What are the differences between the 'Input_resistance_mohm' and 'ri'?

Technical
1

Hi everyone,

I am trying to access several electrophysiological data using the Allen SDK. Currently, I am especially interested in getting the Resistance input of each mouse cell. Though I successfully access various computed electrophysiological features by using ctc.get_ephys_features(), I am faced with two columns reporting Resistance input, the first one named ‘input_resistance_mohm’, and the second one ‘ri’. When looking at the Allen Cell Types Features Glossary (Allen Cell Types Features Glossary - Google Docs) I saw no distinction between the two features, as they both represent “Input resistance”, even though the two values are different (see image)

Input_resistance_AllenSDK
Input_resistance_AllenSDK1148×401 107 KB

Can someone explain me the difference between these two values please?
I take advantage of this message to thank you for all this great database and all the features that come with it!

Best regards,
Julien

2

Thanks for the question. The values in “input_resistance_mohm” are calculated in voltage clamp mode at the beginning of the recording from a single step, and the values in “ri” are calculated in current clamp mode from a set of hyperpolarizing current steps.

3

Hi,
Thank you for your response and this clarification.
So, if I understood that correctly, “input_resistance_mohm” corresponds to the measure of the input resistance at the beginning of the recording and ‘ri’ to a latter measurement in current clamp mode, am I right?
If this is the case, in your opinion, which values should I use to study the cell’s electrophysiological properties? I would suppose the “input_resistance_mohm” as it is at the beginning of the experiment, and so when the cell is in better health, but I wouldn’t say no to an external advise.
Also, just to confirm, is ‘ri’ expressed in MOhm too?

thank you for your help,
Best,
Julien

4

I would probably use the “ri” value, actually, since it’s based on more data collected from the cell (so you get some benefits of averaging, essentially). Also, if you are interested in the firing rates vs stimulus amplitudes (as you mentioned in another post), the steps used to calculate “ri” are collected just before those, so the cells should be in similar states.

And yes, “ri” is also in megaohms.

5

Hi, Thank you very much, that’ll help!

Best,
Julien