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Extracellular stimulation of neural tissue is done using electrode. Amount of current determines neurons how far from the electrode will be excited. How much current is required to stimulate the neuron in immediate vicinity? Such information is not available on internet.

ertyu
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    "Such information is not available on internet." - wrong, but okay, I understand it's hard to find. The problem with your question is it is ill-defined: what do you mean by immediate vicinity? That term is meaningless. It also doesn't say anything about the rest of the setup: how far apart are the electrodes, how big are they, what part of the neuron is nearby? If you really want to know the minimum current to make a neuron spike, all you need is the input resistance, resting potential, and threshold, but that's for current delivered directly across the membrane. – Bryan Krause May 26 '17 at 22:07
  • immediate vicinity means neurons in contact with the electrode. single electrode. how big? why? say 100 micron dia. axon is in contact. – ertyu May 26 '17 at 22:30
  • "If you really want to know the minimum current to make a neuron spike, all you need is the input resistance, resting potential, and threshold, but that's for current delivered directly across the membrane. " interesting.please tell me the calculation. rest potential -70mV, threshold -55mV and what is input resistance- resistance of electrode wire? let us say it is 100 Ohms or R if you would like. – ertyu May 26 '17 at 22:33
  • Because not all of the current will actually go through the membrane of the cell, especially if the ground is far away or not in the same direction. Input resistance is the input resistance of the cell. If you just want a ballpark estimate for some engineering project, typical extracellular stimulation intensities are in the microamp range, but the current you have to deliver across a membrane to make a cell spike is in the picoamp range, depending on cell type and other conditions. – Bryan Krause May 26 '17 at 22:39
  • To calculate for one cell, knowing the input resistance of the cell (not your wire), all you need is Ohm's law, knowing you want to change the voltage by, in your case, 15mV. – Bryan Krause May 26 '17 at 22:40
  • "the current you have to deliver across a membrane to make a cell spike is in the picoamp range" does this require electrode inside the neuron like the glass pipettte electrode. – ertyu May 26 '17 at 22:45
  • "To calculate for one cell, knowing the input resistance of the cell (not your wire), all you need is Ohm's law, knowing you want to change the voltage by, in your case, 15mV. " For this, are two electrodes required,one inside cell and one outside? in that case why resistance has to be known? just both electrodes should be at 15mV difference. – ertyu May 26 '17 at 22:51
  • You always have two electrodes - in your case, your ground someplace is one of them. And yeah, I'm talking about inside the neuron with an electrode of some sort. For outside, you have to consider everything else, which is basically all the other places your current could flow. Imagine a massively parallel circuit where only one of the paths actually goes across the membrane you are interested in. – Bryan Krause May 26 '17 at 23:51

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