Behavioral evidence suggests that Asian elephants strongly rely on their sense of smell in a variety of contexts including foraging and social communication. Using a food-rewarded two-alternative operant conditioning procedure, three female Asian elephants were tested on their olfactory discrimination ability with 1-aliphatic alcohols, n-aldehydes, 2-ketones, n-carboxylic acids and with a set of twelve enantiomeric odor pairs. When presented with pairs of structurally related aliphatic odorants, the discrimination performance of the elephants increased with decreasing structural similarity of the odorants. Nevertheless, the animals successfully discriminated between all aliphatic odorants even when these only differed by one carbon atom. The elephants were also able to discriminate between all twelve enantiomeric odor pairs tested. Additionally, the elephants showed an excellent long-term odor memory and remembered the reward value of previously learned odor pairs after three weeks and one year of recess. Compared to other species tested previously on the same sets of odorants, the Asian elephants performed at least as good as mice and clearly better than human subjects, South African fur seals, squirrel monkeys, pigtail macaques, and honeybees. Taken together, these results support the notion that the sense of smell may play an important role in regulating the behavior of Asian elephants.

The sense of smell in marine mammals is traditionally thought to be poor. However, increasing evidence suggests that pinnipeds may use their sense of smell in a variety of behavioral contexts including communication, foraging, food selection, and reproduction. Using a food-rewarded two-choice instrumental conditioning paradigm, I assessed the ability of South African fur seals, Arctocephalus pusillus, to discriminate between 12 enantiomeric odor pairs, that is, between odorants that are identical in structure except for chirality. The fur seals significantly discriminated between eight out of the twelve odor pairs (according to p < 0.05, with carvone, dihydrocarvone, dihydrocarveol, limonene oxide, menthol, beta-citronellol, fenchone, and alpha-pinene), and failed with only four odor pairs (isopulegol, rose oxide, limonene, and camphor). No significant differences in performance were found between the animals (p > 0.05). Cross-species comparisons between the olfactory performance of the fur seals and that of other species previously tested on the same set of odor pairs lend further support to the notion that the relative size of the olfactory bulbs is not a reliable predictor of olfactory discrimination abilities. The results of the present study suggest that sense of smell may play an important and hitherto underestimated role in regulating the behavior of fur seals.

Le système constitué de la zone sous ventriculaire (ZSV) et du bulbe olfactif (BO) est l’une des deux régions cérébrales capables à l’âge adulte de produire de nouveaux neurones. La mise en évidence de cette neurogénèse adulte bulbaire a suscité un grand nombre d’interrogations quant à son rôle fonctionnel. Cependant les études réalisées dans ce domaine sont rares et contradictoires. L’objectif de cette thèse a été d’étudier l’impact de différentes expériences olfactives sur la neurogénèse afin de mieux comprendre son rôle fonctionnel. Nous avons choisi pour cela deux approches : d’une part l’étude de l’implication des néoneurones bulbaires lors de deux tâches d’apprentissage olfactif mettant en œuvre des odeurs neutres ; et d’autre part l’étude du rôle de ces néoneurones dans une situation de vie où l’olfaction joue un rôle primordial et où des variations de neurogénèse ont été rapportées: la maternité. Dans un premier temps, nous avons mis en évidence grâce à une stratégie d’anatomie fonctionnelle que les néoneurones de 5 semaines étaient recrutés lors d’un apprentissage de discrimination olfactive, mais pas lors de la restitution de cette information. Dans un deuxième temps, nous avons mis en évidence que la maternité améliorait les performances olfactives, et que cette amélioration était abolie par un stress gestationnel. Cependant, nous n’avons pas pu mettre en relation ces modifications de performances olfactives liées à la maternité et au stress avec des variations de neurogénèse. Nos travaux supportent l’hypothèse selon laquelle les néoneurones bulbaires sont impliqués dans la discrimination olfactive et mettent en évidence pour la première fois un impact de la maternité, qu’elle soit normale ou pathologique, sur les performances olfactives des mères. / In the mammalian brain, the subventricular zone (ZSV) and olfactory bulb (BO) system is a region where new neurons are continuously added throughout adulthood. While the functional consequences of continuous hippocampal neurogenesis have been extensively studied, the role of olfactory adult-born neurons remains more elusive. In particular, the involvement of these newborn neurons in odor discrimination and long-term odor memory is still a matter of debate. To address this question, we used two approaches. In the first one, we studied the recruitment of granular olfactory newborn neurons in two different tasks of olfactory learning with neutral odors. In the second one we studied the role of olfactory newborn neurons in a life situation where olfaction is crucial and where an increase in olfactory neurogenesis was reported, i.e. motherhood. In the first study, we found that odor discrimination learning recruited newborn neurons preferentially over preexisting ones, while odor memory restitution did not specifically activate newborn cells. Results of our second study indicate that motherhood improves olfactory memory and that this enhancement is abolished by a gestational stress. However, in our experimental conditions, we could not relate variations in neurogenesis with the modifications of olfactory performances linked to motherhood or stress. In conclusion our work brings new data in support of a functional role for newborn neurons in olfactory discrimination and shows for the first time an impact of motherhood, whether normal or pathological, on the olfactory performances of mothers.

There is little knowledge about olfactory learning in primates, even though primates are known to use olfaction in several behaviors including food selection and territorial defense. Therefore I assessed the olfactory learning and memory performance in five adult spider monkeys (Ateles geoffroyi) using a food-rewarded two-choice olfactory discrimination paradigm. The spider monkeys acquired the initial odor discrimination in 530-1102 trials and in a series of intramodal transfer tasks they needed 30-510 trials to reach the learning criterion. There was a significant negative correlation between the number of trials needed to reach the learning criterion and the number of transfer tasks completed. Thus, as a group, the animals displayed olfactory learning set formation. The number of trials that the spider monkeys needed in initial olfactory learning was comparable to that of other primate species tested previously but higher compared to that of other mammals such as dogs and rats. The learning speed of the spider monkeys in intramodal transfer tasks was similar to that of other mammals tested, suggesting that primates are less prepared to use olfactory cues in the initial solving of a problem but that once they learn the concept, their learning speed with novel odor discrimination problems is not generally slower than that of non-primate mammals. All spider monkeys tested reached the learning criterion in the memory tasks straight on the first testing day, that is: within 30 trials, suggesting similar long-term odor memory capabilities in spider monkeys and other mammals such as dogs, mice and rats.

O uso de estímulos olfativos em estudos de discriminação simples e complexa em ratos tem fornecido dados relevantes à área de controle de estímulos porque esta modalidade de estímulo é mais saliente à espécie do que as comumente utilizadas. O objetivo deste estudo foi investigar o efeito da combinação entre as modalidades de estímulo olfativa e auditiva sobre o responder discriminado em um procedimento de bloqueio de estímulos em ratos. Quatro ratos machos Wistar (Rattus norvegicus) foram treinados em três tarefas de discriminação de acordo com o delineamento de bloqueio de estímulos. Na Fase I discriminação prévia, dois ratos foram treinados usando estímulos auditivos (A+/A-) e outros dois usando estímulos olfativos (B+/B-) como S+/S-. Na Fase II discriminação de estímulo composto, um estímulo composto (A+B+/A-B-) foi usado como S+/S- e na Fase III discriminação pós-composto, os estímulos usados na Fase I foram removidos do composto e o treino continuou com os estímulos restantes. Em seguida, foram treinados em fases adicionais: IV - (mesmo treino da Fase II), V (mesmo treino da Fase III) e Fase VI em duas etapas primeira, treino com A+/A- e B+/B- na mesma sessão sem configuração de estímulo composto e segunda, treino de competição de dicas A+B- e B+A-. Todas as fases foram realizadas a partir de um procedimento Go/No-Go. Respostas em esquema de razão fixa três na condição S+ (A+, A+B+ e B+) foram consequenciadas com acesso à solução de sacarose e resposta na condição S- (A-, A-B- e B-) resultou em timeout de 2s após o final da tentativa. Não foi programada consequência específica para o não responder. Para todas as fases o critério de aquisição foi 90% ou mais de índice discriminativo. Na Fase I os resultados mostraram uma aquisição mais rápida do responder discriminado com estímulos olfativos. Os dados das Fases II e III indicaram que houve ocorrência de bloqueio de estímulos para todos os sujeitos, independente da ordem de treino com as modalidades de estímulos. As Fases IV e V indicaram uma replicação do fenômeno de bloqueio apesar do treino realizado na Fase III. A Fase VI sugeriu que o responder discriminado se diferenciou segundo o tipo de configuração de estímulo e que a repetição de bloqueio foi produzida pela discriminação prévia. Os resultados do estudo indicaram que a modalidade de estímulo foi determinante na aquisição de discriminação, mas não para bloqueio de estímulos, discordando da ideia de que odores não são bloqueados quando usados em estímulo composto em ratos e mostrando também que a saliência dos estímulos olfativos foi modulada pela discriminação prévia com outra modalidade / Use of olfactory stimuli in simple and complex discrimination studies with rats has produced important data to stimuli controls area because this stimulus modality is more salient than others usually used. The objective of this study was to investigate combinations effects between olfactory and auditory stimuli modalities on discriminative responding to stimuli blocking design. Four male Wistar rats (Rattus norvegicus) were trained in three discriminative tasks according to the stimuli blocking design. In Phase I prior discrimination, two rats were trained using auditory stimuli (A+/A-) and two rats using olfactory stimuli (B+/B-) as S+/S-. On Phase II compound stimulus discrimination, a compound stimuli (A+B+/A-B-) were used as S+/S- and in Phase III post-compound stimulus discrimination, the stimuli used on Phase I were remove from the compound. After discriminative training, subjects were trained on additional phases: Phase IV (same training Phase II), Phase V (same training Phase III) and Phase VI with two stages: first - A+/A- and B+/B- training presented in the same session without stimulus compound configuration, second - cue competition training (A+B- and B+A-).Discriminative training was carried under a Go/No-Go procedure. Responses on a fixed-ratio three schedule was reinforced by access to a sucrose solution when S+ (A+, A+B+ and B+) was presented and responding in S- (A-, A-B- and B-) resulted in 2s-timeout after trials ending. No consequence was programmed to non-responding. The acquisition criterion was a 90% or more discriminative index. Phase I data showed a discriminative responding acquisition faster with olfactory stimuli compared to auditory stimuli. Phases II and III data revealed stimuli blocking for all subjects regardless of training order with stimulus modalities. Phases IV and V showed a replication of stimuli blocking despite the training occurred on Phase III. Phase VI indicated that discriminative responding differed by type stimulus configuration presented and that stimulus blocking replication was produced by prior discrimination. Thus, results indicated that stimuli sensory modality was relevant for discriminative responding but not for blocking, disagreeing from the idea that odors are not blocked when it are used in compound stimulus in rat and showing also that olfactory stimulus saliency can be changed by prior discrimination training by other modality

O uso de estímulos olfativos em estudos de discriminação simples e complexa em ratos tem fornecido dados relevantes à área de controle de estímulos porque esta modalidade de estímulo é mais saliente à espécie do que as comumente utilizadas. O objetivo deste estudo foi investigar o efeito da combinação entre as modalidades de estímulo olfativa e auditiva sobre o responder discriminado em um procedimento de bloqueio de estímulos em ratos. Quatro ratos machos Wistar (Rattus norvegicus) foram treinados em três tarefas de discriminação de acordo com o delineamento de bloqueio de estímulos. Na Fase I discriminação prévia, dois ratos foram treinados usando estímulos auditivos (A+/A-) e outros dois usando estímulos olfativos (B+/B-) como S+/S-. Na Fase II discriminação de estímulo composto, um estímulo composto (A+B+/A-B-) foi usado como S+/S- e na Fase III discriminação pós-composto, os estímulos usados na Fase I foram removidos do composto e o treino continuou com os estímulos restantes. Em seguida, foram treinados em fases adicionais: IV - (mesmo treino da Fase II), V (mesmo treino da Fase III) e Fase VI em duas etapas primeira, treino com A+/A- e B+/B- na mesma sessão sem configuração de estímulo composto e segunda, treino de competição de dicas A+B- e B+A-. Todas as fases foram realizadas a partir de um procedimento Go/No-Go. Respostas em esquema de razão fixa três na condição S+ (A+, A+B+ e B+) foram consequenciadas com acesso à solução de sacarose e resposta na condição S- (A-, A-B- e B-) resultou em timeout de 2s após o final da tentativa. Não foi programada consequência específica para o não responder. Para todas as fases o critério de aquisição foi 90% ou mais de índice discriminativo. Na Fase I os resultados mostraram uma aquisição mais rápida do responder discriminado com estímulos olfativos. Os dados das Fases II e III indicaram que houve ocorrência de bloqueio de estímulos para todos os sujeitos, independente da ordem de treino com as modalidades de estímulos. As Fases IV e V indicaram uma replicação do fenômeno de bloqueio apesar do treino realizado na Fase III. A Fase VI sugeriu que o responder discriminado se diferenciou segundo o tipo de configuração de estímulo e que a repetição de bloqueio foi produzida pela discriminação prévia. Os resultados do estudo indicaram que a modalidade de estímulo foi determinante na aquisição de discriminação, mas não para bloqueio de estímulos, discordando da ideia de que odores não são bloqueados quando usados em estímulo composto em ratos e mostrando também que a saliência dos estímulos olfativos foi modulada pela discriminação prévia com outra modalidade / Use of olfactory stimuli in simple and complex discrimination studies with rats has produced important data to stimuli controls area because this stimulus modality is more salient than others usually used. The objective of this study was to investigate combinations effects between olfactory and auditory stimuli modalities on discriminative responding to stimuli blocking design. Four male Wistar rats (Rattus norvegicus) were trained in three discriminative tasks according to the stimuli blocking design. In Phase I prior discrimination, two rats were trained using auditory stimuli (A+/A-) and two rats using olfactory stimuli (B+/B-) as S+/S-. On Phase II compound stimulus discrimination, a compound stimuli (A+B+/A-B-) were used as S+/S- and in Phase III post-compound stimulus discrimination, the stimuli used on Phase I were remove from the compound. After discriminative training, subjects were trained on additional phases: Phase IV (same training Phase II), Phase V (same training Phase III) and Phase VI with two stages: first - A+/A- and B+/B- training presented in the same session without stimulus compound configuration, second - cue competition training (A+B- and B+A-).Discriminative training was carried under a Go/No-Go procedure. Responses on a fixed-ratio three schedule was reinforced by access to a sucrose solution when S+ (A+, A+B+ and B+) was presented and responding in S- (A-, A-B- and B-) resulted in 2s-timeout after trials ending. No consequence was programmed to non-responding. The acquisition criterion was a 90% or more discriminative index. Phase I data showed a discriminative responding acquisition faster with olfactory stimuli compared to auditory stimuli. Phases II and III data revealed stimuli blocking for all subjects regardless of training order with stimulus modalities. Phases IV and V showed a replication of stimuli blocking despite the training occurred on Phase III. Phase VI indicated that discriminative responding differed by type stimulus configuration presented and that stimulus blocking replication was produced by prior discrimination. Thus, results indicated that stimuli sensory modality was relevant for discriminative responding but not for blocking, disagreeing from the idea that odors are not blocked when it are used in compound stimulus in rat and showing also that olfactory stimulus saliency can be changed by prior discrimination training by other modality

The sense of smell plays an important role in regulating the behavior of Asian elephants but until now, no behavioral test to systematically assess the olfactory capabilities of this species existed. Using a voluntary, food-rewarded two-alternative operant conditioning procedure, three female Asian elephants were successfully taught to discriminate between rewarded and unrewarded odors and also succeeded in intramodal stimulus transfer tasks in which either the rewarded odor, or the unrewarded odor, or both odors were exchanged simultaneously for new odors. The animals readily mastered the initial task within only 120 stimulus contacts, demonstrating rapid olfactory learning and performing at least as good as rodents and dogs and even better than other species, including nonhuman primates, tested in similar studies before. When presented with pairs of structurally related odorants, the discrimination performance of the elephants decreased with increasing structural similarity of the odorants, but the animals still significantly discriminated between aliphatic acetic esters even when they only differed by one carbon chain length. The elephants also demonstrated an excellent long-term odor memory and successfully remembered the reward value of previously learned odor stimuli after two, four, eight and even 16 weeks of recess in testing. The paradigm developed and applied in the present study proved to be useful to assess the olfactory capabilities in Asian elephants.

Chez les mamifères terrestres, l’échantillonnage des odeurs (flairage) est inextricablement lié à la respiration. Le flairage contraint à la fois le décours temporel et l’intensité de l’input olfactif. Or le flaireage est un acte dynamique, il peut varier aussi bien en fréquence qu’en débit. Dans une 1ère partie de mon travail de thèse, nous avoins souhaité caractériser l’impact des variations de fréquence et de débit respiratiore sur l’activité du bulbe olfactif. Pour cela, nous avons mis au point une méthode de double trachéotomie chez le rat anesthésié nous permettant de contrôler précisément les flux d’air ans la cavité nasale. En paralèlle, nous avons enregistrer l’acitivité unitaire et de réseau du bulbe olfactif. Nous montrons que les variations de flairage modulent la représentation neuronale bulbaire des odeurs en modifiant à la fois l’activité de décharge des cellules principales et l’occurence des oscillaations du potentiel de champ local. Dans une 2e partie de ma thèse, nous avons souhaitécomprendre quel pouvait être le rôle du flairage chez un animal qui se comporte. Nous avons posé l’hypothèse qu’un animal pouvait adapter sa façon de flaireer en fonction de la qualité des molécules odorantes. Pour tester cette hypothèse, nous avons mis au point un système d’enregeistrement non invasif de la respiration couplé à une tâche de discrimination olfactive chez le rat. Nous montrons non seulement que les animaux peuvent adapter leur flairage en fonction des molécules odorantes masi également en focntion du contexte dans lequel l’odeur est présentée. L’ensemble de ces résultats s’intègre donc dans la problématique plus générale de l’intégration sensori-motrice. / In terrestrial mammals, an inextricable link between olfaction and respiration exists due to the periodic sampling of odorant molecules by inhalation. The features of sniffing (or breathing) constrain both the timing and the intensity of the input to the olfactory structures. But rather than being fixed, sniffing in the bahavingrodent is highly dynamic and varies both in frequency and flow rate. During the firs stage of my PhD, I asked to what extent sniffing parameters (frequency and flow rate) variations could affect the olfactory bulb activity. To address this question, I developped a double tracheotomy protocol in anesthetized rats to precisely control and modify the nasal airflow. In parallel, I recorded oldfactory bulbactivities, single-unit activity and local field potentials. We showed that, at the olfactory bulb level, the neutral representation of an odor is highly modified by sampling variations. In fact both the mitral/tufted cell discharge patterns and local field potentials oscilliations were affected by sniffing variations. In the second stage, we wanted to understand the role of sniffing variations in behaving animals. We hypothesized tha t an animal could adapt its sniffing strategy relative to the quality of the odorant molecules. To test this hypothesis, we developped a tool to record sniffing in a non invasive way, and combined it to an olfactory discrimination task in the rat. We showed that animals not only adapted their sniffing relative to the odorant quality but also to the odorant context. Taken together, these results fit into the broader context of sensory-motor integration.