We have been doing novel object recognition tests on rats during our day (morning and afternoon), which is their night. I've read that mice perform better during the night under a red light (their day time) with less mistakes. I was wondering if anyone has done any similar behavioural (memory/learning) tests on rats during the night, and if the results differed from the day.
A lot of behavioural experiments tend to be done on mice/rats that are on reverse light-dark cycle in which the rooms were lighted for 12 hours (usually smth like 6pm-6am) and in the dark of 12 hours (6am-6pm), which means experiments where carried out out during night. For my previous lab, I do know that addiction/IVSA stuff were done in the dark cycle and it mattered a lot. I was doing Morris Water Maze, and did find that animals performed differently in the morning than afternoon (they performed better in the morning). So yeah, i guess overall the answer is yes, it matters.
We utilize both rats and mice in our lab. Rats were on a reverse light-dark cycle and perform far better, in my opinion, on behavioral tests (conditioned place preference, novel object, T maze, radial arm maze, etc.). Our mice were initially on a normal light-dark cycle, which was opposite of the rats. While they did perform as needed, it was apparent that the mice were groggy and less active during certain behavioral tasks. After we matched the L-D cycle to the rats (8pm on, 8am off), the mice seemed to perform better and were noticeably more active. This was all conducted under red lighting as well.
It makes sense to assume that rodents will be more active during their night cycle, but if you have resources stating otherwise I'd really like to read them. It is also important to note what behavioral paradigm you are using. If your paradigm requires heavy use of extra-maze cues, running them in full illumination may yield different results compared to red illumination. Likewise, their attentiveness may differ if the mice are tired vs. fully awake. This may depend on how far into their light or dark cycle you begin testing.
Thanks Jacob and Shawn! We're only doing the novel object recognition tests on our rats. We've noticed during the tests that were done in the morning, they tend to be not very active and sit back. Unfortunately the light cycle (lights on from 8am-8pm) cannot be adjusted as they're housed with rats from other labs. But I could run the tests after 8pm since the cycle seem to have some effects on the tests.
I was wondering if you had experiences with running any of the tests under red light, and how that would affect the recording of the test (we would like to video record the experiment, but I'm doubtful that the camcorder could pick up the rat movements clearly since it's pretty dark with just red lights on). In this case, would manual recording be the only viable method?
That is a bit of an issue. As you suggested, try running after the light cycle and see if you get any changes in activity. One big factor to consider is how close to the L-D switch you are testing animals. For example, rats/mice will be more groggy and less active if you test them first thing after the dark cycle starts. Waiting an hour or tow post-dark cycle should improve their activity. Same concept applies to testing animals right before the light cycle starts, although the effects may be less obvious here.
We run almost all of our behavioral analyses under red illumination. We use ANYmaze tracking for open field, novel object, etc. (manually recording for NO though, to distinguish interaction from sitting on an object). Placement of lighting is determined by 1) the strain (i.e. color) of rat/mouse, 2) the tracking system you are using, and 3) the color of your table. We use a light gray table to track our C57 mice (black) at full body. The same table is used for tracking our hooded long evans, but we only track the head (black) since it contrasts with the table color. We use 2 red bulbs facing upward, toward the ceiling. This will eliminate shadows and most glares that will throw the tracking system off. Also note, this is the method that works best for our tracking system, and may differ with the software and camera quality.
well , actually in our lab we do behavioral test only in day , so i don't know if really there is difference in performance between day and night . I would like to help you more , but this is all what i have . Sorry !
How do you manage to work in the red light without bothering you?
In my lab, we always stick to the time at which the experiments are done. I have seen some very significant changes in their skilled motor behavior depending on the time data being collected.
I was wondering if any of you have any citations that show that a reversed day-night cycle is preferred when conducting behavioural experiments? I am doing a texture discrimination task (daily for a few weeks).
Dear Tanika Bawa , with a regular a day-night cycle, mice tested in behavioural experiments will be more active in the afternoon than in the morning, as they will be more active in the evening than in the afternoon. If you use a reversed day-night cycle, you will obtain higher levels of activity also in the morning. In any case, the most important point is that you perform the test always at the same time of the day. Otherwise you will have an uncontrolled variability due to circadian effects that will interfere with your behavioural outcome.
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