ED Sciences de la Vie et de la Santé
How does the brain integrate sensory and emotional memories? A study of the role of the hippocampus in sensory preconditioning in rats
by Mélie TALARON (Institut de neurosciences cognitives et intégratives d'Aquitaine)
The defense will take place at 14h00 - Amphithéâtre BBS Batiment Bordeaux Biologie Santé Université de Bordeaux 2 Rue Dr Hoffmann Martinot, 33000 Bordeaux
in front of the jury composed of
- Etienne COUTUREAU - Directeur de recherche - Université de Bordeaux - Directeur de these
- Joshua JOHANSEN - Professor - University of California - Rapporteur
- Valérie DOYERE - Directrice de recherche - Institut des Neurosciences Paris-Saclay - Rapporteur
- Charlotte BONARDI - Maîtresse de conférences - University of Nottingham - Examinateur
- Lisa ROUX - Directrice de recherche - Université de Bordeaux - Examinateur
- Nathan HOLMES - Associate Professor - The University of New South Wales - CoDirecteur de these
Animals and humans adapt to their environments by learning to predict motivationally significant events such as the presence of food or danger. These predictions are often based on direct experience of the contingencies between different stimuli and events (e.g., a sound followed by the attack of a predator) but can also be generated in the absence of such experience. For example, by linking the sensory and emotional elements of distinct memories, we can generate novel inferences about stimuli that have only ever been experienced as innocuous. This type of inference has implications for how memories are encoded and stored in the brain; and raises the question of how they are integrated to generate adaptive behavior. The encoding and integration of associative memories are known to be hippocampus-dependent. Yet, the differential contributions of dorsal versus ventral hippocampus and their connectivity in these processes remains unclear. This thesis combines behavioral paradigms, pharmacological inactivations, fiber photometry recordings, and chemogenetic manipulations to investigate the role of dorsal and ventral hippocampus in the encoding and integration of sensory and emotional memories in rats. In the first set of experiments, we establish auditory-visual sensory preconditioning and show that integration operates via mediated learning: rats retrieve past information at the time of conditioning to form new associations between stimuli. In a second line of work, we use pharmacological inactivation to investigate the causal role of dorsal and ventral hippocampus in the different stages of sensory preconditioning. We show that ventral, but not dorsal, hippocampus is required to form innocuous stimulus-stimulus associations, and that both subregions are necessary for mediated learning. Critically, we identify the signature of successful mediated learning by evidencing higher dorso-ventral hippocampus connectivity during stimulus presentations. We show that this connection is part of a broader network supporting mediated learning, which includes the perirhinal cortex. Finally, using chemogenetic manipulation in a gustatory sensory preconditioning protocol, we demonstrate that the hippocampus is also critical to encode and integrate memories even when stimuli are unimodal. This work highlights the differential contributions of dorsal and ventral hippocampus in animals' ability to infer outcomes in the absence of direct experience when facing novel situations.
Crossed approaches of oenology and experimental economics concerning the evaluation of products (grapes, wines) from low phytosanitary input vineyard systems
by Marie-Amélie ALAYRAC (Oenologie)
The defense will take place at 9h30 - Amphithéâtre Institut des Sciences de la Vigne et du Vin 210 chemin de Leysotte 33140 Villenave d'orion
in front of the jury composed of
- Philippe DARRIET - Professeur des universités - Université de Bordeaux - Directeur de these
- Cécile COULON-LEROY - Maîtresse de conférences - ESA Angers - Rapporteur
- Foued CHERIET - Professeur - Institut Agro Montpellier - Rapporteur
- Marie BLACKFORD - Chargée de recherche - Agroscope Changins - Examinateur
- Eric GIRAUD-HERAUD - Directeur de recherche - INRAE - Examinateur
- Yann RAINEAU - Ingénieur de recherche - INRAE - CoDirecteur de these
This PhD thesis is set within the context of the agroecological transition of viticulture and the need to reduce the use of plant protection products while maintaining wine quality and typicity. It primarily draws upon oenology and experimental economics to evaluate different strategies aimed at adapting vineyards to current sanitary and environmental challenges. The first part of the thesis focuses on the analysis of oenological impacts associated with the development of grapevine fungal diseases, namely downy mildew and black rot. Experimental vinifications incorporating increasing proportions of disease-affected grapes were carried out to produce wines that were subsequently subjected to sensory evaluation and to the identification of chemical markers reflecting the presence and severity of these fungal alterations. Analyses were performed using gas chromatography–mass spectrometry and ion chromatography, techniques that can be readily implemented in oenological laboratories. The second part concerns the characterization of grapes and wines obtained from breeding progenies resulting from crosses between Bordeaux grape varieties, Cabernet Franc and Petit Verdot, and resistant parental lines carrying resistance genes against downy mildew and powdery mildew. These genotypes were evaluated over several vintages through the study of their agronomic performance, phenological behaviour, and oenological potential. The resulting grapes and wines were subjected to physicochemical analyses and sensory evaluations conducted by expert panels in order to identify the most promising genotypes for the production of wines exhibiting characteristics compatible with the typicity of Bordeaux red and white wines. Finally, the third part investigates consumer perceptions of varietal innovation strategies aimed at reducing pesticide use in viticulture. Two experimental economics protocols combining wine tasting and incentive-compatible preference elicitation mechanisms were conducted with 267 regular Bordeaux wine consumers. The first experiment demonstrates that varietal innovation does not, in itself, constitute a barrier to consumer acceptance of wines. It also shows that information relating to the reduction of plant protection product use increases the economic valuation of wines, whereas the sole argument of varietal tradition does not. The second experiment explores the consequences of a reduction in the availability of conventional wines and reveals consumers' attachment to product diversity. The results further indicate that reducing product availability may constitute an original tool for eliciting consumer preferences and provide new insights into the observed discrepancies between willingness to pay and willingness to accept. Taken together, these studies aim to improve our understanding of the oenological, sensory, and economic consequences of strategies designed to reduce phytosanitary inputs, while supporting the development of innovative solutions that reconcile environmental sustainability, preservation of wine typicity, and consumer acceptance.
ED Sciences et environnements
Effects of endocrine disrupting compounds on the thyroid system, development and microbiota of rainbow trout
by Marine SUCHET (Environnements et Paléoenvironnements Océaniques et Continentaux)
The defense will take place at 8h30 - Amphithéâtre PABA Bâtiment B5, Allée Geoffroy Saint-Hilaire, CS 50023, 33615 Pessac
in front of the jury composed of
- Jérôme CACHOT - Professeur - Université de Bordeaux - Directeur de these
- Laure BELLEC - Maîtresse de conférences - Université de Bordeaux - CoDirecteur de these
- Xavier COUSIN - Chargé de recherche - INRAe - Rapporteur
- Emilie FARCY - Professeure - Université de Montpellier - Rapporteur
- Jean-Baptiste FINI - Professeur - Muséum National d'Histoire Naturelle - Examinateur
- Patrice GONZALEZ - Directeur de recherche - CNRS - Examinateur
- Carmen PALACIOS - Maîtresse de conférences - Université Perpignan Via Domitia - Examinateur
- Maeva GIRAUDO - Ingénieure de recherche - Sorbonne Université - Examinateur
Interest in endocrine disrupting compounds (EDCs) is growing due to their increasing use and their classification as substances of very high concern at the European level. Among them, fluoride, used in a variety of industrial processes and for the artificial fluoridation of drinking water, has been listed on the EU list II of suspected EDCs. Tebuconazole is one of the most widely used fungicides worldwide, whose EDC effects, notably on the thyroid hormone system, are well described. Aquatic environments act as a sink for these pollutants, to which fish are exposed and particularly vulnerable during early life stages. Beyond the direct effects on the host, exposure to pollutants can also exert harmful effects on the fish microbiome, whose disruption can affect their health and disease resistance. In this context, the objectives of this work were to evaluate the effects of (1) chronic fluoride exposure during early life stages of rainbow trout (RT, Oncorhynchus mykiss) on development and the thyroid hormone system; (2) chronic exposure to fluoride or tebuconazole on the bacterial microbiomes of the gills, epidermal mucus and intestine; and (3) chronic fluoride exposure on the microbiome responses of RT to a viral infection. RT embryos were exposed to a range of fluoride concentrations (1.5 to 51.5 mg/L) from 6 to 40 days post-fertilisation. The results showed significant developmental effects, including growth inhibition and increased axial skeletal malformations, as well as thyroid disruption, including upregulation of key genes of the thyroid hormone system and histopathological alterations of thyroid follicles. RT were also exposed to 6.8 or 24.7 mg/L fluoride or 51.7 µg/L tebuconazole for seven months. The results indicated tissue-specific alterations of bacterial communities across the three tissues considered, including altered bacterial diversity and interactions, as well as an increase in potentially pathogenic taxa. Finally, RT previously exposed to fluoride were subjected to infection with the infectious haematopoietic necrosis virus. The results indicated that the virus altered bacterial communities in all three tissues, and that fluoride pre-exposure modulated the microbial response to infection, altering the temporal dynamics of potentially pathogenic or beneficial taxa, while increasing host susceptibility to infection. In conclusion, these results demonstrate an EDC effect of fluoride from the earliest life stages of RT, as well as a capacity to alter the microbiome and host-microbiome interactions, suggesting interconnections between the different biological systems affected.