Prandial states modify the reactivity of the gustatory cortex using gustatory evoked potentials in humans

Previous functional Magnetic Resonance Imaging studies evaluated the role of satiety on cortical taste area activity and highlighted decreased activation in the orbito-frontal cortex when food was eaten until satiation. The modulation of orbito-frontal neurons (secondary taste area) by ad libitum food intake has been associated with the pleasantness of the food's flavor. The insula and frontal operculum (primary taste area) are also involved in reward processing. The aim was to compare human gustatory evoked potentials (GEP) recorded in the primary and secondary gustatory cortices in a fasted state with those after food intake. Fifteen healthy volunteers were enrolled in this observational study. In each of two sessions, two GEP recordings were performed (at 11:00 am and 1:30 pm) in response to sucrose gustatory stimulation, and a sucrose-gustatory threshold was determined. During one session, a standard lunch was provided between the two GEP recordings. During the other session, subjects had nothing to eat. Hunger sensation, wanting, liking, and the perception of the solution's intensity were evaluated with visual analog scales. GEP latencies measured in the Pz (p < 0.001), Cz (p < 0.01), Fz (p < 0.001) recordings (primary taste area) were longer after lunch than in the pre-prandial condition. Fp1 and Fp2 latencies (secondary taste area) tended to be longer after lunch, but the difference was not significant. No difference was observed for the sucrose-gustatory threshold regardless of the session and time. Modifications in the primary taste area activity during the post-prandial period occurred regardless of the nature of the food eaten and could represent the activity of the frontal operculum and insula, which was recently shown to be modulated by gut signals (GLP-1, CCK, ghrelin, or insulin) through vagal afferent neurons or metabolic changes of the internal milieu after nutrient absorption. This trial was registered at clinicalstrials.gov as NCT02472444

Etude du contrôle hédonique de la prise alimentaire par l'analyse des potentiels évoqués gustatifs

Hedonic control of food intake has been studied using neurophysiological investigations in animals and functional imaging in humans. Gustatory evoked potentials (GEPs), a higher time resolution technique than functional imaging, have never been used for this purpose. The first aim of this thesis was to establish a reliable recording of GEPs in humans, in response to a sapid stimulus. The second aim was to determine the GEPs modifications according to the hedonic value of food intake. GEPs recording was performed in response to an intermittent stimulation of a sapid solution in more than 100 young healthy subjects. The comparisons between cerebral recordings in response to water or paraffin oil, non palatable solutions, and in response to sapid solutions (sucrose, sodium chlorure and fatty acids) allow us to advance strong arguments for the gustative nature of the recorded evoked potentials. GEPs analysis underlined changes in cerebral activation according to the hedonic value of the stimulus. These changes in cerebral activation were highlighted by modifications of GEPs latency or amplitude. Several physiological situations, marked by different pleasantness of food stimulation, were studied: before/after food intake, stimulation by sweet solutions with different concentrations or different caloric contents, stimulation by fatty acids. Moreover, GEPs in response to long chain fatty acids (linoleic acids) were recorded, reinforcing the hypothesis that fatty acids could be the sixth primary flavor.Les techniques d’électrophysiologie chez les animaux et d’imagerie fonctionnelle chez l’Homme ont permis d’étudier le contrôle hédonique de la prise alimentaire. Ce contrôle hédonique n’a cependant jamais été exploré chez l’Homme par l’étude des potentiels évoqués gustatifs (PEG), de meilleure résolution temporelle que l’imagerie fonctionnelle. Le premier objectif de la thèse a été de mettre au point une technique fiable et reproductible de recueil des PEG, en regard des aires cérébrales gustatives, en réponse à une stimulation sapide. Le deuxième objectif a été d’étudier les variations des PEG en fonction de la valeur hédonique de la prise alimentaire. Le travail de thèse a permis de mettre au point l’enregistrement des PEG, réalisés chez plus de 100 jeunes sujets sains. Les comparaisons effectuées entre les enregistrements cérébraux obtenus en réponse à l’eau seule ou à l’huile de paraffine, solutions non palatables, et après stimulation par une solution sapide ont permis d’apporter des arguments forts en faveur de l’origine gustative des potentiels évoqués enregistrés. L’analyse des PEG a permis de mettre en évidence des modifications de l’activation cérébrale en fonction du plaisir alimentaire, traduites par des changements de latence ou d’amplitude des PEG. Plusieurs situations connues pour faire varier le plaisir alimentaire ont été étudiées : avant/après repas ; stimulation par des solutions sucrées d’intensités différentes ou de valeurs énergétiques différentes ; stimulation par des acides gras. Des PEG en réponse aux acides gras à longue chaine (acides linoléiques) ont été enregistrés par ce biais, renforçant l’hypothèse du «gras» en tant que sixième saveur primaire

Study of hedonic control of food intake using gustatory evoked potentials

Les techniques d’électrophysiologie chez les animaux et d’imagerie fonctionnelle chez l’Homme ont permis d’étudier le contrôle hédonique de la prise alimentaire. Ce contrôle hédonique n’a cependant jamais été exploré chez l’Homme par l’étude des potentiels évoqués gustatifs (PEG), de meilleure résolution temporelle que l’imagerie fonctionnelle. Le premier objectif de la thèse a été de mettre au point une technique fiable et reproductible de recueil des PEG, en regard des aires cérébrales gustatives, en réponse à une stimulation sapide. Le deuxième objectif a été d’étudier les variations des PEG en fonction de la valeur hédonique de la prise alimentaire. Le travail de thèse a permis de mettre au point l’enregistrement des PEG, réalisés chez plus de 100 jeunes sujets sains. Les comparaisons effectuées entre les enregistrements cérébraux obtenus en réponse à l’eau seule ou à l’huile de paraffine, solutions non palatables, et après stimulation par une solution sapide ont permis d’apporter des arguments forts en faveur de l’origine gustative des potentiels évoqués enregistrés. L’analyse des PEG a permis de mettre en évidence des modifications de l’activation cérébrale en fonction du plaisir alimentaire, traduites par des changements de latence ou d’amplitude des PEG. Plusieurs situations connues pour faire varier le plaisir alimentaire ont été étudiées : avant/après repas ; stimulation par des solutions sucrées d’intensités différentes ou de valeurs énergétiques différentes ; stimulation par des acides gras. Des PEG en réponse aux acides gras à longue chaine (acides linoléiques) ont été enregistrés par ce biais, renforçant l’hypothèse du «gras» en tant que sixième saveur primaire.Hedonic control of food intake has been studied using neurophysiological investigations in animals and functional imaging in humans. Gustatory evoked potentials (GEPs), a higher time resolution technique than functional imaging, have never been used for this purpose. The first aim of this thesis was to establish a reliable recording of GEPs in humans, in response to a sapid stimulus. The second aim was to determine the GEPs modifications according to the hedonic value of food intake. GEPs recording was performed in response to an intermittent stimulation of a sapid solution in more than 100 young healthy subjects. The comparisons between cerebral recordings in response to water or paraffin oil, non palatable solutions, and in response to sapid solutions (sucrose, sodium chlorure and fatty acids) allow us to advance strong arguments for the gustative nature of the recorded evoked potentials. GEPs analysis underlined changes in cerebral activation according to the hedonic value of the stimulus. These changes in cerebral activation were highlighted by modifications of GEPs latency or amplitude. Several physiological situations, marked by different pleasantness of food stimulation, were studied: before/after food intake, stimulation by sweet solutions with different concentrations or different caloric contents, stimulation by fatty acids. Moreover, GEPs in response to long chain fatty acids (linoleic acids) were recorded, reinforcing the hypothesis that fatty acids could be the sixth primary flavor

Evolution de l'aphasie après thrombolyse intra-veineuse à la phase aiguë des infarctus cérébraux

DIJON-BU Médecine Pharmacie (212312103) / SudocSudocFranceF

Perception des acides gras et potentiels évoqués gustatifs : application dans l’obésité

International audienceFat taste as a primary taste is a new concept which can affect feeding behavior. Free fatty acids could activate the gustatory afferent pathway as another primary taste (sweet, salt, bitter, sour, umami). Our team demonstrates this activation by recording cerebral gustatory evoked potentials, in response to several solutions of free fatty acids. These new data could have a strong impact on the understanding of the physiopathology of obesity. In part, overeating in obesity is due to alteration of the homeostatic feedback created by the peripheral energetic status. Food is a key-point of the hedonic feeding behavior based to the reward system, which has consequences on calories consumption and sensory abilities. In this background, fat taste, altered in obesity for some authors, could be only the consequence of overweight. Fat taste could be modified by the feeding behavior and the body composition, because of alteration of the reward system involved into the acceptation of the palatable energy-rich foods such as lipids or carbohydrates. Alteration of the reward system should be taken into account in the physiopathology of obesity, and offers promising prospects about diagnosis and future treatment of obesity

Le goût : physiologie, rôles et dysfonctionnements

Article de vulgarisationNational audienceThe sense of taste involves multimodal sensory activation to detect and identify many flavors. Today, five primary tastes have been identified (sweet, salt, sour, bitter and umami). These are often combined to form complex tastes. The physiology of gustatory pathways is complex. The activation of gustatory receptors located in the mouth leads to an ascendant pathway through the neurons of the solitary nucleus in the brainstem and the neurons located in the thalamus. After the thalamus, the gustative signal modulates the ipsilateral primary taste cortex and then the secondary taste area. The secondary taste cortex, which combines representations of taste and smell, allows cortical processing and the convergence of the different sensory pathways. The other sensory modalities, such as somatosensory, olfactory, visual and hearing modalities, also interact with gustation at different stages of gustative integration. The sense of taste has three main roles: to detect and identify foods that can be eaten, to provide information in the decision to ingest or reject the food, and to trigger the digestion, absorption and storage of food. Taste problems are frequent and not diagnosed often enough. If physicians do not take them into account, they can worsen the underlying disease by causing malnutrition. Many drugs and diseases can cause gustatory loss. The underlying mechanisms are various and often unknown. Increasing our knowledge of taste physiology could improve our understanding of taste pathology. The main aim is to treat taste problems in order to avoid malnutrition and aggravation of the underlying disease.Parmi les cinq sens, le goût correspond à une activation sensorielle multimodale permettant de détecter et d’identifier de nombreux stimuli que sont les saveurs. Il existe actuellement cinq saveurs primaires (sucré, salé, acide, amer, umami) qui peuvent se combiner entre elles pour former des sensations gustatives plus élaborées. La physiologie de la gustation est complexe. Les substances sapides contenues dans les aliments activent les récepteurs gustatifs situés dans les bourgeons du goût. Les cellules gustatives ainsi stimulées transmettent le signal au cortex gustatif primaire ipsilatéral. Les aires corticales secondaires, communes aux sensations olfactives et gustatives, permettent ensuite l’intégration des informations sensorielles. Les autres sensibilités (la somesthésie avec la sensibilité trigéminale, l’olfaction, la vision et l’audition) interagissent avec la gustation. Trois rôles principaux sont attribués au goût : la détection et l’identification des aliments, le rejet ou l’acceptation de l’aliment grâce à la composante hédonique des sensations et enfin, la préparation de la digestion, de l’absorption et du stockage des nutriments. En pathologie, les altérations du goût sont fréquentes, bien que sous-diagnostiquées, et peuvent aggraver la maladie sous-jacente en induisant une dénutrition. Des anomalies du goût peuvent être induites par de nombreuses pathologies ou des médicaments. Les mécanismes responsables varient en fonction de la pathologie et sont souvent mal connus. L’amélioration des connaissances des mécanismes physiologiques qui sous-tendent la gustation permettra de mieux comprendre les altérations du « goût » en pathologie pour tenter d’y faire face chez les patients à risque de dénutrition

Dynamique et contrôle d'une paire de tourbillons en effet de sol

International audienceThe dynamics and control of a vortex pair in ground effect are investigated ina planar, incompressible and laminar setting. The evolution of the vortices obtained numerically shows vortex rebound as a consequence of the separation of the boundary layer induced at the wall by the vortices. An optimal control approach is developed and employed for vortex Reynolds numbers of 200 and 1000 in order to identify the optimal Dirichlet boundary condition at the wall to counteract this rebound and allow for an increased lateral displacement of the vortex, similarly to the inviscid evolution of the flow, which features hyperbolic trajectories. The work is primarily a conceptual approach to deal with aircraft separation distances in airport airspace by moving the vortices laterally, away from the runway but may also apply to the control of coherent structures in wall bounded turbulence. The most efficient control is able to double the lateral position and yields mostly vertical in and outflow at the wall. An optimal horizon time is found, equal to 5 characteristic time units of the vortex system, beyond which control is not able to further displace the vortices. The control is shown to delay the separation of the boundary layer at the origin of vortex rebound by applying suction ahead of the vortex, and to generate a vorticity flux at the wall, leading to a pusher vortex of sign opposite to that of the primary vortex, that attenuates the effect of the no-slip boundary condition at the wall by pushing the vortex outward.La dynamique et le contrôle d'une paire de tourbillons en effet de sol sont étudiés dans un cadre plan, incompressible et laminaire. L'évolution des tourbillons obtenus montre le rebond du tourbillon à la suite de la séparation de la couche induite au sol par ces tourbillons. Une approche de contrôle optimale est développée et utilisée pour des nombres de Reynolds entre 200 et 1000 afin d'identifier la condition limite optimale au sol pour contrer ce rebond et permettre un déplacement latéral accru du tourbillon, de la même manière que l'évolution inviscide de l'écoulement, qui présente des trajectoires hyperboliques. Le travail est principalement une approche conceptuelle pour gérer les distances de séparation des aéronefs dans l'espace aérien de l'aéroport en déplaçant les tourbillons latéralement, loin de la piste, mais peut également s'appliquer à la contrôle des structures cohérentes dans une turbulence de paroi. Le contrôle le plus efficace est en mesure de doubler la position latérale et donne principalement des vitesses au sol verticales. On trouve un temps d'horizon optimal égal à 5 unités de temps caractéristiques du système tourbillonnaire, au-delà duquel le contrôle n'est pas en mesure de déplacer davantage les tourbillons. Il est démontré que le contrôle retarde la séparation de la couche limite à l'origine du tourbillon rebond en appliquant une succion en avant du tourbillon, et qui génère un flux de vorticité à la paroi, menant à un tourbillon "repoussoir" de signe opposé à celui du tourbillon primaire. Ce dernier atténue l'effet de la condition aux limites d'adhérence à la paroi en "poussant" le tourbillon vers l'extérieur

potentiels évoqués gustatifs en réponse à une stimulation intermittente de saccharose

National audienc

Gustatory evoked cortical activity in humans in response to saccharin stimuli

National audienceIntroduction/Objectives: Gustatory Evoked Potentials (GEP) can be detected in response to an intermittent stimulation of the gustatory receptors by a primary flavour. Contrary the other evoked cortical potentials (visual, auditory or sensory), GEP have not been extensively studied due to their recording heterogeneity. Our aim was to establish a reliable recording of GEP in Humans. Methods: Voluntary and healthy subjects were included in this experiment. A saccharin solution with several concentrations (5, 10 or 20g per 100mL) was used as the gustatory stimulus. Each session was performed on a different day, with an interval of at least 2 hours after eating or drinking. Control session was performed using water or no stimulus. The saccharin solution was presented to the median part of the tongue by intermittent stimulation. The intermittent stimuli were monitored by a specific equipment built for this purpose. Each 1s stimulus was presented 20 times with an inter-stimulus interval of 1min water. Each session was repeated twice. GEP were recorded from 9 cortical sites with EEG sensors: Cz, Fz, Pz, C3, C4, F3, F4, Fp1 and Fp2 of the 10/20 system (referenced against linked earlobes). GEP were obtained after average of all the responses. Results: Fifteen healthy subjects participated in this experiment: 10 women and 5 men, from 25 to 63 years old (mean age 34). GEP consisted in one negative wave, without differences between men and women: their latency varied from 140 to 181ms and their amplitude fluctuated from 7 to 24µV. There is a good inter- and intra-individual reproducibility. None GEP was obtained during the control sessions. The others experiments (stimuli by different saccharin concentrations) are in progress. Discussion/Conclusion: These data demonstrate that record GEP in Humans in response to saccharin stimuli is reliable. These data are in good agreement with the previous works. Studies are currently conducted to assess GE cortical activity in response to other primary flavor and to determine the effect of satiety on these parameters

COVID 19-Induced Smell and Taste Impairments: Putative Impact on Physiology

International audienceSmell and taste impairments are recognized as common symptoms in COVID 19 patients even in an asymptomatic phase. Indeed, depending on the country, in up to 85-90% of cases anosmia and dysgeusia are reported. We will review briefly the main mechanisms involved in the physiology of olfaction and taste focusing on receptors and transduction as well as the main neuroanatomical pathways. Then we will examine the current evidences, even if still fragmented and unsystematic, explaining the disturbances and mode of action of the virus at the level of the nasal and oral cavities. We will focus on its impact on the peripheral and central nervous system. Finally, considering the role of smell and taste in numerous physiological functions, especially in ingestive behavior, we will discuss the consequences on the physiology of the patients as well as management regarding food intake