I'm reading this paper that the Human Brain Project published in Cell and I'm confused how they recorded the firing rates shown in the firing below:
In the publication, they mention that they use the Petilla convention. However, upon reviewing that publication, I was unable to determine the procedure of characterising neuronal firing rates. How are they able to isolate a neuron's firing behaviour away from the network it is usually contained in? Where do they measure the outputted firing rate?
I am aware that usually to characterize a neuron in a network, Spike Sorting or single-neuron recording can be used, however this doesn't seem like a valid way to characterize the physiological properties of an individual neuron.
If you consult the experimental procedures section of the paper, you can find that they used methods previously established in three papers. However, upon reviewing these papers, it appears that the neurons were stimulated while still inside the tissue, but after the tissue had been sliced. However, this seems so absurd that I must be misreading it.
How were the electrophysiological properties of these neurons characterised?