso en línea:	https://doaj.org/article/ba93a0b8f51c49068de4bab4d44a70d6
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spelling	oai:doaj.org-article:ba93a0b8f51c49068de4bab4d44a70d62021-12-01T09:11:21ZBlock Phenomena During Electric Micro-Stimulation of Pyramidal Cells and Retinal Ganglion Cells1662-510210.3389/fncel.2021.771600https://doaj.org/article/ba93a0b8f51c49068de4bab4d44a70d62021-11-01T00:00:00Zhttps://www.frontiersin.org/articles/10.3389/fncel.2021.771600/fullhttps://doaj.org/toc/1662-5102Electric micro-stimulation of the nervous system is a means to restore various body functions. The stimulus amplitude necessary to generate action potentials, the lower threshold (LT), is well characterized for many neuronal populations. However, electric overstimulation above an upper threshold (UT) prevents action potential generation and therefore hinders optimal neuro-rehabilitation. Previous studies demonstrated the impact of the UT in micro-stimulation of retinal ganglion cells (RGCs). The observed phenomenon is mostly explained by (i) reversed sodium ion flow in the soma membrane, and (ii) anodal surround block that hinders spike conduction in strongly hyperpolarized regions of the axon at high stimulus intensities. However, up to now, no detailed study of the nature of these phenomena has been presented, particularly for different cell types. Here, we present computational analyses of LT and UT for layer 5 pyramidal cells (PCs) as well as alpha RGCs. Model neurons were stimulated in close vicinity to the cell body and LTs and UTs as well as the ratio UT/LT were compared. Aside from a simple point source electrode and monophasic stimuli also realistic electrode and pulse configurations were examined. The analysis showed: (i) in RGCs, the soma contributed to action potential initiation and block for small electrode distances, whereas in PCs the soma played no role in LTs or UTs. (ii) In both cell types, action potential always initiated within the axon initial segment at LT. (iii) In contrast to a complete block of spike conductance at UT that occurred in RGCs, an incomplete block of spiking appeared in PC axon collaterals. (iv) PC axon collateral arrangement influenced UTs but had small impact on LTs. (v) Population responses of RGCs change from circular regions of activation to ring-shaped patterns for increasing stimulus amplitude. A better understanding of the stimulation window that can reliably activate target neurons will benefit the future development of neuroprostheses.Sogand SajediAndreas FellnerPaul WerginzFrank RattayFrontiers Media S.A.articlepyramidal cellretinal ganglion cellaxon initial segmentneural stimulationcomputer simulationupper thresholdNeurosciences. Biological psychiatry. NeuropsychiatryRC321-571ENFrontiers in Cellular Neuroscience, Vol 15 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	pyramidal cell retinal ganglion cell axon initial segment neural stimulation computer simulation upper threshold Neurosciences. Biological psychiatry. Neuropsychiatry RC321-571
spellingShingle	pyramidal cell retinal ganglion cell axon initial segment neural stimulation computer simulation upper threshold Neurosciences. Biological psychiatry. Neuropsychiatry RC321-571 Sogand Sajedi Andreas Fellner Paul Werginz Frank Rattay Block Phenomena During Electric Micro-Stimulation of Pyramidal Cells and Retinal Ganglion Cells
description	Electric micro-stimulation of the nervous system is a means to restore various body functions. The stimulus amplitude necessary to generate action potentials, the lower threshold (LT), is well characterized for many neuronal populations. However, electric overstimulation above an upper threshold (UT) prevents action potential generation and therefore hinders optimal neuro-rehabilitation. Previous studies demonstrated the impact of the UT in micro-stimulation of retinal ganglion cells (RGCs). The observed phenomenon is mostly explained by (i) reversed sodium ion flow in the soma membrane, and (ii) anodal surround block that hinders spike conduction in strongly hyperpolarized regions of the axon at high stimulus intensities. However, up to now, no detailed study of the nature of these phenomena has been presented, particularly for different cell types. Here, we present computational analyses of LT and UT for layer 5 pyramidal cells (PCs) as well as alpha RGCs. Model neurons were stimulated in close vicinity to the cell body and LTs and UTs as well as the ratio UT/LT were compared. Aside from a simple point source electrode and monophasic stimuli also realistic electrode and pulse configurations were examined. The analysis showed: (i) in RGCs, the soma contributed to action potential initiation and block for small electrode distances, whereas in PCs the soma played no role in LTs or UTs. (ii) In both cell types, action potential always initiated within the axon initial segment at LT. (iii) In contrast to a complete block of spike conductance at UT that occurred in RGCs, an incomplete block of spiking appeared in PC axon collaterals. (iv) PC axon collateral arrangement influenced UTs but had small impact on LTs. (v) Population responses of RGCs change from circular regions of activation to ring-shaped patterns for increasing stimulus amplitude. A better understanding of the stimulation window that can reliably activate target neurons will benefit the future development of neuroprostheses.
format	article
author	Sogand Sajedi Andreas Fellner Paul Werginz Frank Rattay
author_facet	Sogand Sajedi Andreas Fellner Paul Werginz Frank Rattay
author_sort	Sogand Sajedi
title	Block Phenomena During Electric Micro-Stimulation of Pyramidal Cells and Retinal Ganglion Cells
title_short	Block Phenomena During Electric Micro-Stimulation of Pyramidal Cells and Retinal Ganglion Cells
title_full	Block Phenomena During Electric Micro-Stimulation of Pyramidal Cells and Retinal Ganglion Cells
title_fullStr	Block Phenomena During Electric Micro-Stimulation of Pyramidal Cells and Retinal Ganglion Cells
title_full_unstemmed	Block Phenomena During Electric Micro-Stimulation of Pyramidal Cells and Retinal Ganglion Cells
title_sort	block phenomena during electric micro-stimulation of pyramidal cells and retinal ganglion cells
publisher	Frontiers Media S.A.
publishDate	2021
url	https://doaj.org/article/ba93a0b8f51c49068de4bab4d44a70d6
work_keys_str_mv	AT sogandsajedi blockphenomenaduringelectricmicrostimulationofpyramidalcellsandretinalganglioncells AT andreasfellner blockphenomenaduringelectricmicrostimulationofpyramidalcellsandretinalganglioncells AT paulwerginz blockphenomenaduringelectricmicrostimulationofpyramidalcellsandretinalganglioncells AT frankrattay blockphenomenaduringelectricmicrostimulationofpyramidalcellsandretinalganglioncells
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Block Phenomena During Electric Micro-Stimulation of Pyramidal Cells and Retinal Ganglion Cells

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