Les habiletés olfactives des aveugles de naissance : organisation anatomo-fonctionnelle et aspects comportementaux

La littérature décrit certains phénomènes de réorganisation physiologique et fonctionnelle dans le cerveau des aveugles de naissance, notamment en ce qui a trait au traitement de l’information tactile et auditive. Cependant, le système olfactif des aveugles n’a reçu que très peu d’attention de la part des chercheurs. Le but de cette étude est donc de comprendre comment les aveugles traitent l’information olfactive au niveau comportemental et d’investiguer les substrats neuronaux impliqués dans ce processus. Puisque, en règle générale, les aveugles utilisent leurs sens résiduels de façon compensatoire et que le système olfactif est extrêmement plastique, des changements au niveau de l’organisation anatomo-fonctionnelle pourraient en résulter. Par le biais de méthodes psychophysiques et d’imagerie cérébrale (Imagerie par Résonance Magnétique fonctionnelle-IRMf), nous avons investigué les substrats anatomo-fonctionnels sollicités par des stimuli olfactifs. Nous avons trouvé que les aveugles ont un seuil de détection plus bas que les voyants, mais que leur capacité à discriminer et identifier des odeurs est similaire au groupe contrôle. Ils ont aussi plus conscience de l’environnement olfactif. Les résultats d’imagerie révèlent un signal BOLD plus intense dans le cortex orbitofrontal droit, le thalamus, l’hippocampe droit et le cortex occipital lors de l’exécution d’une tâche de détection d’odeur. Nous concluons que les individus aveugles se fient d’avantage à leur sens de l’odorat que les voyants afin d’évoluer dans leur environnement physique et social. Cette étude démontre pour la première fois que le cortex visuel des aveugles peut être recruté par des stimuli olfactifs, ce qui prouve que cette région assume des fonctions multimodales.It is generally acknowledged that people blind from birth develop supra-normal sensory abilities in order to compensate for their visual deficit. While extensive research has been done on the somatosensory and auditory modalities of the blind, information about their sense of smell remains scant. The goal of this study was therefore to understand olfactory processing in the blind at the behavioral and the neuroanatomical levels. Since blind individuals use their remaining senses in a compensatory way to assess their environment and since the olfactory system is highly plastic, it is likely to be susceptible to changes similar to those observed for tactile and auditory modalities. We used psychophysical testing and functional magnetic resonance imaging (fMRI) to investigate the neuronal substrates responsible for odor processing. Our data showed that blind subjects had a lower odor detection threshold compared to the sighted. However, no group differences were found for odor discrimination and odor identification. Interestingly, the OAS revealed that blind participants scored higher for odor awareness. Our fMRI data revealed stronger BOLD responses in the right lateral orbitofrontal cortex, bilateral medio-dorsal thalamus, right hippocampus and left occipital cortex in the blind participants during an odor detection task. We conclude that blind subjects rely more on their sense of smell than the sighted in order to assess their environment and to recognize places and people. This is the first demonstration that the visual cortex of the blind can also be recruited by odorants, thus adding new evidence to its multimodal function

Improving the speckle noise attenuation of simultaneous spectral differential imaging with a focal plane holographic diffuser

Direct exoplanet detection is limited by speckle noise in the point spread function (PSF) of the central star. This noise can be reduced by subtracting PSF images obtained simultaneously in adjacent narrow spectral bands using a multi-channel camera (MCC), but only to a limit imposed by differential optical aberrations in the MCC. To alleviate this problem, we suggest the introduction of a holographic diffuser at the focal plane of the MCC to convert the PSF image into an incoherent illumination scene that is then re-imaged with the MCC. The re-imaging is equivalent to a convolution of the scene with the PSF of each spectral channel of the camera. Optical aberrations in the MCC affect only the convolution kernel of each channel and not the PSF globally, resulting in better correlated images. We report laboratory measurements with a dual channel prototype (1.575 micron and 1.625 micron) to validate this approach. A speckle noise suppression factor of 12-14 was achieved, an improvement by a factor ~5 over that obtained without the holographic diffuser. Simulations of realistic exoplanet populations for three representative target samples show that the increase in speckle noise attenuation achieved in the laboratory would roughly double the number of planets that could be detected with current adaptive optics systems on 8-m telescopes.Comment: 9 pages, 8 figure, to be published in ApJ June 20, 200

Planetary system and star formation science with non-redundant masking on JWST

Non-redundant masking (NRM) is a high contrast high resolution technique that is relevant for future space missions dedicated to either general astrophysics or extrasolar planetary astronomy. NRM mitigates not only atmospheric but instrument-induced speckle noise as well. The recently added mask in the Fine Guidance Sensor Tunable Filter Imager (FGS-TFI) on the James Webb Space Telescope (JWST) will open up a search space between 50 and 400 mas at wavelengths longer than 3.8μm. Contrast of 104 will be achievable in a 10 ks exposure of an M = 7 star, with routine observing, target acquisition, and data calibration methods. NRM places protoplanets in Taurus as well as Jovians younger than 300Myr and more massive than 2MJ orbiting solar type stars within JWST's reach. Stars as bright as M = 3 will also be observable, thus meshing well with next-generation ground-based extreme adaptive optics coronagraphs. This parameter space is inaccessible to both JWST coronagraphs and future 30-m class ground-based telescopes, especially in the mid-IR. We show that NRM used on future space telescopes can deliver unsurpassed image contrast in key niches, while reducing mission risk associated with active primary mirrors

Planetary system and star formation science with non-redundant masking on JWST

Non-redundant masking (NRM) is a high contrast high resolution technique that is relevant for future space missions dedicated to either general astrophysics or extrasolar planetary astronomy. On the ground NRM has opened a rich target space between 0.5 to 4 resolution elements from bright stars. It enabled moderate contrast very high angular resolution observations that have provided dynamical masses for targets beyond the resolution of the Hubble Space Telescope. Such observations challenge the best models of ultra-cool dwarf stars' atmospheres and interiors. The technique succeeds because it sidesteps the effects of speckle noise that plagues direct imaging at moderate Strehl ratios. On a space telescope NRM mitigates instrument-induced speckle noise, thus enabling high contrast even when images are barely diffraction-limited. The non-redundant mask in the Fine Guidance Sensor Tunable Filter Imager (FGS-TFI) on the James Webb Space Telescope (JWST) will open up a search space between 50 and 400 mas at wavelengths longer than 3.8μm. We present simulations that estimate achievable contrast on JWST, and report preliminary results of a testbed experiment using a mask with the same geometry as JWST's. We expect contrast of the order of 104 will be achievable in a 10 ks exposure of an M = 7 star, with observing, target acquisition, and data calibration methods common to the three other imaging instruments on board JWST. As an example of the potential science possible with NRM, we show that if a planet were responsible for clearing the inner 5 AU of the disk around HR8799, it would likely be detectable using JWST FGS-TFI's NRM at 4.6 microns. Stars as bright as M = 3 will also be observable with JWST's NRM, meshing well with next-generation ground-based extreme adaptive optics coronagraphs. JWST NRM's parameter space is inaccessible to both JWST coronagraphs and future 30-m class ground-based telescopes, especially in the mid-IR

Pompéi. Villa de Diomède

Dans la continuité du programme initié en 2013, l’objectif de la deuxième campagne menée sur la Villa de Diomède était de mettre en évidence la chronologie du bâtiment et son rapport aux espaces environnants. Pour ce faire, l’étude archéologique a été centrée sur les façades est et sud de la villa, afin d’éclaircir le rapport à la rue (via delle Tombe) et aux tombes adjacentes. Il convenait d’explorer davantage l’évolution de la villa en fonction des rapports de propriété et d’occupation de l..

Planetary system and star formation science with non-redundant masking on JWST

Non-redundant masking (NRM) is a high contrast high resolution technique that is relevant for future space missions dedicated to either general astrophysics or extrasolar planetary astronomy. NRM mitigates not only atmospheric but instrument-induced speckle noise as well. The recently added mask in the Fine Guidance Sensor Tunable Filter Imager (FGS-TFI) on the James Webb Space Telescope (JWST) will open up a search space between 50 and 400 mas at wavelengths longer than 3.8μm. Contrast of 104 will be achievable in a 10 ks exposure of an M = 7 star, with routine observing, target acquisition, and data calibration methods. NRM places protoplanets in Taurus as well as Jovians younger than 300Myr and more massive than 2MJ orbiting solar type stars within JWST's reach. Stars as bright as M = 3 will also be observable, thus meshing well with next-generation ground-based extreme adaptive optics coronagraphs. This parameter space is inaccessible to both JWST coronagraphs and future 30-m class ground-based telescopes, especially in the mid-IR. We show that NRM used on future space telescopes can deliver unsurpassed image contrast in key niches, while reducing mission risk associated with active primary mirrors

The Hepatokine TSK does not affect brown fat thermogenic capacity, body weight gain, and glucose homeostasis

Objectives Hepatokines are proteins secreted by the liver that impact the functions of the liver and various tissues through autocrine, paracrine, and endocrine signaling. Recently, Tsukushi (TSK) was identified as a new hepatokine that is induced by obesity and cold exposure. It was proposed that TSK controls sympathetic innervation and thermogenesis in brown adipose tissue (BAT) and that loss of TSK protects against diet-induced obesity and improves glucose homeostasis. Here we report the impact of deleting and/or overexpressing TSK on BAT thermogenic capacity, body weight regulation, and glucose homeostasis. Methods We measured the expression of thermogenic genes and markers of BAT innervation and activation in TSK-null and TSK-overexpressing mice. Body weight, body temperature, and parameters of glucose homeostasis were also assessed in the context of TSK loss and overexpression. Results The loss of TSK did not affect the thermogenic activation of BAT. We found that TSK-null mice were not protected against the development of obesity and did not show improvement in glucose tolerance. The overexpression of TSK also failed to modulate thermogenesis, body weight gain, and glucose homeostasis in mice

Planetary system and star formation science with non-redundant masking on JWST

Non-redundant masking (NRM) is a high contrast high resolution technique that is relevant for future space missions dedicated to either general astrophysics or extrasolar planetary astronomy. On the ground NRM has opened a rich target space between 0.5 to 4 resolution elements from bright stars. It enabled moderate contrast very high angular resolution observations that have provided dynamical masses for targets beyond the resolution of the Hubble Space Telescope. Such observations challenge the best models of ultra-cool dwarf stars' atmospheres and interiors. The technique succeeds because it sidesteps the effects of speckle noise that plagues direct imaging at moderate Strehl ratios. On a space telescope NRM mitigates instrument-induced speckle noise, thus enabling high contrast even when images are barely diffraction-limited. The non-redundant mask in the Fine Guidance Sensor Tunable Filter Imager (FGS-TFI) on the James Webb Space Telescope (JWST) will open up a search space between 50 and 400 mas at wavelengths longer than 3.8μm. We present simulations that estimate achievable contrast on JWST, and report preliminary results of a testbed experiment using a mask with the same geometry as JWST's. We expect contrast of the order of 104 will be achievable in a 10 ks exposure of an M = 7 star, with observing, target acquisition, and data calibration methods common to the three other imaging instruments on board JWST. As an example of the potential science possible with NRM, we show that if a planet were responsible for clearing the inner 5 AU of the disk around HR8799, it would likely be detectable using JWST FGS-TFI's NRM at 4.6 microns. Stars as bright as M = 3 will also be observable with JWST's NRM, meshing well with next-generation ground-based extreme adaptive optics coronagraphs. JWST NRM's parameter space is inaccessible to both JWST coronagraphs and future 30-m class ground-based telescopes, especially in the mid-IR

The Near Infrared Imager and Slitless Spectrograph for the James Webb Space Telescope. IV. Aperture Masking Interferometry

The James Webb Space Telescope’s Near Infrared Imager and Slitless Spectrograph (JWST-NIRISS) flies a 7-hole non-redundant mask (NRM), the first such interferometer in space, operating at 3-5 μm wavelengths, and a bright limit of ≃4 mag in W2. We describe the NIRISS Aperture Masking Interferometry (AMI) mode to help potential observers understand its underlying principles, present some sample science cases, explain its operational observing strategies, indicate how AMI proposals can be developed with data simulations, and how AMI data can be analyzed. We also present key results from commissioning AMI. Since the allied Kernel Phase Imaging (KPI) technique benefits from AMI operational strategies, we also cover NIRISS KPI methods and analysis techniques, including a new user-friendly KPI pipeline. The NIRISS KPI bright limit is ≃8 W2 (4.6 μm) magnitudes. AMI NRM and KPI achieve an inner working angle of ∼70 mas, which is well inside the ∼400 mas NIRCam inner working angle for its circular occulter coronagraphs at comparable wavelengths