fMRI Supports the Sensorimotor Theory of Motor Resonance

The neural mechanisms mediating the activation of the motor system during action observation, also known as motor resonance, are of major interest to the field of motor control. It has been proposed that motor resonance develops in infants through Hebbian plasticity of pathways connecting sensory and motor regions that fire simultaneously during imitation or self movement observation. A fundamental problem when testing this theory in adults is that most experimental paradigms involve actions that have been overpracticed throughout life. Here, we directly tested the sensorimotor theory of motor resonance by creating new visuomotor representations using abstract stimuli (motor symbols) and identifying the neural networks recruited through fMRI. We predicted that the network recruited during action observation and execution would overlap with that recruited during observation of new motor symbols. Our results indicate that a network consisting of premotor and posterior parietal cortex, the supplementary motor area, the inferior frontal gyrus and cerebellum was activated both by new motor symbols and by direct observation of the corresponding action. This tight spatial overlap underscores the importance of sensorimotor learning for motor resonance and further indicates that the physical characteristics of the perceived stimulus are irrelevant to the evoked response in the observer

CD16 Expression on Monocytes in Healthy Individuals but Not Schistosome-Infected Patients Is Positively Associated with Levels of Parasite-Specific IgG and IgG1

Human IgG1 antibody responses are associated with protection against Schistosoma haematobium infection and are now a target for schistosome vaccine development. This study aimed to investigate the relationship between total IgG and the IgG subclasses and the monocyte IgG receptor, known as FcγRIIIa or CD16, in schistosome exposed people. Systemic levels of schistosome-specific anti-adult worm total IgG and IgG subclass titres were measured by ELISA in 100 individuals from an S. haematobium endemic area in Zimbabwe and, using parametric statistical methods and regression analysis, related to the levels of CD16 expression on individuals' circulating monocytes, determined via flow cytometry. Monocyte CD16 expression rose with parasite-specific total IgG and IgG1 in healthy participants, but not in schistosome infected patients. Similar to parasite-specific IgG and IgG1, CD16 expression in healthy individuals is associated with protection against schistosome infection. This relationship indicates a mechanistic link between the innate and adaptive immune responses to helminth infection in protection against infection. Further understanding the elements of a protective immune response in schistosomiasis may aid in efforts to develop a protective vaccine against this disease.This work was supported by the World Health Organisation and the Wellcome Trust grant WT082028MA, the Thrasher Research Fund and the Medical Research Council grant LJA-544

The ‘affect tagging and consolidation’ (ATaC) model of depression vulnerability

Since the 1960’s polysomnographic sleep research has demonstrated that depressive episodes are associated with REM sleep alterations. Some of these alterations, such as increased REM sleep density, have also been observed in first-degree relatives of patients and remitted patients, suggesting that they may be vulnerability markers of major depressive disorder (MDD), rather than mere epiphenomena of the disorder. Neuroimaging studies have revealed that depression is also associated with heightened amygdala reactivity to negative emotional stimuli, which may also be a vulnerability marker for MDD. Several models have been developed to explain the respective roles of REM sleep alterations and negatively-biased amygdala activity in the pathology of MDD, however the possible interaction between these two potential risk-factors remains uncharted. This paper reviews the roles of the amygdala and REM sleep in the encoding and consolidation of negative emotional memories, respectively. We present our ‘affect tagging and consolidation’ (ATaC) model, which argues that increased REM sleep density and negatively-biased amygdala activity are two separate, genetically influenced risk-factors for depression which interact to promote the development of negative memory bias – a well-known cognitive vulnerability marker for depression. Predictions of the ATaC model may motivate research aimed at improving our understanding of sleep dependent memory consolidation in depression aetiology

Le cortex préfrontal et la dopamine striatale dans l'apprentissage guidé par la récompense : conception et étude d'une tâche cognitive d'exploration par essais et erreurs en imagerie par résonance magnétique fonctionnelle et en tomographie par émission de positons avec le 11C-raclopride

Models of executive control and prefrontal cortex give a growing importance to reward signals in decision-making. Dopamine could play a key role in signalling the difference between obtained and expected reward (reward prediction error). We combined psychophysics, functional magnetic resonance imaging (fMRI), and positron emission tomography (PET) with a dopaminergic D2/D3 receptor antagonist (11C-raclopride) in order to study the neural bases of reinforcement learning of a motor sequence in human. fMRI allowed us to track the dynamics of this mental effort, which implied a large bilateral prefrontal, parietal and striatal network that activated suddenly during trial and error learning periods and collapsed during ensuing routinized repetition periods. This collapse could be driven by an elementary deduction process that predated the actual reception of reward (autoevaluation).Moreover, some regions of that network were particularly engaged in processing statistical parameters of reward (the reward prediction error and the quantity of information).At the same time, we developed a recent method of dynamical evaluation of dopamine release in vivo using PET. We showed that dopamine release increased bilaterally in ventral striatum and caudate nucleus during periods of trial and error search of motor sequences. In order to validate these observations and to evaluate the sensitivity of that method, we employed a standard PET paradigm (measure of raclopride binding potential).This paradigm also allowed us to measure a correlation between dopamine release in the right ventral striatum and subjects' behavioural values. These results are in line with the hypothesis of a role of the striatal dopamine in reinforcement learning in humans.Thus, for the first time, the combination of fRMI and of dopaminergic receptors labelling with PET allowed us to shed light on both the dynamics of cerebral activation and the “cognitive neurochemistry” involved in a mental effort and reinforcement learning situation.Les modèles du contrôle exécutif et du cortex préfrontal accordent une place grandissante au signal de récompense dans la prise de décision. La dopamine pourrait jouer un rôle clé en signalant l'écart entre la récompense reçue et celle qui était prédite (erreur de prédiction de la récompense).Nous avons combiné les méthodes de psychophysique, d'imagerie par résonance magnétique fonctionnelle (IRMf), et de tomographie par émission de positons (TEP) avec un antagoniste des récepteurs dopaminergiques D2/D3 (11C-raclopride) afin d'étudier chez l'homme les mécanismes de l'apprentissage d'une séquence motrice guidé par la récompense. L'IRMf nous a permis d'analyser en détail la dynamique de cet effort mental, impliquant un réseau préfrontal, pariétal et striatal distribué qui s'activait rapidement durant les périodes de recherche de séquences par essais et erreurs et s'effondrait durant les périodes suivantes de répétition routinière. Cet effondrement pouvait être conduit par un processus de déduction élémentaire préalable à la réception de la récompense (autoévaluation).De plus, certaines sous-régions de ce réseau étaient particulièrement engagées dans le traitement de paramètres statistiques de la récompense (l'erreur de prédiction et la quantité d'information).Parallèlement, nous avons développé une méthode récente d'évaluation dynamique de la libération de dopamine in vivo en TEP, et avons montré que la libération de dopamine augmentait bilatéralement au sein du striatum ventral et du noyau caudé durant la tâche de recherche. Afin de valider ces observations et d'évaluer la sensibilité de cette méthode, nous avons mis en oeuvre un paradigme TEP standard (mesure du « binding potential » du raclopride). Celui-ci nous a en outre permis de mesurer une corrélation entre la libération de dopamine dans le striatum ventral droit et les valeurs comportementales des sujets. Ces résultats sont en accord avec l'hypothèse d'un rôle de la dopamine striatale dans l'apprentissage guidé par la récompense chez l'homme.Pour la première fois à notre connaissance, l'emploi combiné de l'IRMf et du marquage des récepteurs dopaminergiques en TEP nous a ainsi permis de considérer à la fois la dynamique de l'activation cérébrale et la « neurochimie cognitive » dans une situation d'effort mental et d'apprentissage guidés par la récompense

Le cortex préfrontal et la dopamine striatale dans l'apprentissage guidé par la récompense (conception et étude d'une tâche cognitive d'exploration guidée par la récompense en imagerie par résonance magnétique fonctionnelle et en tomographie par émission de positons avec le 11C-raclopride)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Dynamics of prefrontal and cingulate activity during a reward-based logical deduction task.

International audienceWe used behavioral and functional magnetic resonance imaging (fMRI) methods to probe the cerebral organization of a simple logical deduction process. Subjects were engaged in a motor trial-and-error learning task, in which they had to infer the identity of an unknown 4-key code. The design of the task allowed subjects to base their inferences not only on the feedback they received but also on the internal deductions that it afforded (autoevaluation). fMRI analysis revealed a large bilateral parietal, prefrontal, cingulate, and striatal network that activated suddenly during search periods and collapsed during ensuing periods of sequence repetition. Fine-grained analyses of the temporal dynamics of this search network indicated that it operates according to near-optimal rules that include 1) computation of the difference between expected and obtained rewards and 2) anticipatory deductions that predate the actual reception of positive reward. In summary, the dynamics of effortful mental deduction can be tracked with fMRI and relate to a distributed network engaging prefrontal cortex and its interconnected cortical and subcortical regions

Le cenote d'Ani-e-wee(Lifou, Nouvelle-Calédonie) et son gisement exceptionnel de Nautilus macromphalus

International audienceLe cénote d'Ani-e-Wee renferme un gisement exceptionnel des plus anciens nautiles endémiques de Nouvelle-Calédonie. Son étude depuis la mission Namaka en décembre 2011, livre des indices sur l'origine de ces nautiles et sur la formation des karsts de Lifou. Sur 37 spécimens aperçus, 20 coquilles ont été observées et certaines d'entre elles échantillonnées. Elles se situent entre 35m et 40m de profondeur dans l'eau de mer, sous la lentille d'eau douce de surface. La halocline, qui semble limiter le toit du gisement, a été précisée par des mesures physiques et chimiques et corrélée avec les sédiments déposés dans la cavité. Les coquilles montrent par leur état de conservation, leur position et leur datation, que durant plus de 700 ans des nautiles ont fréquenté le cénote depuis la mer et y sont morts piégés. Depuis 6400 ans, vers la fin de la dernière remontée du niveau marin, le milieu karstique les a conservés quasiment intacts, les laissant progressivement se fossiliser. Les résultats de cette première mission apportent également des perspectives d'études des paléoclimats dans cette zone du Pacifique Sud, et de la karstification à Lifou conduite à la fois par la tectonique régionale et par les variations de niveau marin au Pléistocène

Stereotaxic coordinates corresponding to the four conjunctions.

<p>Shown are the stereotaxic coordinates (Talairach and Tournoux (1988), MNI 152 template) for peak voxels, t values (20 conditions in total, having 19 degrees of freedom, leave 77 degrees of freedom from 96 images) and p values for the four conjunctions depicted in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0026859#pone-0026859-g001" target="_blank">Figure 1</a>. Asterisks indicate those regions that were part of the corresponding network but did not appear significant in the conjunction analysis. All <i>p</i> values are corrected for multiple comparisons (Family Wise Error).</p

A Robust Co-Localisation Measurement Utilising Z-Stack Image Intensity Similarities for Biological Studies

Background: Co-localisation is a widely used measurement in immunohistochemical analysis to determine if fluorescently labelled biological entities, such as cells, proteins or molecules share a same location. However the measurement of colocalisation is challenging due to the complex nature of such fluorescent images, especially when multiple focal planes are captured. The current state-of-art co-localisation measurements of 3-dimensional (3D) image stacks are biased by noise and cross-overs from non-consecutive planes. Method: In this study, we have developed Co-localisation Intensity Coefficients (CICs) and Co-localisation Binary Coefficients (CBCs), which uses rich z-stack data from neighbouring focal planes to identify similarities between image intensities of two and potentially more fluorescently-labelled biological entities. This was developed using z-stack images from murine organotypic slice cultures from central nervous system tissue, and two sets of pseudo-data. A large amount of non-specific cross-over situations are excluded using this method. This proposed method is also proven to be robust in recognising colocalisations even when images are polluted with a range of noises. Results: The proposed CBCs and CICs produce robust co-localisation measurements which are easy to interpret, resilient to noise and capable of removing a large amount of false positivity, such as non-specific cross-overs. Performance of this method of measurement is significantly more accurate than existing measurements, as determined statistically usin

Effect of cooling rate on the structural and moisture barrier properties of high and low melting point fats

E-mail [email protected] audienceThe effect of three cooling rates (rapid, intermediate and slow CR) on the moisture barrier properties and on the physical state of acetylated and high melting point hydrophobic self-supported moisture barriers has been investigated. The selected CR were representative of industrial processing conditions and the selected barrier materials of common effective GRAS substances (acetomonopalmitin, white beeswax, two commercial blends of beeswax and acetylated glycerides and a blend of palmitic/stearic acids). Variations of CR affected crystallisation kinetics, SFC in an extend depending on the fat chemical composition and degree of undercooling, crystal size and ratio of polymorphs present in the materials. It did not have major influence on the contact angles with water measured at the surface of the materials and on the mass-volume area properties of the material. The resultant effect on the macroscopic moisture barrier properties of the materials were evaluated using water vapour permeability (WVP) measurements. The CR had no significant effect on the WVP, except for one blend of acetylated fat and beeswax for which a slow CR may have favoured the healing of imperfections. The variations of WVP between all materials and CRs were mainly attributed to variation in materials polarity using multivariable analysi