Les fourmis forment des sociétés complexes où les individus sont spécialisés dans des tâches spécifiques (e.g., reproduction, soin au couvain, fourragement) et leur comportement naturel repose principalement sur l’olfaction. L’objet de ce travail était d’améliorer nos connaissances sur la division du travail, l’apprentissage et la mémoire olfactifs chez la fourmi Camponotus aethiops, qui fourrage en partie des nectars extra-floraux. Nous avons montré que la sensibilité au sucre différait entre les castes reproductrices et ouvrières, illustrant le modèle des seuils de réponse, qui postule que la division du travail émerge des différences dans la sensibilité à des stimuli biologiquement pertinents pour la réalisation des tâches. La sensibilité au sucre sous-tend les performances d’apprentissage olfactif appétitif : plus la fourmi est sensible au sucre, mieux elle apprend l’association appétitive. Ainsi, les fourrageuses, plus sensibles au sucre que les nourrices, apprenaient mieux l’association odeur-sucre. Les dimensions chimiques des odeurs (e.g. longueur de chaîne carbonée, groupe fonctionnel) et l’expérience olfactive jouent un rôle central dans la perception des odeurs. La similarité perceptuelle entre des odeurs d’un même groupe fonctionnel (aldéhyde) était inversement proportionnelle à la différence de chaîne carbonée entre les odeurs. De plus, la discrimination olfactive était améliorée par un apprentissage différentiel. Enfin, nous avons montré que la perception des mélanges d’odeurs dépendait de la combinaison du groupe fonctionnel et de la longueur de chaîne carbonée, avec généralement une plus grande saillance des alcools sur les aldéhydes et des chaînes longues sur les courtes. Notre étude apporte une meilleure compréhension de la division du travail, la perception et l’apprentissage olfactifs chez la fourmi. / Ants in compex societies where different individuals are specialized in particular tasks. In their natural environnement, the majority of ants species rely on olfactory cues. We aimed at understanding division of labour, olfactory perception and learning in the ant C. aetiops. The species forages partly on extra-floral nectaries, therefore uncovering the mechanisms underlying olfactory learning and perception of floral volatiles, is biologically relevant. We reveal interindividual variability in sucrose responsiveness among reproductive and behavioural castes, arguing in favour of models positing that division of labour emerges from differences in sensitivity to task-related stimuli. Sucrose mediates olfactory appetive learning success : the more sensitive to sucrose is an ant, the better it learns the appetive association. Accordingly, foragers, more sensitive to sucrose than nurses, learned better the odour-sucrose association. We show that odour's chemical dimensions (carton-chain lenght ; functional group) and olfactury experience play a significant role in olfactury perception in this ant species. Perceptual similarity between odours belonging to the same functional group was inversely related to the difference in carbon-chain lenght between odours and could be affected by the conditioning procedure. Finally, we demonstrated that binary mixtureperception relies on the combination of functional group and carbon-chain lenght, with generally a larger salience for alcohol over aldehydes and of long carbon-chain lenght over shorter ones. Our study contributes to a better understanding of division of labour, olfactory perception and olfactory learning in ants.

Les fourmis forment des sociétés complexes où les individus sont spécialisés dans des tâches spécifiques (e.g., reproduction, soin au couvain, fourragement) et leur comportement naturel repose principalement sur l’olfaction. L’objet de ce travail était d’améliorer nos connaissances sur la division du travail, l’apprentissage et la mémoire olfactifs chez la fourmi Camponotus aethiops, qui fourrage en partie des nectars extra-floraux. Nous avons montré que la sensibilité au sucre différait entre les castes reproductrices et ouvrières, illustrant le modèle des seuils de réponse, qui postule que la division du travail émerge des différences dans la sensibilité à des stimuli biologiquement pertinents pour la réalisation des tâches. La sensibilité au sucre sous-tend les performances d’apprentissage olfactif appétitif : plus la fourmi est sensible au sucre, mieux elle apprend l’association appétitive. Ainsi, les fourrageuses, plus sensibles au sucre que les nourrices, apprenaient mieux l’association odeur-sucre. Les dimensions chimiques des odeurs (e.g. longueur de chaîne carbonée, groupe fonctionnel) et l’expérience olfactive jouent un rôle central dans la perception des odeurs. La similarité perceptuelle entre des odeurs d’un même groupe fonctionnel (aldéhyde) était inversement proportionnelle à la différence de chaîne carbonée entre les odeurs. De plus, la discrimination olfactive était améliorée par un apprentissage différentiel. Enfin, nous avons montré que la perception des mélanges d’odeurs dépendait de la combinaison du groupe fonctionnel et de la longueur de chaîne carbonée, avec généralement une plus grande saillance des alcools sur les aldéhydes et des chaînes longues sur les courtes. Notre étude apporte une meilleure compréhension de la division du travail, la perception et l’apprentissage olfactifs chez la fourmi. / Ants in compex societies where different individuals are specialized in particular tasks. In their natural environnement, the majority of ants species rely on olfactory cues. We aimed at understanding division of labour, olfactory perception and learning in the ant C. aetiops. The species forages partly on extra-floral nectaries, therefore uncovering the mechanisms underlying olfactory learning and perception of floral volatiles, is biologically relevant. We reveal interindividual variability in sucrose responsiveness among reproductive and behavioural castes, arguing in favour of models positing that division of labour emerges from differences in sensitivity to task-related stimuli. Sucrose mediates olfactory appetive learning success : the more sensitive to sucrose is an ant, the better it learns the appetive association. Accordingly, foragers, more sensitive to sucrose than nurses, learned better the odour-sucrose association. We show that odour's chemical dimensions (carton-chain lenght ; functional group) and olfactury experience play a significant role in olfactury perception in this ant species. Perceptual similarity between odours belonging to the same functional group was inversely related to the difference in carbon-chain lenght between odours and could be affected by the conditioning procedure. Finally, we demonstrated that binary mixtureperception relies on the combination of functional group and carbon-chain lenght, with generally a larger salience for alcohol over aldehydes and of long carbon-chain lenght over shorter ones. Our study contributes to a better understanding of division of labour, olfactory perception and olfactory learning in ants.

Les fourmis forment des sociétés complexes où les individus sont spécialisés dans des tâches spécifiques (e.g., reproduction, soin au couvain, fourragement) et leur comportement naturel repose principalement sur l’olfaction. L’objet de ce travail était d’améliorer nos connaissances sur la division du travail, l’apprentissage et la mémoire olfactifs chez la fourmi Camponotus aethiops, qui fourrage en partie des nectars extra-floraux. Nous avons montré que la sensibilité au sucre différait entre les castes reproductrices et ouvrières, illustrant le modèle des seuils de réponse, qui postule que la division du travail émerge des différences dans la sensibilité à des stimuli biologiquement pertinents pour la réalisation des tâches. La sensibilité au sucre sous-tend les performances d’apprentissage olfactif appétitif : plus la fourmi est sensible au sucre, mieux elle apprend l’association appétitive. Ainsi, les fourrageuses, plus sensibles au sucre que les nourrices, apprenaient mieux l’association odeur-sucre. Les dimensions chimiques des odeurs (e.g. longueur de chaîne carbonée, groupe fonctionnel) et l’expérience olfactive jouent un rôle central dans la perception des odeurs. La similarité perceptuelle entre des odeurs d’un même groupe fonctionnel (aldéhyde) était inversement proportionnelle à la différence de chaîne carbonée entre les odeurs. De plus, la discrimination olfactive était améliorée par un apprentissage différentiel. Enfin, nous avons montré que la perception des mélanges d’odeurs dépendait de la combinaison du groupe fonctionnel et de la longueur de chaîne carbonée, avec généralement une plus grande saillance des alcools sur les aldéhydes et des chaînes longues sur les courtes. Notre étude apporte une meilleure compréhension de la division du travail, la perception et l’apprentissage olfactifs chez la fourmi. / Ants in compex societies where different individuals are specialized in particular tasks. In their natural environnement, the majority of ants species rely on olfactory cues. We aimed at understanding division of labour, olfactory perception and learning in the ant C. aetiops. The species forages partly on extra-floral nectaries, therefore uncovering the mechanisms underlying olfactory learning and perception of floral volatiles, is biologically relevant. We reveal interindividual variability in sucrose responsiveness among reproductive and behavioural castes, arguing in favour of models positing that division of labour emerges from differences in sensitivity to task-related stimuli. Sucrose mediates olfactory appetive learning success : the more sensitive to sucrose is an ant, the better it learns the appetive association. Accordingly, foragers, more sensitive to sucrose than nurses, learned better the odour-sucrose association. We show that odour's chemical dimensions (carton-chain lenght ; functional group) and olfactury experience play a significant role in olfactury perception in this ant species. Perceptual similarity between odours belonging to the same functional group was inversely related to the difference in carbon-chain lenght between odours and could be affected by the conditioning procedure. Finally, we demonstrated that binary mixtureperception relies on the combination of functional group and carbon-chain lenght, with generally a larger salience for alcohol over aldehydes and of long carbon-chain lenght over shorter ones. Our study contributes to a better understanding of division of labour, olfactory perception and olfactory learning in ants.

Thesis advisor: Gorica D. Petrovich / Environmental cues that are neutral in respect to hunger and feeding can come to predict food through Pavlovian appetitive conditioning. These learned cues can drive food seeking and eating independent of physiological hunger leading to overeating and obesity. However, the food outcome, and thus the value of the cues, can change due to environmental alterations. A change in the values of learned cues requires altering behavioral responses to accurately reflect the cue’s new outcome. This behavioral flexibility is necessary to respond appropriately to changes in the environment and, as such, is an adaptive trait. The aim of this dissertation was to determine critical neural mechanisms specifically within the basolateral amygdala (BLA) and also with its interactions with the medial prefrontal cortex (mPFC) during behavioral flexibility when outcomes of learned appetitive cues change using the appetitive reversal learning paradigm. The main focus was on the BLA (Chapter 2) and its connection with the mPFC (Chapters 3 and 4) since both of these areas are critical in appetitive cue learning and valuation and subsequent behavioral modifications. The first study in this dissertation examined if separate neuronal ensembles within the BLA respond to different learned cues, a cue that signals food availability and a cue that does not. Additionally, we investigated if these potentially distinct neuronal ensembles are necessary during periods of behavioral flexibility when the value of the specific learned cues are changed during reversal learning. We determined that there are distinct neuronal ensembles within the BLA that respond to different learned cues, and that the cue-specific ensembles are necessary for updating the value of each specific cue (Chapter 2). Next, we examined a projection target of the BLA, the mPFC, to determine if BLA-projecting neurons are activated during learning (Chapter 3). Using retrograde tract tracing combined with Fos detection, we found recruitment of the anterior BLA to prelimbic area of the mPFC across cue-food learning, signifying that the BLA can inform the mPFC of the value of learned cues. Then to establish that communication between the BLA and mPFC is necessary for cue value learning and updating (Chapter 4), we functionally disconnected communication between these regions and examined appetitive learning using discriminative conditioning, reversal learning, and devaluation paradigms. We found impairments in cue value recall and subsequent updating of the cues’ values during reversal learning. Together, these studies indicate the BLA may be important in informing the mPFC of the value of learned cues, and their interaction is critical to optimally guide behavioral responding. The findings from these experiments are valuable for our understanding of the neural mechanisms that motivate eating behavior under the control of learned food cues and to understand the mechanisms necessary for behavioral flexibility when the outcomes of learned cues are changed. / Thesis (PhD) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Psychology.

Thesis advisor: Gorica D. Petrovich / Thesis advisor: Michael McDannald / Cues existing in the surrounding environment repeatedly paired with biologically relevant events can exert a powerful drive over behavior. When learned cues recurrently signal consumption, this can lead to eating in the absence of hunger or physiological need. The difficulties associated with resisting palatable foods and maintaining healthy habits may be related to the neurobiological underpinnings of pervasive responding to food cues. Behavioral flexibility through updating information about formed reward associations is vital to appropriately adapt to the surrounding environment and physiological need. Studying the renewal of responding of extinguished food-seeking behaviors can help us better understand the mechanisms mediating behavioral control over responding to learned reward cues. This dissertation aimed to explore behavioral sex differences and the neural substrates of renewal of responding to food cues after extinction by utilizing a context-mediated renewal of responding paradigm. The first chapter in this dissertation explored the effects of context habituation on context-induced renewal of responding to food cues in males and females. We investigated if increased familiarity with the behavioral contexts, and if presentation of food reward or not during these habituation sessions, would impact the strength of cue-food learning and renewal of responding after extinction differently in males and females. We discovered that when males received context habituation paired with food prior to training they exhibited elevated food-seeking behaviors throughout conditioning, as well as strengthened renewal. This suggests that for males the context habituation with food had a lasting, amplifying effect on cue-food learning. For females, however, increased context familiarity did not improve renewal of responding and, moreover, these experiments revealed evidence for resistance to extinguishing food-seeking behaviors in females. Then, in Chapter 2, we found neural evidence for potential plasticity mechanisms in the prelimbic (PL) and infralimbic (ILA) subregions, which were both recruited during context-mediated renewal of responding to food cues. Our findings are in line with evidence demonstrating that the PL and ILA are both recruited during appetitive learning and possibly provide overlapping contributions to encoding and responding in context-based reward learning. Taken together, the experiments outlined in this dissertation add to existing evidence of sex differences in appetitive motivated behaviors and the intricacies of the roles of the PL and ILA in cue-food learning and contextual processing. The findings from these studies advance our understanding of persistent food-seeking behaviors and highlight the importance of elucidating the neural substrates mediating behavioral responding to learned reward cues. / Thesis (PhD) — Boston College, 2022. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Psychology.