Consideration of neurons as voltage sources allows to apply to them a concept of an output impedance. The value of the neuron's output impedance would define how much current you can draw from it until it stops to deliver it's nominal voltage. Practically, this sets requirements for tools of electrophysiology. For example - the input impedance of an amplifier. If it's too low, the recorded signals' amplitude will be altered by measurement. I guess output impedances of neuronal sources strongly differ depending on how far and what kind of source is generating the signal.
What is the output impedance of neural sources that generate an ECoG signal?
Oh my, this is a complex question. I don't work much with passively-recorded ECoG data, but rather with applied focal stimulation to brain regions of interest. In my setting, we use both constant-current and constant-voltage stimulators (depending on the project), and have some difficulty translating findings between the two because the brain imepdances can change based on medications, degree of dehydration, degree of edema/microglial activation from craniotomy, etc. There also appears to be extensive inter-personal variation in impedance. Your question is very good and I'll be interested to see what an ECoG person's response is.
Thank you for replies! If the values are strongly varying depending on particular setup settings, the most reliable way would be to measure it for every particular experiment to make the data translatable between recordings.
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