Olfactory preference conditioning changes the reward value of reinforced and non-reinforced odors

International audienceOlfaction is determinant for the organization of rodent behavior. In a feeding context, rodents must quickly discriminate whether a nutrient can be ingested or whether it represents a potential danger to them. To understand the learning processes that support food choice, aversive olfactory learning and flavor appetitive learning have been extensively studied. In contrast, little is currently known about olfactory appetitive learning and its mechanisms. We designed a new paradigm to study conditioned olfactory preference in rats. After 8 days of exposure to a pair of odors (one paired with sucrose and the other with water), rats developed a strong and stable preference for the odor associated with the sucrose solution. A series of experiments were conducted to further analyze changes in reward value induced by this paradigm for both stimuli. As expected, the reward value of the reinforced odor changed positively. Interestingly, the reward value of the alternative odor decreased. This devaluation had an impact on further odor comparisons that the animal had to make. This result suggests that appetitive conditioning involving a comparison between two odors not only leads to a change in the reward value of the reinforced odor, but also induces a stable devaluation of the non-reinforced stimulus

Reshaping of Bulbar Odor Response by Nasal Flow Rate in the Rat

The impact of respiratory dynamics on odor response has been poorly studied at the olfactory bulb level. However, it has been shown that sniffing in the behaving rodent is highly dynamic and varies both in frequency and flow rate. Bulbar odor response could vary with these sniffing parameter variations. Consequently, it is necessary to understand how nasal airflow can modify and shape odor response at the olfactory bulb level.To assess this question, we used a double cannulation and simulated nasal airflow protocol on anesthetized rats to uncouple nasal airflow from animal respiration. Both mitral/tufted cell extracellular unit activity and local field potentials (LFPs) were recorded. We found that airflow changes in the normal range were sufficient to substantially reorganize the response of the olfactory bulb. In particular, cellular odor-evoked activities, LFP oscillations and spike phase-locking to LFPs were strongly modified by nasal flow rate.Our results indicate the importance of reconsidering the notion of odor coding as odor response at the bulbar level is ceaselessly modified by respiratory dynamics

Energy decay in a transmission problem in thermoelasticity of type III

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Energy decay in a Timoshenko-type system with history in thermoelasticity of type III

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Blowup of solutions with positive energy in nonlinear thermoelasticity with second sound

This work is concerned with a semilinear thermoelastic system, where the heat flux is given by Cattaneo's law instead of the usual Fourier's law. We will improve our earlier result by showing that the blowup can be obtained for solutions with relatively positive initial energy. Our technique of proof is based on a method used by Vitillaro with the necessary modifications imposed by the nature of our problem

Nonlinear damped Timoshenko systems with second sound : global existence and exponential stability

In this paper, we consider nonlinear thermoelastic systems of Timoshenko type in a one-dimensional bounded domain. The system has two dissipative mechanisms being present in the equation for transverse displacement and rotation angle - a frictional damping and a dissipation through hyperbolic heat conduction modelled by Cattaneo's law, respectively. The global existence of small, smooth solutions and the exponential stability in linear and nonlinear cases are established

Learning-induced oscillatory activities correlated to odour recognition: a network activity

International audienceIn trained behaving rats, the expression of a prominent beta oscillatory activity in the olfactory system was previously identified as a correlate of odour recognition. The aim of the present study was to assess the putative role of a functional coupling between the olfactory bulb (OB) and higher structures in this activity. We performed a unilateral inactivation of the medial part of the olfactory peduncle by lidocaine infusion. Inactivation deprived the OB from most of its centrifugal afferences, including feedback connections from the piriform cortex (PC) while sparing the ascending fibres from the OB to higher cortical structures. This treatment reduced the amplitude of odour-induced oscillatory beta responses both in OB and PC. In parallel, gamma activity classically observed in these two structures during spontaneous activity displayed a strong enhancement. Results suggest that odour-induced oscillatory response could be the emergent feature of an olfactory functional network set up through learning

General decay of solutions of a nonlinear system of viscoelastic wave equations

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Learning-induced modulation of oscillatory activities in the mammalian olfactory system: The role of the centrifugal fibres

International audienceIn the mammalian olfactory system, oscillations related to odour representation have been described in field potential activities. Previous results showed that in olfactory bulb (OB) of awake rats engaged in an olfactory learning, odour presentation produced a decrease of oscillations in gamma frequency range (60-90 Hz) associated with a power increase in beta frequency range (15-40 Hz). This response pattern was strongly amplified in trained animals. The aim of this work was twofold: whether learning also induces similar changes in OB target structures and whether such OB response depends on its centrifugal inputs. Local field potentials (LFPs) were recorded through chronically implanted electrodes in the OB, piriform and enthorhinal cortices of freely moving rats performing an olfactory discrimination. Oscillatory activities characteristics (amplitude, frequency and time-course) were extracted in beta and gamma range by a wavelet analysis. First, we found that odour induced beta oscillatory activity was present not only in the OB, but also in the other olfactory structures. In each recording site, characteristics of the beta oscillatory responses were dependent of odour, structure and learning level. Unilateral section of the olfactory peduncle was made before training, and LFPs were symmetrically recorded in the two bulbs all along the acquisition of the learning task. Data showed that deprivation of centrifugal feedback led to an increase of spontaneous gamma activity. Moreover, under this condition olfactory learning was no longer associated with the typical large beta band. As a whole, learning modulation of the beta oscillatory response in olfactory structures may reflect activity of a distributed functional network involved in odour representation

Le simulateur de perte auditive, le plus rapide de l’ouest

National audienceLe simulateur de perte auditive développé au laboratoire est basé sur les travaux d'Irino et Patterson, notamment le modèle Dynamic Compressive Gammachirp (CGC). En pratique le CGC est une cascade de filtres pour 32 canaux en parallèle. Chaque canal est constitué d’un filtre auditif passe-bande (Gammachirp) suivit d’un filtre auditif passe-haut (HPAF). La fréquence de coupure de chaque HPAF est contrôlée par le niveau en décibel dans la bande. C'est ce mécanisme qui simule la compression. Appliqué avec les gains inversés, on obtient le InvCGC qui lui annule ainsi la compression naturelle de l’oreille. Dans le cadre de l’ANR Aida, nous avons adapté et récrit cet algorithme en python/OpenCL pour l’adapter aux calculs en parallèle sur processeurs graphiques (GPU). Ce code en licence libre peut être utilisé sur tout PC équipé d’un GPU et d’une carte son adéquate. Ce simulateur peut aussi être utilisé via une « carte son wifi » développé au labo (faible latence/sans compression). Le système total (carte son wifi + tablette PC + casque actif + micro) nous permet ainsi d’avoir une version portable du simulateur. Muni de ce simulateur, un auditeur normo-entendant peut tester, en situation, le rendu d’une perte auditive