Odeur

Résumé

Une odeur est le résultat, perçu par le sens de l’odorat, de l’émanation des corps volatils contenus dans certaines substances comme les molécules souvent qualifiées de molécules odorantes ou de parfum, ou de fragrance dans le cas des fleurs. Les aérosols (particules solides ou liquides) dégagent aussi une odeur (vapeur, fumée). Nature chimique Les molécules odorantes sont caractérisées par leur composition chimique.

Le/les composés organiques : alcool, acide, aldéhyde, cétone, composé aromatique
La longueur : nombre de carbones constitutifs de la chaîne principale.
L’organisation spatiale : isomère, énantiomère.

Les signaux odorants peuvent être répartis dans différentes classes. Chez les espèces aquatiques, les composés générateurs d’odeurs sont en majorité des acides aminés ou des sels biliaires. Perception Un être humain brasse en moyenne d’air par jour à raison de , ce qui lui donne la capacité de détecter quotidiennement un nombre très élevé d

Source officielle

https://fr.wikipedia.org/wiki/Odeur

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Séances de cours associées (17)

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Collective search of a single odour source using cooperation

Alexandre Herrmann

We study coordination strategies for a multirobot team. The goal is to find the source of an odour most efficiently in terms of the distance travelled by the robots and the time required to discover the source. We focus on the problem of finding the source of the odour once a robot has already found the plume of this odour. The results show that the studied algorithms are effective in non-homogeneous wind models, which include turbulences.

2007

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Analysis of information processing in the olfactory bulb by in vivo experiments and theoretical modelling

Brice Bathellier

Much information is conveyed to animals by the diverse molecules propagated in their environment. This information is transmitted and treated within the olfactory system to be utilized by the rest of the brain. In this process, the sensory flow arriving from the nose first encounters the olfactory bulb. This thesis studies different aspects of the encoding and treatment of olfactory information in the bulb by a combination of experimental and theoretical approaches. The olfactory bulb consists of two functional stages: an input stage where the nerve terminals from the sensory neurons of the nose are spatially arranged in a precise manner, and an output stage corresponding to the neurons which propagate the processed information towards the more central brain areas. The first part of this thesis is focused on the development of an image processing technique to precisely map the input stage. In a second part, output neurons activity in responsive areas of the bulb was recorded in anaesthetized mice. The data obtained indicate complex dynamics in neural activity on several time scales. We show that the combination of mean firing rates from a large enough ensemble of neurons allows to accurately predict the odor presented to the animal. We also show that temporal variables related to the dynamics give very little information complementary to the ensemble rate code, suggesting that these variables are not read by brain structures downstream to the bulb. In a third part, we developed a numerical model of the olfactory bulb to understand its fast oscillatory dynamics. The model proposes a mechanism based on the negative feedback from the interneurons that regulate output neurons. Some predictions of the model are checked experimentally. An analytical interpretation of the model is also proposed and its generalization to the analysis of fast oscillation in other parts of the brain is discussed.

EPFL2007

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To sense myriad environmental odors, animals have evolved multiple, large families of divergent olfactory receptors. How and why distinct receptor repertoires and their associated circuits are functionally and anatomically integrated is essentially unknown. We have addressed these questions through comprehensive comparative analysis of the Drosophila olfactory subsystems that express the ionotropic receptors (IRs) and odorant receptors (ORs). We identify ligands for most IR neuron classes, revealing their specificity for select amines and acids, which complements the broader tuning of ORs for esters and alcohols. IR and OR sensory neurons exhibit glomerular convergence in segregated, although interconnected, zones of the primary olfactory center, but these circuits are extensively interdigitated in higher brain regions. Consistently, behavioral responses to odors arise from an interplay between IR- and OR-dependent pathways. We integrate knowledge on the different phylogenetic and developmental properties of these receptors and circuits to propose models for the functional contributions and evolution of these distinct olfactory subsystems.

2011

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Analysis of information processing in the olfactory bulb by in vivo experiments and theoretical modelling

Brice Bathellier

EPFL2007