I ran a novel object recognition test on mice that underwent traumatic brain injury (or sham) and were treated with a drug (or vehicle). My sham controls (both treated and untreated) performed well and showed clear preference for the novel object (>60%), the TBI untreated group exhibited no preference for the novel object. Curiously, the drug treated TBI group exhibited a pretty strong avoidance of the novel object, only actively investigating it about 25% of the time. Does anyone with experience in this task have some insight into how to interpret this result? Is it neophobia? Anxiety?
Hi, Kate! Can you provide more information:
How do you calculate novel object preference?
Did your TBI groups spend an equivalent amount of time exploring objects as the sham groups (both during object habituation and novel object probe)?
What was your NOR protocol?
Hi, Kate! Have you tested what this drug did to the animals with no TBI?
Katherine: My protocol was 30 minutes of acclimation to the chamber the day before testing. On the day of testing, mice spent 10 minutes with two identical objects, then 2 hours later were replaced in the chamber with one novel and one familiar object for 5 minutes. The discrimination index was calculated as (time with novel)/(novel + familiar) * 100. I tested 4 groups (sham/vehicle; sham/drug; TBI/vehicle; TBI/drug), the first three groups spent the same amount of time with the objects, the TBI/drug group spent a lot more time with the objects overall (with the majority of that time being with the familiar object).
Our injury paradigm directly affects superficial cortical layers but produces mild global white matter damage throughout the forebrain.
Luciano: the sham injured mice treated with the drug performed as well as the sham controls.
Hi Kate. Did you counterbalance the objects? For example, we observed a bias towards objects made of plastic and an aversion to glass, so we always try to keep the material as similar as possible (and only change one dimension-like form). During initial exploration with 2 familiar objects, do you see similar exploration of both objects? Or do you see a 'side' bias? Do the groups behave similarly during this first presentation (signs of hyperactivity, anxiety, latency to approach objects)?
I'm in agreement with Zsuzsanna's comments. I would try to rule out any potential confounds that might arise from the drug/injury combination, like locomotor or sensory deficits. For example, impaired visual acuity could result in a preference for a dark/high-contrast object. You could get around this by counterbalancing your objects, as Zsuzsanna mentioned. You might also check active exploration time vs passive proximity to the object, if your initial scoring did not take that into account.
Assuming you rule out other factors, I would be curious about novelty-suppressed feeding (otherwise known as novelty-induced hypophagia) in your mice. I like this assay in your scenario, because there is a conflict between novelty-induced anxiety (or neophobia, as you put it) and hunger. You could also try elevated plus or zero mazes, or light/dark emergence as other measures of anxiety.
Thank you for the suggestions! I did counterbalance the objects. Side bias should not be a problem as that was counterbalanced as well. Based on your advice I think it's a good idea to go back through the videos to more closely assess active vs passive exploration. I will also go back and assess the initial exploration of the two familiar objects. I just got elevated plus maze data on these mice (still to be scored) and so will take that into account as well. I appreciate you taking the time to provide some insight!
Dear Kate, if you want to take into account the initial exploration of the objects as a baseline, you can utilize the recognition index (RI), as described in:
https://www.researchgate.net/publication/259956779_Behavioral_Methods_for_the_Study_of_the_Ras-ERK_Pathway_in_Memory_Formation_and_Consolidation_Passive_Avoidance_and_Novel_Object_Recognition_Tests
If the RI confirms the result obtained with the discrimination index (DI), then you might really have found a neophobic phenotype. You said you have counterbalaced for both the objects and the sides, but the best way to check for possible biases is to compare the RI and the DI. If you still find a significant aversion for the new object, then it would be interesting to investigate this phenotype with a different test. As Katherine suggested, you could use the novelty-suppressed feeding test, by which you can evaluate the hyponeophagia phenomenon (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3197427/).
Article Behavioral Methods for the Study of the Ras–ERK Pathway in M...
Thank you Raffaele, I have not come across this method of scoring NOR before, I will definitely be checking this!
I wonder if this drug challenge revealed a TBI-induced autisitc-like behavior.
That's an interesting idea Luciano, I will look into it. I hope you are doing well!
Dear Kate
Wishing I can help but it is not in my interesting
Regards
Hi Kate. Though it is very late, I'm making analysis of NOR on C57BL/6 mice comparing cognitive function in mature adults x aged adults. I would expect the best recognition indexes on younger mice, but as far as I'm analyzing the videos until the moment, for a period of 3 min, there is a strong preference for the familiar object on mature adults. I still do not have data for old mice, but even without those results, the strong preference for familiar object did scare me. I have found this reference and it fits with my results, since I'm using female C57. As they say, C57 females are very bad on this task when compared with males.
Article Sex Differences in the Behavioral Response to Spatial and Ob...
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials Chemistry
- Polymer Chemistry