Effects of chronic stress on memory systems and neurogenesis in Japanese quail : influence of emotionality

Chez les mammifères, le stress chronique altère le fonctionnement de la mémoire spatiale. Cet effet délétère serait en partie dû à une inhibition de la neurogenèse hippocampique. Par ailleurs, les effets du stress seraient plus marqués chez des individus émotifs. L’objectif de cette thèse a été de tester l’ensemble de ces hypothèses chez un oiseau, la caille japonaise. Nos résultats montrent que le stress chronique altère bien spécifiquement la neurogenèse hippocampique et la mémoire spatiale chez la caille. Néanmoins, ces effets ne sont pas modulés par le niveau d’émotivité des oiseaux. En revanche, l’émotivité régulerait les interactions entre les systèmes de mémoire spatiale et indicée. Alors que chez les individus peu émotifs, les systèmes seraient relativement indépendants, ils seraient en interaction chez les individus très émotifs. Les effets du stress chronique sur la mémoire spatiale auraient donc aussi des répercussions sur la mémoire indicée chez les individus très émotifs.In mammals, chronic stress alters spatial memory functioning and it could be partly due to an inhibition of hippocampal neurogenesis. In addition, chronic stress would be more deleterious in individuals with a high emotionality trait. The objective of the thesis was to test these hypotheses in the Japanese quail. Our results show that chronic stress specifically alters hippocampal neurogenesis and spatial memory in quail. Nevertheless, these effects are not modulated by the emotionality trait of birds. On the other hand, emotionality regulate interactions between systems of spatial and cued memories. Whereas in birds with a low emotionality trait, these systems would be relatively independent, they would interact in birds with a high emotionality trait. Therefore, the effects of chronic stress on spatial memory would also affect cued memory in individuals with a high emotionality trait

Relations entre émotivité et stratégies de mémoire spatiale chez la caille japonaise

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Horses prefer to solicit a person who previously observed a food-hiding process to access this food: A possible indication of attentional state attribution

Inferring what others witnessed provides important benefits in social contexts, but evidence remains scarce in nonhuman animals. We investigated this ability in domestic horses by testing whether they could discriminate between two experimenters who differed in what they previously witnessed and decide whom to solicit when confronted with an unreachable food source based on that information. First, horses saw food being hidden in a closed bucket (impossible for them to open) in the presence of two experimenters who behaved identically but differed in their attention to the baiting process (the “witness” experimenter faced the bucket, the “non-witness” faced away). Horses were then let free with both experimenters, and their interest towards each (gaze and touch) was measured. They gazed at and touched the witness significantly more than the non-witness (n = 15, gaze: p = 0.004; touch: p = 0.003). These results might suggest that horses inferred the attentional state of the experimenters during the baiting process and used this information to adapt their later behavior. Although further study would be necessary to conclude, our study provides new insight into attentional state attribution in horses and might hint to the existence of precursors of a Theory of Mind in horses

A trait for a high emotionality favors spatial memory to the detriment of cue-based memory in Japanese quail

International audienceRecent studies provided evidence that a personality trait such as a trait for a high or a low emotionality can either promotes or impairs learning and memory performances. This variability can be partly explained because this trait may have opposite effect on memory performances depending on the memory system involved. The present study investigated in Japanese quail the relationships between emotionality and two forms of memory, spatial-memory and cue-based memory. We showed that birds with a high emotionality trait (E+), compared with birds with a low emotionality trait (E-), reached slowly but more accurately the spatial location of a rewarded cup in an arena that contains 8 identical cups. Then a second cohort of E + and E-quails was trained to solve a dual spatial/cued task in which they could use either their spatial or cue-based memory. Whereas E + birds predominantly solved the task using their spatial memory, E-birds preferentially used their cue-based memory. These findings demonstrate that a trait for a high emotionality, can influence spatial memory performances but also contributes to favor the selection of this form of memory

Role of the hippocampus in spatial memory in Japanese quail

International audienceThe Japanese quail is a powerful model to characterize behavioral, physiological, and neurobiological processes in Galliformes. Behavioral tests have already been adapted for quail to assess memory systems, but despite the pivotal role of the hippocampus in this cognitive process, its involvement in spatial memory has not been demonstrated in this species. In this study, lesions were created in the hippocampus of Japanese quail, and both lesioned and control quail were tested for spatial and cue-based learning performances. These hippocampal lesions specifically impacted spatial learning performance, but spared learning performance when birds could solve the task using their cue-based memory. These findings, thus, highlight that the hippocampus plays a crucial role and is essential for spatial declarative memory. Future studies could aim to elucidate the cellular or molecular mechanisms involved in this form of memory

Social motivation and the use of distal, but not local, featural cues are related to ranging behavior in free-range chickens (Gallus gallus domesticus)

International audienceAnimals can navigate an environment relying on different sources of information, such as geometrical or featural cues. The favoring of one type of information over another depends on multiple factors, such as inter-individual differences in behavior and cognition. Free-range chickens present different range use patterns, which may be explained by behavioral and cognitive differences. However, how behavior, cognition, and range use intercorrelate is still poorly understood. In this work, we aimed to further understand possible differences in behavior and cognition between two groups of free-range broiler chickens: those who frequently explore their range ('high rangers') and those who prefer to stay in or near the barn ('low rangers'). Prior to range access, individual behavior was measured in open field-, emergence-, and social motivation tests. To investigate cognitive differences, we analyzed whether exploratory behavior was linked to different performances in the use of distal and local spatial cues during an orientation task. During the social motivation test, low rangers showed a higher inclination to be near conspecifics than did high rangers. Our orientation tests show that chickens preferred to orientate themselves using the local cues over the distal cues. Individual differences were only found for distal, but not for local, cue use suggesting that demanding tasks are more efficient in revealing individual cognitive differences. Our results suggest that considering variation in social motivation may allow a more comprehensive understanding of chicken range use. Our results also support the importance of incorporating multiple aspects of individual differences to understand individual reactions to its environment

Le Stress maternel prénatal module le développement des capacités cognitives chez la caille japonaise

National audienceLe développement comportemental d’un individu est fortement modulé par des facteurs d’influence maternelle prénatale. Ainsi, l’exposition d’une femelle gestante ou pondeuse à des évènements stressants affecte, via des modulations de l’environnement fœtal ou du contenu hormonal des œufs, la réactivité émotionnelle et les compétences sociales des descendants. Chez les mammifères, le stress maternel prénatal module également les capacités d’apprentissage des jeunes mais chez l’oiseau, de tels effets ont rarement été explorés. Ce travail vise donc à analyser, chez la caille japonaise, les effets d’un stress maternel prénatal sur la réactivité émotionnelle et les capacités d’apprentissage et de mémorisation des jeunes femelles de 1ère génération (F1-NS, F1-S). Ainsi, des femelles pondeuses (F0) ont soit été maintenues en conditions standards (Non Stressées, nF0-NS= 16), soit été exposées à une procédure de stress chronique de 24 jours (Stressées, nF0-S= 16). Cette procédure de stress maternel a affecté la réactivité émotionnelle des jeunes puisque les femelles F1-S apparaissent plus émotives que les femelles F1-NS. De plus, dans un test d’apprentissage spatial où les oiseaux devaient apprendre à retrouver parmi 8 pots celui contenant une récompense alimentaire (pot cible), les femelles F1-S et F1-NS ne présentent pas les mêmes performances. Lors de la phase de rétention notamment, les femelles F1-S mettent plus de temps à retrouver le pot cible que les femelles F1-NS. Enfin, lors d’un test de préférence de place conditionnée où les oiseaux devaient apprendre à associer un compartiment à une récompense alimentaire, les femelles F1-S, contrairement au femelles F1-NS, ne développent pas de préférence pour cette zone renforcée. Ainsi, nos résultats montrent que les réponses émotionnelles et les capacités d’apprentissage des oiseaux peuvent être influencées par un stress maternel prénatal. De tels effets pourraient alors affecter les capacités d’adaptation et le bien-être des individus notamment en milieu d’élevage

Impact neurobiologique et comportemental du stress prénatal chez la caille japonaise (Coturnix coturnix japonica)

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Relationship between ranging behavior and spatial memory of free-range chickens

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Training level reveals a dynamic dialogue between stress and memory systems in birds

International audienceChronic stress profoundly affects forms of declarative memory, such as spatial memory, while it may spare nondeclarative memory, such as cue-based memory. It is known, however, that the effects of chronic stress on memory systems may vary according to the level of training of an individual was submitted. Here, we investigated, in birds, how chronic stress impact spatial and cue-based memories according to training level. For that, control and chronically stressed Japanese quail were trained in a task that could be solved using spatial and cuebased memory and tested for their memory performance after 5 and 15 training days (initial training and overtraining, respectively) and following an emotional challenge (exposure to an open field). Our results showed that, compared to control quail, chronic stress impacted negatively spatial memory performances in stressed birds after initial training, but these differences were lowered after overtraining. Control birds seemed to shift from spatial to cue-based memory to solve the task across overtraining. However, an emotional challenge before testing reinstated the negative impact of chronic stress on spatial memory performances between the groups, revealing that chronic stress/overtraining did not eliminate the spatial memory and differences caused by stressors can reemerge depending on the individual?s immediate psychological state. Contrary to spatial memory, cue-based memory was not affected in chronically stressed birds compared to control birds in any test occasion, confirming its resistance against the negative effects of chronic stress. Altogether these findings reveal a dynamic dialogue between stress, training level, and memory systems in birds