Saccade learning with concurrent cortical and subcortical basal ganglia loops

The Basal Ganglia is a central structure involved in multiple cortical and subcortical loops. Some of these loops are believed to be responsible for saccade target selection. We study here how the very specific structural relationships of these saccadic loops can affect the ability of learning spatial and feature-based tasks. We propose a model of saccade generation with reinforcement learning capabilities based on our previous basal ganglia and superior colliculus models. It is structured around the interactions of two parallel cortico-basal loops and one tecto-basal loop. The two cortical loops separately deal with spatial and non-spatial information to select targets in a concurrent way. The subcortical loop is used to make the final target selection leading to the production of the saccade. These different loops may work in concert or disturb each other regarding reward maximization. Interactions between these loops and their learning capabilities are tested on different saccade tasks. The results show the ability of this model to correctly learn basic target selection based on different criteria (spatial or not). Moreover the model reproduces and explains training dependent express saccades toward targets based on a spatial criterion. Finally, the model predicts that in absence of prefrontal control, the spatial loop should dominate

Interplay of Kondo effect and strong spin-orbit coupling in multi-hole ultraclean carbon nanotubes

We report on cotunneling spectroscopy magnetoconductance measurements of multi-hole ultraclean carbon nanotube quantum dots in the SU(4) Kondo regime with strong spin-orbit coupling. Successive shells show a gradual weakening of the Kondo effect with respect to the spin-orbital splittings, leading to an evolution from SU(4) to SU(2) symmetry with a suppressed conductance at half shell filling. The extracted energy level spectrum, overally consistent with negligible disorder in the nanotube, shows in the half filled case large renormalizations due to Coulombian effects.Comment: 5 pages, 4 figures, 1 supplementary fil

Design of a biologically inspired navigation system for the Psikharpax rodent robot

This work presents the development and implementation of a biologically inspired navigation system on the autonomous Psikharpax rodent robot. Our system comprises two independent navigation strategies: a taxon expert and a planning expert. The presented navigation system allows the robot to learn the optimal strategy in each situation, by relying upon a strategy selection mechanism

A biologically inspired meta-control navigation system for the Psikharpax rat robot

A biologically inspired navigation system for the mobile rat-like robot named Psikharpax is presented, allowing for self-localization and autonomous navigation in an initially unknown environment. The ability of parts of the model (e. g. the strategy selection mechanism) to reproduce rat behavioral data in various maze tasks has been validated before in simulations. But the capacity of the model to work on a real robot platform had not been tested. This paper presents our work on the implementation on the Psikharpax robot of two independent navigation strategies (a place-based planning strategy and a cue-guided taxon strategy) and a strategy selection meta-controller. We show how our robot can memorize which was the optimal strategy in each situation, by means of a reinforcement learning algorithm. Moreover, a context detector enables the controller to quickly adapt to changes in the environment-recognized as new contexts-and to restore previously acquired strategy preferences when a previously experienced context is recognized. This produces adaptivity closer to rat behavioral performance and constitutes a computational proposition of the role of the rat prefrontal cortex in strategy shifting. Moreover, such a brain-inspired meta-controller may provide an advancement for learning architectures in robotics

Non-native goby species in Switzerland : impacts and management

Non-native invasive species are one of the main reasons for biodiversity decline. They can disrupt ecosystem functioning and cause enormous ecological and economic damage. To manage non-native invasive species is a challenge asking for the cooperation of practice and research. In my thesis, I focus on two recent invaders in the High Rhine, bighead goby (Ponticola kessleri) and round goby (Neogobius melanostomus). These two small bottom-living fish species belong to a group of Ponto-Caspian gobiid species that were introduced probably by ballast water to Europe and North America in the last few decades. In the High Rhine in Basel, they were first detected 2011 and immediately caught the attention of decision makers. Throughout my thesis, I highlight the importance of a transdisciplinary process that can guide researchers in collaboration with decision makers to co-produce measures for an effective and efficient invasive species management. The first step in this transdisciplinary process is to objectively assess priorities and contributions of both scientists and decision makers, followed by an open communication about these priorities and contributions. After such a clarification, ideally, a joint research paradigm for invasive species management can be developed. By applying this process to invasive gobies, several research priorities have emerged in the first step during a workshop together with decision makers: both scientists and decision makers agree that research on management measures such as prevention is of highest priority. A systematic literature review showed that this priority is met by a lack of scientific knowledge on management measures and by an abundance of scientific knowledge on impacts. Scrutinising the scientific knowledge on impacts revealed that the strength and the direction of the impacts strongly depend on local conditions. Thus, the knowledge on impacts in other systems is of limited use if stakeholders want to base their management decisions on expected impacts in their ecosystem of concern, because invasive species’ impacts are ecosystem- and time-dependent. More important is knowledge on preventive management such as e.g. cleaning of boats. If such preventive measures are intended, rapid action should be initiated despite incomplete knowledge about an approaching invader’s impacts. If the preventive approach failed, as is already the case for at least part of the High Rhine, eradication or containment by removing goby eggs and adults can be management alternatives. Using a field study and a population model, I found that eradication is only feasible if started immediately after the introduction of the population and if inflow of new propagules can be stopped. Because measures to control an already established population need an extremely high amount of effort, prevention should be favoured and eradication should only be attempted in very valuable habitats. The findings from my thesis form the basis of a “Goby Action Plan” to implement management measures along the lines of decision makers’ valuation and scientific advice

Interfaces cerveau-ordinateur et rééducation fonctionnelle: étude de cas chez un patient hémiparésique

National audienceLes interfaces cerveau-ordinateur (BCIs: Brain-Computer Interfaces) utilisent l'activité cérébrale d'un individu pour dialoguer avec un ordinateur. L'aide à la communication (outil d'épellation, interface domotique) et la récupération du mouvement (contrôle d'une prothèse ou d'un robot) sont les applications les plus fréquentes des BCIs dans le domaine de l'assistance. L'étude de cas présentée dans cet article montre que les BCIs peuvent également être utilisées dans une approche thérapeutique par neurofeedback pour la rééducation ou la récupération fonctionnelle. Nous décrivons, dans un premier temps, les utilisations thérapeutiques connues des interfaces cerveau-ordinateur. Puis nous présentons une expérience clinique durant laquelle une BCI a été utilisée comme outil d'aide à la rééducation motrice par un patient atteint d'une hémiparésie du côté droit

Determination of citrus fruit origin by using 16S rDNA fingerprinting of bacterial communities by PCR- DGGE : application à la clémentine du Maroc et de l'Espagne

introduction. La consommation des agrumes et de leur jus s'est fortement développée pendant ces dernières décennies. Cependant, à l'heure actuelle, la traçabilité de cette filière est uniquement documentaire. En cas de doute ou de fraude, aucune analyse normalisée ne permet de discriminer ou de déterminer l'origine géographique de la culture du fruit. Matériel et méthodes. Une méthode d'écologie bactérienne, la PCR-DGGE, a été utilisée pour caractériser la flore bactérienne des clémentines importées en France d'Espagne et du Maroc afin de montrer qu'il existe une relation entre les communautés bactériennes des fruits et leurs origines géographiques. Le principe repose sur la détermination de marqueurs biologiques spécifiques d'une localisation donnée. Les protocoles d'extraction et d'amplification des ADN microbiens ont été optimisés. Résultats. Le profil de DGGE étudié par une analyse multivariée a permis de déterminer les profils microbiens spécifiques des différentes régions étudiées. Conclusion. Nous proposons d'utiliser la méthode de la PCR-DGGE comme un nouvel outil de traçabilité qui fournirait un code barres unique aux produits issus d'agrumes et permettrait de relier les agrumes à leur zone de culture originale. (Résumé d'auteur

Differences in gaze anticipation for locomotion with and without vision

International audiencePrevious experimental studies have shown a spontaneous anticipation of locomotor trajectory by the head and gaze direction during human locomotion. This anticipatory behavior could serve several functions: an optimal selection of visual information, for instance through landmarks and optic flow, as well as trajectory planning and motor control. This would imply that anticipation remains in darkness but with different characteristics. We asked 10 participants to walk along two predefined complex trajectories (limaçon and figure eight) without any cue on the trajectory to follow. Two visual conditions were used: (i) in light and (ii) in complete darkness with eyes open. The whole body kinematics were recorded by motion capture, along with the participant's right eye movements. We showed that in darkness and in light, horizontal gaze anticipates the orientation of the head which itself anticipates the trajectory direction. However, the horizontal angular anticipation decreases by a half in darkness for both gaze and head. In both visual conditions we observed an eye nystagmus with similar properties (frequency and amplitude). The main difference comes from the fact that in light, there is a shift of the orientations of the eye nystagmus and the head in the direction of the trajectory. These results suggest that a fundamental function of gaze is to represent self motion, stabilize the perception of space during locomotion, and to simulate the future trajectory, regardless of the vision condition

Instabilité et turbulence dans des écoulements bidimensionnels MHD

We create two-dimensional flows within a thin horizontal mercury layer subjected to a vertical uniform magnetic field. The fluid is set in motion by injecting electrical currents.The first considered flow is a couple of vortices which signs is alternated. We study through visualizations. They reveal the spatial distribution of the velocity field. We calculate the vorticity and stream function by numerical processing of digitized velocity field. These two variables allow us to characterize the encountered stationary vortex structures.Then we turn to a hexagonal network of forced vortex, and we follow the destabilization of this periodic network. We show that even well beyond the transition, destabilized flow is governed by the interaction of nonlinear waves that appeared at times of transition.When disrupting the previous flow on a large scale before the spatial period of the network, a disorganized motion appears. We show that the fluctuating velocity component is quasi homogeneous and isotropic. Velocity fluctuations play an active role in transfers of inertial energy. We check that these transfers are described by the phenomenological laws of two-dimensional turbulence.Nous créons des écoulements bidimensionnels à l’intérieur d’une couche de mercure mince, horizontale et soumise à un champ magnétique uniforme vertical. Le fluide est mis en mouvement en injectant des courants électriques.Le premier type d’écoulements considéré est un couple de tourbillons de signes alternés. Nous l’étudions au moyen de visualisations. Elles révèlent la répartition spatiale du champ de vitesse. Nous calculons la vorticité et la fonction de courant par un traitement numérique du champ de vitesse digitalisé. Ces deux grandeurs nous permettent de caractériser les structures tourbillonnaires stationnaires rencontrées.Nous nous intéressons ensuite à un réseau hexagonal de tourbillons forcé, et suivons la déstabilisation de ce réseau périodique. Nous montrons que même bien au-delà de la transition, l’écoulement déstabilisé est gouverné par les interactions d’ondes non linéaires qui sont apparues aux moments de la transition. Lorsqu’on perturbe l’écoulement précédent à une échelle grande devant la période spatiale du réseau, un mouvement plus désorganisé apparaît. Nous montrons que la composante fluctuante de la vitesse est quasi homogène isotrope. Les fluctuations de la vitesse jouent le rôle actif dans les transferts inertiaux d’énergie. On vérifie que ces transferts sont décrits par les lois phénoménologiques de la turbulence bidimensionnelle