# Long-term impact of a semi-naturalistic living environment on rodent anxiety and cognitive abilities

I Guggenbuhl, M Berrakmouch, M Thévenet, B Messaoudi, D Gervasoni, N

Ravel, P Litaudon

► To cite this version:

I Guggenbuhl, M Berrakmouch, M Thévenet, B Messaoudi, D Gervasoni, et al.. Long-term impact of a semi-naturalistic living environment on rodent anxiety and cognitive abilities. 1st Foraging Conference, Dec 2024, Lyon, France. hal-05233455

HAL Id: hal-05233455

https://hal.science/hal-05233455v1

Submitted on 1 Sep 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
<figure><img src="image_2.png" /></figure>

# Long-term impact of a semi-naturalistic living environment on rodent anxiety and cognitive abilities

I. Guggenbuhl¹, M. Berrakmouch¹, M. Thévenet¹, B. Messaoudi¹, D. Gervasoni¹, N. Ravel¹, P. Litaudon¹

¹CNRS UMR5292-INSERM U1028-Université Lyon 1, Centre de Recherche en Neurosciences de Lyon, Bron, France

<figure><img src="image_3.png" /></figure>

<figure><img src="image_4.png" /></figure>

## Introduction

The physical and social environment have been known for a long time to influence brain function. Preclinical neuroscience studies are almost exclusively done in rodents raised in standard laboratory conditions with reduced living space, limited social interactions, impoverished environment, and unlimited food access. This sedentary lifestyle induces metabolism disorders often associated with cognitive deficits. The need for a more naturalistic approach has emerged in the field of cognitive neuroscience but requires a housing environment that allows animals to express most of their behavioral repertoire. According to this novel perspective, rather than trying to reduce inter-individual variability by standardizing housing conditions, it is essential to identify and understand the source of this individual variation and how it affects experimental outcomes. As a first step toward this goal, we evaluated the impact of a more naturalistic living environment compared to standard living conditions on behavioral performance and anxiety level. The study was first performed on a group of males and then replicated on females.

## Methods

### Housing

<figure><img src="image_5.png" /><figcaption>Conventionnal environment
(10 cages of two rats)</figcaption></figure>

* Spatially restricted environment

* A single non-selected congener

* Unlimited food access

<figure><img src="image_6.png" /><figcaption>Semi-naturalistic environment (SNE)
(10 animals in the same arena)</figcaption></figure>

* Spatially vast and diversified environment (elevated point, out of sight)

* Various and selected social interactions with 10 congeners

* Active search for food

### Protocole

<figure><img src="image_7.png" /></figure>

### Behavioral tasks

<figure><img src="image_8.png" /><figcaption>Elevated zero
maze</figcaption></figure>

(Female and male)

Assessment of anxiety
levels

The less rat is anxious, the most it spent time during 5 minutes in open arms.

<figure><img src="image_9.png" /><figcaption>Difficult version of
Morris water maze</figcaption></figure>

Spatial memory and
navigation strategy

The rats have to learn a trajectory to a submerged platform using distal clues.

<figure><img src="image_10.png" /><figcaption>Terrestrial version of
double H maze</figcaption></figure>

(Female only)

Spatial memory and
navigation strategy

The rats have to learn a trajectory to a reward in one of the arms, using distal clues. By changing the starting point of the rat, we can find out the navigation strategy used by the rat.

<figure><img src="image_11.png" /><figcaption>Object
recognition task</figcaption></figure>

Working
memory

This test is based on the natural tendency for a rat to explore a more novel object than a known one. It tests both the memory of a previously explored object and the discrimination of a novel object from it. Two versions of this test have been performed: an easy and a difficult one with different or similar objects respectively

## Data analysis

For some of the experiments, rat trajectories were extracted using **DeepLabCut** software (http://www.mackenziemathislab.org/deeplabcut-home; Mathis et al., Nat. Neurosci., 2018, 21:1281-1289). From trajectories, exploration time around object, time in different zero-maze arms, time to reach reward and time spent in each water-maze quadrant were extracted using **A2V_ANA** software (Marc Thévenet).

## Results

<figure><img src="image_12.png" /><figcaption>Anxiety levels</figcaption></figure>

* SN animals are significantly less anxious than conventional ones.

* Among SN rats, females are significantly less anxious than males

<figure><img src="image_13.png" /><figcaption>Novel object recognition test
(Male only)</figcaption></figure>

<figure><img src="image_14.png" /></figure>

When the object were different (easy task) both groups of female rats exhibited good performance. They decreased their exploration of the familiar object (Obj A) during test phase indicating that this object was recognized. They showed a larger exploration of the novel object (Obj B) indicating that the two objects were discriminated. By contrast, if both groups of rats recognized the familiar object (Obj C) during the difficult version of the task, they failed to discriminate the new object (Obj D). The main difference between the two groups was the exploration strategy. Indeed, SN rats decreased their exploration after the first minute during the encoding phase whereas C rats exhibited a constant exploration during the ten minutes.

<figure><img src="image_15.png" /><figcaption>Terrestrial version of double H maze</figcaption></figure>

<figure><img src="image_16.png" /></figure>

* Faster acquisition in the initial phase for SN rats

* Maintains performance even after two days' interruption in SN rats, unlike C

<figure><img src="image_17.png" /></figure>

* No significant difference was observed between both groups during probe tests

* Probe test 1: the majority of animals from both groups choose the N arm instead of the correct one (NE), using an egocentric strategy.

* Probe test 2: the majority of animals from both groups choose the correct arm using an allocentric strategy.

<figure><img src="image_18.png" /><figcaption>Morris water maze</figcaption></figure>

* First learning phase (L1): significant difference between the two groups of males, with most SN males finding the platform by the second trial.

* No difference in females, but the C females performed better than the C male rats.

* Second learning phase (L2): No difference (group or sex) during the second learning phase.

* Probe test 1 and 2: target quadrant was more explored.

* Probe test 1: spatial memory resolution was slightly less accurate in females.

## Conclusion

These first data confirm the impact of living environment on rats cognitive performances :

* Rats raised in the SN environment clearly exhibit a diminution of anxiety level;

* Object recognition test revealed that these animals are more efficient in their object exploration during encoding;

* In the initial phase of spatial learning tasks, SN rats were faster to localize the reward arm (double H maze) or the platform (MWM). Moreover, they also consolidate more rapidly the acquired information. Taking into account the difference observed on memory consolidation in the SN group, we found it important to study more precisely the architecture of sleep in these animals.

The data presented so far are the results of group analysis. By allowing each animal to express its individuality, semi-naturalistic housing gives us the opportunity to characterize it (social interactions, physiological parameters, appropriation of space and navigation) and to link this to the behavioral results of each individual.