NMDA Receptor Hypofunction Leads to Generalized and Persistent Aberrant γ Oscillations Independent of Hyperlocomotion and the State of Consciousness

International audienceNMDAr antagonists acutely produces, in the rodent CNS, generalized aberrant gamma oscillations, which are not dependent on hyperlocomotion-related brain state or conscious sensorimotor processing. These findings suggest that NMDAr hypofunction-related generalized gamma hypersynchronies represent an aberrant diffuse network noise, a potential electrophysiological correlate of a psychotic-like state. Such generalized noise might cause dysfunction of brain operations, including the impairments in cognition and sensorimotor integration seen in schizophrenia

Functional organisation of cortico-nucleo-olivary loop : influence of Purkinje cells activity

Le cervelet joue un rôle fondamental dans la coordination, l'ajustement, la planification et l'automatisation des mouvements, dans la modulation des réflexes ou encore dans certaines fonctions cognitives. Pour ce faire, il va collecter des informations motrices et sensorielles provenant aussi bien du cortex cérébral que du reste du corps. Ces informations sont relayées vers le cortex et les noyaux cérébelleux via les fibres grimpantes et les fibres moussues. Les fibres grimpantes, projetant depuis l'olive inférieure, convoient des signaux sensori-moteurs impliqués dans certains apprentissages et dans la régulation temporelle des activités cérébelleuses. Ces processus jouent un rôle modulateur de la décharge et des plasticités des cellules de Purkinje. Ces dernières ciblent les noyaux cérébelleux qui représentent l'unique sortie du cervelet. Les efférences de ces noyaux cérébelleux incluent une projection GABAergique dirigée sur l'olive inférieure. Ainsi, les connexions entre l'olive inférieure et le cervelet constituent potentiellement une boucle fermé olivo-cortico-nucléaire. Nos études se basent sur les enregistrements électrophysiologiques in vitro et in vivo de ces trois structures effectués sur un modèle de souris génétiquement modifiées qui permet un contrôle spécifique de la décharge des cellules de Purkinje par l'utilisation de l'optogénétique. La stimulation lumineuse du cortex cérébelleux de ces souris transgéniques active les cellules de Purkinje ainsi que la boucle olivo-cortico-nucléaire sur un délai total d'environ 100 ms. Ces résultats démontrent pour la première fois que les cellules de Purkinje contrôlent de manière phasique leurs afférences olivaires et que ce processus pourrait participer à la régulation des apprentissages moteurs cérébelleux.The cerebellum plays a fundamental role in coordination, adjustment, planning and automation of movements, in the modulation of reflexes and in some cognitive functions. To do this, it will collect motor and sensory information from both the cerebral cortex and the rest of the body. These information are relayed to the cortex and cerebellar nuclei via climbing fibers and mossy fibers. Climbing fibers, the projections from the inferior olive to the cerebellar cortex, carry sensorimotor error and clock signals that trigger motor learning by controlling cerebellar Purkinje cell synaptic plasticity and discharge. Purkinje cells target the deep cerebellar nuclei, which are the output of the cerebellum and include an inhibitory GABAergic projection to the inferior olive. This pathway identifies a potential closed loop in the olivo-cortico-nuclear network. Therefore, sets of Purkinje cells may phasically control their own climbing fiber afferents. Here, using in vitro and in vivo recordings, we describe a genetically modified mouse model that allows the specific optogenetic control of Purkinje cell discharge. Tetrode recordings in the cerebellar nuclei demonstrate that focal stimulations of Purkinje cells strongly inhibit spatially restricted sets of cerebellar nuclear neurons. Strikingly, such stimulations trigger delayed climbing-fiber input signals in the stimulated Purkinje cells. Therefore, our results demonstrate that Purkinje cells phasically control the discharge of their own olivary afferents and thus might participate in the regulation of cerebellar motor learning

Functional organisation of cortico-nucleo-olivary loop : influence of Purkinje cells activity

Le cervelet joue un rôle fondamental dans la coordination, l'ajustement, la planification et l'automatisation des mouvements, dans la modulation des réflexes ou encore dans certaines fonctions cognitives. Pour ce faire, il va collecter des informations motrices et sensorielles provenant aussi bien du cortex cérébral que du reste du corps. Ces informations sont relayées vers le cortex et les noyaux cérébelleux via les fibres grimpantes et les fibres moussues. Les fibres grimpantes, projetant depuis l'olive inférieure, convoient des signaux sensori-moteurs impliqués dans certains apprentissages et dans la régulation temporelle des activités cérébelleuses. Ces processus jouent un rôle modulateur de la décharge et des plasticités des cellules de Purkinje. Ces dernières ciblent les noyaux cérébelleux qui représentent l'unique sortie du cervelet. Les efférences de ces noyaux cérébelleux incluent une projection GABAergique dirigée sur l'olive inférieure. Ainsi, les connexions entre l'olive inférieure et le cervelet constituent potentiellement une boucle fermé olivo-cortico-nucléaire. Nos études se basent sur les enregistrements électrophysiologiques in vitro et in vivo de ces trois structures effectués sur un modèle de souris génétiquement modifiées qui permet un contrôle spécifique de la décharge des cellules de Purkinje par l'utilisation de l'optogénétique. La stimulation lumineuse du cortex cérébelleux de ces souris transgéniques active les cellules de Purkinje ainsi que la boucle olivo-cortico-nucléaire sur un délai total d'environ 100 ms. Ces résultats démontrent pour la première fois que les cellules de Purkinje contrôlent de manière phasique leurs afférences olivaires et que ce processus pourrait participer à la régulation des apprentissages moteurs cérébelleux.The cerebellum plays a fundamental role in coordination, adjustment, planning and automation of movements, in the modulation of reflexes and in some cognitive functions. To do this, it will collect motor and sensory information from both the cerebral cortex and the rest of the body. These information are relayed to the cortex and cerebellar nuclei via climbing fibers and mossy fibers. Climbing fibers, the projections from the inferior olive to the cerebellar cortex, carry sensorimotor error and clock signals that trigger motor learning by controlling cerebellar Purkinje cell synaptic plasticity and discharge. Purkinje cells target the deep cerebellar nuclei, which are the output of the cerebellum and include an inhibitory GABAergic projection to the inferior olive. This pathway identifies a potential closed loop in the olivo-cortico-nuclear network. Therefore, sets of Purkinje cells may phasically control their own climbing fiber afferents. Here, using in vitro and in vivo recordings, we describe a genetically modified mouse model that allows the specific optogenetic control of Purkinje cell discharge. Tetrode recordings in the cerebellar nuclei demonstrate that focal stimulations of Purkinje cells strongly inhibit spatially restricted sets of cerebellar nuclear neurons. Strikingly, such stimulations trigger delayed climbing-fiber input signals in the stimulated Purkinje cells. Therefore, our results demonstrate that Purkinje cells phasically control the discharge of their own olivary afferents and thus might participate in the regulation of cerebellar motor learning

Organisation fonctionnelle de la boucle olivo-cortico-nucléaire : influence de l'activité des cellules de Purkinje

The cerebellum plays a fundamental role in coordination, adjustment, planning and automation of movements, in the modulation of reflexes and in some cognitive functions. To do this, it will collect motor and sensory information from both the cerebral cortex and the rest of the body. These information are relayed to the cortex and cerebellar nuclei via climbing fibers and mossy fibers. Climbing fibers, the projections from the inferior olive to the cerebellar cortex, carry sensorimotor error and clock signals that trigger motor learning by controlling cerebellar Purkinje cell synaptic plasticity and discharge. Purkinje cells target the deep cerebellar nuclei, which are the output of the cerebellum and include an inhibitory GABAergic projection to the inferior olive. This pathway identifies a potential closed loop in the olivo-cortico-nuclear network. Therefore, sets of Purkinje cells may phasically control their own climbing fiber afferents. Here, using in vitro and in vivo recordings, we describe a genetically modified mouse model that allows the specific optogenetic control of Purkinje cell discharge. Tetrode recordings in the cerebellar nuclei demonstrate that focal stimulations of Purkinje cells strongly inhibit spatially restricted sets of cerebellar nuclear neurons. Strikingly, such stimulations trigger delayed climbing-fiber input signals in the stimulated Purkinje cells. Therefore, our results demonstrate that Purkinje cells phasically control the discharge of their own olivary afferents and thus might participate in the regulation of cerebellar motor learning.Le cervelet joue un rôle fondamental dans la coordination, l'ajustement, la planification et l'automatisation des mouvements, dans la modulation des réflexes ou encore dans certaines fonctions cognitives. Pour ce faire, il va collecter des informations motrices et sensorielles provenant aussi bien du cortex cérébral que du reste du corps. Ces informations sont relayées vers le cortex et les noyaux cérébelleux via les fibres grimpantes et les fibres moussues. Les fibres grimpantes, projetant depuis l'olive inférieure, convoient des signaux sensori-moteurs impliqués dans certains apprentissages et dans la régulation temporelle des activités cérébelleuses. Ces processus jouent un rôle modulateur de la décharge et des plasticités des cellules de Purkinje. Ces dernières ciblent les noyaux cérébelleux qui représentent l'unique sortie du cervelet. Les efférences de ces noyaux cérébelleux incluent une projection GABAergique dirigée sur l'olive inférieure. Ainsi, les connexions entre l'olive inférieure et le cervelet constituent potentiellement une boucle fermé olivo-cortico-nucléaire. Nos études se basent sur les enregistrements électrophysiologiques in vitro et in vivo de ces trois structures effectués sur un modèle de souris génétiquement modifiées qui permet un contrôle spécifique de la décharge des cellules de Purkinje par l'utilisation de l'optogénétique. La stimulation lumineuse du cortex cérébelleux de ces souris transgéniques active les cellules de Purkinje ainsi que la boucle olivo-cortico-nucléaire sur un délai total d'environ 100 ms. Ces résultats démontrent pour la première fois que les cellules de Purkinje contrôlent de manière phasique leurs afférences olivaires et que ce processus pourrait participer à la régulation des apprentissages moteurs cérébelleux

Aerobic and anaerobic glucose metabolism of Phytomonas sp. isolated from Euphorbia characias

Metabolic studies on Phytomonas sp. isolated from the lactiferous tubes of the latex-bearing spurge Euphorbia characias indicate that glucose is the preferred energy and carbon substrate during logarithmic growth. In stationary phase cells glucose consumption was dramatically reduced. Glucose consumption and end-product formation were measured on logarithmically growing cells, both under aerobic (air and 95% O2/5% CO2) and anaerobic (95% N2/5% CO2 and 100% N2) conditions. The rate of glucose consumption slightly increased under anaerobic conditions indicating that Phytomonas lacks a 'reverse Pasteur' effect contrary to the situation encountered in Leishmania major. Major end-products of glucose catabolism under aerobic conditions, detected by enzymatic and NMR measurements, were acetate, ethanol and carbon dioxide and under anaerobic conditions ethanol, glycerol and carbon dioxide. Smaller amounts of pyruvate, succinate, L-malate, L-lactate, phosphoenolpyruvate, alanine and aspartate were also detected

A compact kinetic inductance travelling wave parametric amplifier with continuous periodic loading structure

International audienceTravelling wave parametric amplifiers (TWPAs) made from highly non-linear reactive superconducting thin films have been demonstrated to be a potentially viable quantum-noise-limited amplifier technology for various fundamental physics platforms, including microwave/mm/sub-mm astronomy, dark matter search experiments, neutrino mass experiments, and qubit readout. We present a kinetic inductance TWPA consisting of a patterned titanium nitride film on a sapphire substrate, which comprises a coplanar waveguide (CPW) with a continuous, smoothed periodic loading (PL) structure that modulates the characteristic impedance of the CPW in a double sinusoidal fashion. This double sinusoidal modulation creates much stronger dispersion features than a conventional PL design, which allows for phase matching and pump harmonic suppression over a much shorter transmission length, potentially leading to reduced losses. In this paper, we shall discuss in detail the design of our TWPA and present the predicted gain-bandwidth characteristics from electromagnetic simulations

Preliminary characterisation of titanium nitride thin film at 300 mK for the development of kinetic inductance travelling wave parametric amplifiers

International audienceTravelling wave parametric amplifiers (TWPAs) made from highly nonlinear reactive superconducting thin films have been demonstrated to be a viable technology for various quantum applications, including fundamental physics experiments such as astronomy and axion dark matter searches, as well as commercial applications like quantum computational and communication systems. In this paper, we present the design of a kinetic inductance TWPA comprising a patterned titanium nitride film that can operate at 0.3K to demonstrate the feasibility of operation closer to 1K temperature, paving the way to achieve even higher bath temperature operation. We discuss in detail the design of our TWPA, along with the predicted gain-bandwidth product and other characteristics. We perform the preliminary experimental investigation of the thin film properties and compare that with the simulated results. We found that there are several discrepancies between the measured and the predicted behaviour of the thin film. We attribute these differences to the fact that the fabricated thin film has a different gap voltage, resistivity and thickness to what we expected. With a new set of estimated parameters, we successfully reproduce the measured transmission profile. We further show that by utilising bridges to ensure equipotential grounds for the CPW lines, we are able to reduce the rippling effect and achieve a higher gain with broader bandwidth. We expect that our TWPA can achieve higher than 20 dB gain from approximately 0-8 GHz

Engineering the thin film characteristics for optimal performance of superconducting kinetic inductance amplifiers using a rigorous modelling technique

Background: Kinetic Inductance Travelling Wave Parametric Amplifiers (KITWPAs) are a new variant of superconducting amplifier that can potentially achieve high gain with quantum-limited noise performance over broad bandwidth, which is important for many ultra-sensitive experiments. In this paper, we present a novel modelling technique that can better capture the electromagnetic behaviour of a KITWPA without the translation symmetry assumption, allowing us to flexibly explore the use of more complex transmission line structures and better predict their performance. Methods: In order to design a KITWPA with optimal performance, we investigate the use of different superconducting thin film materials, and compare their pros and cons in forming a high-gain low-loss medium feasible for amplification. We establish that if the film thickness can be controlled precisely, the material used has less impact on the performance of the device, as long as it is topologically defect-free and operating within its superconducting regime. With this insight, we propose the use of Titanium Nitride (TiN) film for our KITWPA as its critical temperature can be easily altered to suit our applications. We further investigate the topological effect of different commonly used superconducting transmission line structures with the TiN film, including the effect of various non-conducting materials required to form the amplifier. Results: Both of these comprehensive studies led us to two configurations of the KITWPA: 1) A low-loss 100 nm thick TiN coplanar waveguide amplifier, and 2) A compact 50 nm TiN inverted microstrip amplifier. We utilise the novel modelling technique described in the first part of the paper to explore and investigate the optimal design and operational setup required to achieve high gain with the broadest bandwidth for both KITWPAs, including the effect of loss. Conclusions: Finally, we conclude the paper with the actual layout and the predicted gain-bandwidth product of our KITWPAs

Going Up the Ladder: Stacking Four 4,4′-Bipyridine Moieties within a Ti(IV)-Based Tetranuclear Architecture

Biphenol-based ligands have proven their ability to bind titanium(IV) centers and generate sophisticated self-assembled structures in which auxiliary nitrogen ligands often complete the coordination sphere of the metal and improve stability. Here, a central 4,4′-bipyridine, which acts as both a spacer and a source of monodentate nitrogen to complete the coordination sphere of the Ti(IV) complex, was incorporated within two bis-2,2′-biphenol strands, 3H4 and 4H4. Both proligands possess structural features that are well adapted to form self-assembled structures built from titanium–oxygen–nitrogen units; however, their different degrees of torsional freedom strongly influenced the nuclearity of the complexes formed. The presence of a phenyl spacer between the bipyridine and the biphenol moieties of 3H4 provided enough flexibility for the ligand to wrap around one titanium(IV) center to form a mononuclear complex Ti(3)(DMF)2 in the presence of dimethylformamide (DMF). Assembly of the more rigid ligand 4H4 with Ti(OiPr)4 afforded a tetranuclear complex Ti4(4)2(4H)2(OEt)2 containing four stacked 4,4′-bipyridine units as shown by the X-ray structure of the complex. Density functional theory studies suggested that the assembly of this tetrametallic complex involves a dimetallic intermediate with TiO6 nodes that is converted to the thermodynamically stable tetranuclear complex with two TiO6 nodes and two TiO5N units with enhanced covalent character