In my current experiment, I am doing AFC using a 0.7 mA, 0.5 second footshock. 24 hours later, while some animals show high freezing in the first block of recall (1 block = 2 tones), some animals show zero to about 10% freezing, which is very low.
I have been using male Wistar rats for this experiment, 55-60 days old at the beginning of the experiment.
Because of this diversity in freezing, I want to segregate the animals into learners and non-learners. Would be great if you can suggest criteria that you have used for your experiments or guide me towards publications which have used criteria to make this distinction.
Please let me know if you need any more details!
Much thanks in advance :)
The only objective, non-arbitrary way to do that would be to compare the level of freezing within each animal between baseline (pre-tone) and during the tone. If there is no statistical difference the animal is a non-learner. However, chances are that there are not too many that pass that criterium.
An alternative approach would be to do a statistical test for bimodality. If there is a truly bimodal distribution you are done.
Lastly, you could set an arbitrary threshold and call one group non-learners.
good luck!
Thanks a lot. Nils :)
How do you think I could justify setting an arbitrary threshold? I mean, what could be a solid reason to choose one specific level of freezing as my cut off?
Dear Prabahan, if the first two approaches do not work, there really is no solid reason for doing so. Nevertheless, similar things are often done. Although this is of course not a good reason to also do it ;)
My guess is you want to separate them in two groups to subsequently analyze and compare them on some measure. If so, you could also not split them in two groups but create a scatter plot and test for the correlation between freezing and your measure of interest.
So it depends a bit on what you want to do with the results. What do you want to do with the results?
best
Nils
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