Letteratura scientifica selezionata sul tema "Olfactory perceptual learning"

Defining perceptual similarity metrics for odorant comparisons is crucial to understanding the mechanism of olfactory perception. Current methods in olfaction rely on molecular physicochemical features or discrete verbal descriptors (floral, burnt, etc.) to approximate perceptual (dis)similarity between odorants. However, structural or verbal descriptors alone are limited in modeling complex nuances of odor perception. While structural features inadequately characterize odor perception, language-based discrete descriptors lack the granularity needed to model a continuous perception space. We introduce data-driven approaches to perceptual metrics learning (PMeL) based on two key insights: a) by combining physicochemical features with the user’s perceptual feedback, we can leverage both structural and perceptual attributes of odors to define dissimilarity, and b) instead of discrete labels, user’s perceptual feedback can be gathered as relative similarity comparisons, such as “Does molecule-A smell more like molecule-B, or molecule-C?” These triplet comparisons are easier even for non-experts users and offer a more effective representation of the continuous perception space. Experimental results on several defined tasks show the effectiveness of our approach in evaluating perceptual dissimilarity between odorants. Finally, we investigate how closely our model, trained on non-expert feedback, aligns with the expert’s similarity judgments. Our effort aims to reduce reliance on expert annotations.

Research Problem: The purpose of this research synthesis is to identify new opportunities for smell-enabled games based upon current olfactory research, and to present early game concepts that have emerged from our empirical assessments. Literature Review: We briefly summarize key projects in the history of scent technologies for film and media. Human-Computer Interaction researchers have also explored a number of uses for scent delivery in interactive digital media. Recent developments in olfactory psychology and neuroscience research suggest that a fruitful avenue for exploration is to develop learning games that expand olfactory capacity. Methodology: We have conducted two studies of computer-based perceptual and cognitive olfactory tasks. Mixture perception experiment: We designed a perceptual experiment where the task was to correctly estimate the intensity of odor components in a blend of coffee and tea. Blended odors were presented to 10 healthy adults by means of a computer-controlled olfactometer. Following each stimulation, the participant used a computer interface to estimate the intensity of components of the blend. Event-based memory experiment: We have developed a digital olfactory version of the children’s game “Memory.” The game interface consists of 32 white squares that are presented in a grid pattern on the screen and that, when participants click on them, triggers the release of one of eight possible smells from the olfactometer. Fifteen healthy adult participants were tested in 10 laboratory sessions distributed over three weeks. Results and Conclusions: Our empirical results suggest that smell training through learning games holds promise as a means of improving cognitive function. The results of our event-based memory experiment suggest that both olfactory and visual memory capacities might have benefitted from olfactory game training. The results of our mixture perception experiment indicate that binary odor mixtures might provide a suitable starting point for perceptual training, and we suggest that a smell-enabled game might include adaptive difficulty by progressively introducing more complex mixtures. We have used event-based memory and mixture perception as “olfactory targets” for game mechanic development, and present early design concepts for “Smelly Genes” and “Scenter.” Finally, we discuss future directions and challenges for this new, interdisciplinary research topic.

Addition of newly generated neurons into mature neural circuits in the adult CNS responds to changes in neurotransmitter levels and is tightly coupled to the activity of specific brain regions. This postnatal neurogenesis contributes to plasticity of the olfactory bulb and hippocampus and is thought to play a role in learning and memory, context and odor discrimination, as well as perceptual learning. While acetylcholine plays an important role in odor discrimination and perceptual learning, its role in adult neurogenesis in the olfactory bulb has not been elucidated. In this study, I have examined the functional expression of nAChRs in progenitor cells of the rostral migratory stream (RMS) in the adult olfactory bulb of mice. I show that most of these cells in the RMS exhibit large nAChR-mediated calcium transients upon application of acetylcholine (ACh). Unlike in the hippocampus, the predominant functional nAChRs on progenitor cells are of α3β4 subtype. Interestingly, functional receptor expression is lost once progenitor cells mature, and are incorporated into the granule cell layer. Instead, nAChRs are now expressed on some presynaptic terminals and modulate glutamate release onto granule cells. My results imply that ACh is a part of the permissive niche and likely plays a role in development of progenitor cells.

Le bulbe olfactif est le siège d'une neurogenèse adulte pouvant jouer un rôle dans les apprentissages olfactifs. Nous nous sommes intéressés à son rôle dans un type d'apprentissage olfactif : l'apprentissage perceptif. Tout d'abord, l'enrichissement permet d'améliorer la discrimination d'odeurs proches : c'est l'apprentissage perceptif. En étudiant les effets de la suppression de la neurogenèse pendant l'enrichissement nous avons montré que la neurogenèse était nécessaire à l'apprentissage perceptif en modulant l'inhibition des cellules mitrales par les cellules granulaires. Ensuite, nous avons étudié le rôle de la noradrénaline dans cet apprentissage. La noradrénaline est nécessaire à l'apprentissage perceptif et suffisante pour en mimer les effets. De plus, nous avons montré que la neurogenèse bulbaire était essentielle à l'action de la noradrénaline pour permettre l'apprentissage perceptif. Enfin, nous nous sommes intéressés à l'effet du vieillissement sur l'apprentissage perceptif. Nous avons trouvé qu'il existait un défaut d'apprentissage perceptif chez la souris âgée en lien avec une diminution de la neurogenèse. En revanche, une stimulation noradrénergique permet de restaurer l'apprentissage perceptif sans modulation de la neurogenèse bulbaire suggérant l'existence de mécanismes compensatoires. L'apprentissage perceptif est sous-tendu par la neurogenèse bulbaire, via le système noradrénergique, pour permettre une hausse d'inhibition des cellules mitrales par les cellules granulaires améliorant la discrimination des odeurs proches. Avec l'âge, l'apprentissage perceptif peut être restauré suggérant une plasticité toujours présente dans un système olfactif vieillissant
The olfactory bulb is the target of a well described adult neurogenesis which has been involved in different kinds of learning. We focused on the role of adult neurogenesis on olfactory perceptual learning which consists on an improvement of olfactory discrimination after odor enrichment. We found that experience-driven improvement in olfactory discrimination (perceptual learning) requires the addition of newborn neurons in the olfactory bulb. More specifically, we showed that adult-born neurons are required for perceptual learning by modulating the inhibition of mitral cells by granule cells. Then, we studied the role of noradrenaline on perceptual learning. Direct manipulation of noradrenergic transmission significantly effect on adult-born neuron survival and perceptual learning. Finally, we investigated the effect of aging on perceptual learning. We found that perceptual learning was impaired by aging in line with an alteration of neurogenesis. However, noradrenergic stimulation restores perceptual learning without modulating neurogenesis suggesting compensatory mechanisms. Neural mechanisms underlying perceptual learning involve neurogenesis and noradrenergic system to allow an increase of mitral cell inhibition thanks to the granule cells leading to an improvement of odor discrimination. During aging, perceptual learning can be restored suggesting that the olfactory system is still plastic

Les comportements sont codés par des circuits neuronaux, englobant le cerveau, qui changent avec l'âge et l'expérience. L'immunodétection du gène c-Fos est utilisée depuis des décennies pour révéler les circuits neuronaux activés lors de tâches ou de conditions spécifiques. La méthode c-Fos présente cependant deux limites : 1) L'expression du c-Fos est limitée dans le temps. 2) Les quantifications sont chronophages et souvent limitées à une seule région cérébrale. Le premier objectif de ma thèse consistait à relever les défis actuels liés à l’étude de l'activité neuronale impliquée dans différents comportements à l’échelle du cerveau entier. Ainsi, j'ai développé un workflow contournant les limitations temporelles et spatiales associées à c-Fos. La combinaison de l’expression c-Fos avec celle de tdTomato, Cre-dépendante du c-Fos (souris TRAP2), m’a permis de visualiser et d'effectuer une comparaison directe des circuits neuronaux activés à différents moments ou au cours de différentes tâches. En utilisant des logiciels libres d’acces (QuPath et ABBA), j'ai établi un workflow qui optimise et automatise la détection des cellules, leur classification (c-Fos vs. c-Fos/tdTomato) et l'enregistrement du cerveau entier. Ce workflow automatique, basé sur des scripts entièrement automatisés, permet une quantification précise du nombre de cellules avec une variabilité interindividuelle minimale. De plus, l'interrogation d’atlas cérébraux à différentes échelles (de simplifiée à détaillée) a été réalisée, permettant un zoom progressif sur des régions cérébrales définies afin d'explorer la distribution spatiale des cellules activées. Enfin, j'ai illustré le potentiel de cette approche en comparant les schémas d'activation neuronale dans divers contextes (états de vigilance, comportement social) dans des groupes d'animaux distincts ainsi qu'au sein des mêmes animaux. Enfin, BrainRender a été utilisé pour la représentation intuitive des résultats obtenus. Ainsi ce workflow automatisé et accessible à tous les laboratoires ayant une expérience en histologie permet une analyse impartiale, rapide et précise de l'ensemble du modèle d'activité cérébrale au niveau cellulaire, dans différents contextes. Mon deuxième objectif consistait à étudier l'interdépendance de comportements spécifiques par l’étude des effets de la privation de sommeil paradoxal sur l'apprentissage perceptif olfactif. Cette tâche d'apprentissage est définie comme une capacité à discriminer entre deux odorants perceptivement similaires après une exposition passive à celles-ci pendant 10 jours, un processus partiellement dépendant de la neurogenèse adulte. c-Fos, en combinaison avec l’expression de tdTomato (souris TRAP2), m’a permis de visualiser l'activité neuronale avant et après l'apprentissage perceptif. Une privation de sommeil paradoxal automatisée pendant 4 heures par jour après cet apprentissage à permis d’observer une absence de discrimination olfactive. Ainsi sont posées des bases solides pour de futures études, impliquant notre workflow automatisé pour évaluer l'activité neuronale dans le bulbe olfactif et les centres olfactifs supérieurs du cerveau. En outre, le rôle des nouveaux neurones et l'impact de la privation de sommeil paradoxal sur leurs schémas d'activité seront explorés ultérieurement. En conclusion, le travail présenté dans ma thèse apporte des avancées méthodologiques significatives en développant un workflow automatisé sur l'ensemble du cerveau pour visualiser et comparer les circuits neuronaux activés dans différents comportements. Ainsi, l'exploration de l'impact de la privation de sommeil paradoxal sur l’apprentissage perceptif olfactif met en évidence la relation complexe entre le sommeil et le traitement sensoriel, posant les bases de futures recherches sur les mécanismes neuronaux qui sous-tendent ces processus
Behaviors are encoded by widespread neural circuits within the brain which change with age and experience. Immunodetection of the immediate early gene c-Fos has been used for decades to reveal neural circuits activated during specific tasks or conditions. While successful, c-Fos method presents two limitations: 1) c-Fos expression is restricted in time, and cannot be used to follow up the same neurons activation over time or in response to different stimuli. 2) Quantifications are time consuming and often performed for a single brain region which restricts spatial information. A first objective of my thesis consisted in addressing challenges associated with whole brain probing of neuronal activity involved in higher sensory information processing. To this end, I developed and benchmarked a workflow that circumvents temporal and spatial limitations associated with c-Fos quantification. I combined c-Fos with c-Fos driven Cre-dependent tdTomato expression (i.e. TRAP2 mice), to perform a direct comparison of neural circuits activated at different times or during different tasks. Using open-source softwares (i.e. QuPath and ABBA), I established a workflow that optimize and automate cell detection, cell classification (e.g. c-Fos vs. c-Fos/tdTomato) and whole brain registration. This automatic workflow, based on fully automatic scripts, allows accurate quantification with minimal interindividual variability. Further, interrogation of brain atlases at different scales (from simplified to detailed) was performed, allowing a gradual zoom on defined brain regions to explore the spatial distribution of activated cells. I finally illustrated the potential of this approach by comparing patterns of neuronal activation in various contexts, i.e. wakefulness, paradoxical sleep and social interaction tasks, in distinct animal groups as well as within the same animals. Finally, BrainRender was used for intuitive representation of obtained results. Altogether, this automated workflow accessible to all labs with some experience in histology, allows an unbiased, fast and accurate analysis of the whole brain activity pattern at the cellular level, in various contexts. As an extension of this work, the second objective of my PhD focused on investigating the interdependence of specific behaviours. To this end, I studied effects of paradoxical sleep deprivation on olfactory perceptual learning. This learning task is defined as an enhanced ability to discriminate between two perceptually similar odorants following passive exposure to these 2 odorants for 10 days, a process partially reliant on adult neurogenesis. I used c-Fos immunohistochemistry in combination with tdTomato expression (TRAP2 mice), to visualize neuronal activity before and after perceptual learning. I have implemented a chronic automated paradoxical sleep deprivation for 4 hours per days following the olfactory perceptual learning protocol. Our behavioural data revealed that paradoxical sleep deprivation altered the improvement of odour discrimination. This work lays a solid foundation for future studies, which will extend the automated workflow I developed to evaluate neuronal activity within the olfactory bulb, as well as in higher olfactory centres in the brain. Additionally, the role of adult-born neurons and the potential impact of paradoxical sleep deprivation on their activity patterns will be explored further. In conclusion, the work presented in my thesis provides significant advancements in addressing the limitations of traditional c-Fos quantification methods by developing an automated, whole-brain workflow to visualize and compare neural circuits activated under different conditions. Furthermore, the exploration of the impact of paradoxical sleep deprivation on perceptual learning highlights the intricate relationship between sleep and sensory processing, laying the groundwork for future investigations into the neural mechanisms underlying these processes

A great degree of interindividual variability has been established in measures of psychophysical olfactory performance and odor awareness in both children and adults. Previous studies have suggested the possibility that one of the factors that might contribute to this variability might be the degree of odor exposure in everyday contexts. In the present study, we hypothesized that children exposed to a greater variety of odors on a more frequent basis would exhibit higher odor identification and odor awareness scores. We have found an effect of odor exposure on the children's olfactory knowledge as reflected in their reports of olfactory behavior, but not olfactory abilities. In so doing, we replicated some of the previous findings in the literature of female over male advantage in the olfactory domain. Namely, we report that girls showed a more profound understanding of their olfactory environment and a greater degree of olfaction-oriented behavior, which was not accounted for by a gender difference in verbal fluency. Nevertheless, girls did not outperform boys on either of the measures of olfactory performance. Semi-longitudinal and longitudinal studies in verbally proficient children, employing both self- and parental reports of children's odor exposure and repeated olfactory testing, might...