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Background. Repetitive and restricted behaviors and interests (RRBI) are core symptoms of autism with a complex entity and are commonly categorized into ‘motor-driven’ and ‘cognitively-driven’. RRBI symptomatology depends on the individual’s clinical environment limiting the understanding of RRBI physiology, particularly their associated neuroanatomical structures. The complex RRBI heterogeneity needs to explore the whole RRBI spectrum by integrating the clinical context (autistic individuals, their relatives and typical developing (TD) individuals). We hypothesized that different RRBI dimensions would emerge by exploring the whole spectrum of RRBI, and that these dimensions are associated with neuroanatomical signatures - involving cortical & subcortical areas. Method. A sample of 792 individuals composed of 267 autistic subjects, their 370 first-degree relatives and 155 TD individuals was enrolled in the study. We assessed the whole patterns of RRBI in each individual by using the Repetitive Behavior Scale-Revised and the Yale-Brown Obsessive Compulsive Scale. We estimated brain volumes using MRI scanner for a subsample of the subjects (n=152, 42 ASD, 89 relatives and 13 TD). We first investigated the dimensionality of RRBI by performing a principal component analysis on all items of these scales and included all the sampling population. We then explored the relationship between RRBI-derived factors with brain volumes using linear regression models. Results. We identified 3 main factors (with 30.3% of the RRBI cumulative variance): Factor 1 (FA1, 12.7%) reflected mainly the ‘motor-driven’ RRBI symptoms; Factor 2 and 3 (respectively 8.8% and 7.9%) gathered mainly Y-BOCS related items and represented the ‘cognitively-driven’ RRBI symptoms. These three factors were significantly associated with the right/left putamen volumes but with opposite effects: FA1 was negatively associated with an increased volume of the right/left putamen conversely to FA2 & FA3 (all uncorrected pConclusion. Our results suggested 3 coherent RRBI dimensions involving the putamen commonly and other structures according to the RRBI dimension. The exploration of the putamen’s integrative role in RSBI needs to be strengthened in further studies.

Background Autism spectrum disorders (ASD) are neurodevelopmental disorders characterised by deficits in social communication or interaction and repetitive behaviours. Maternal immune activation (MIA) during the mid-pregnancy is a known risk factor for ASD. Although reported in 15% of affected individuals, little is known about the specificity of their clinical profiles. Adaptive skills represent a holistic approach to a person's competencies and reflect specifically in autism, their strengths and difficulties. Methods In this study, we hypothesised that individual with ASD with a history of MIA (MIA+) could be more severely socio-adaptively impaired than those without MIA during pregnancy (MIA−). To answer this question, we considered two independent cohorts of individuals with ASD (PARIS study and FACE ASD) screened for pregnancy history, and used a supervised and unsupervised statistical approach. Results We included 295 mother-child dyads with 14% of them with MIA+. We found that ASD-MIA+ individuals displayed more severe maladaptive behaviors, specifically in their socialization abilities. MIA+ directly influenced individual's socio-adaptive skills, independent of other covariates, including ASD severity. Interestingly, MIA+ may affected persistently the socio-adaptive behavioral trajectories of individuals with ASD. Limitations : The current study has a retrospective design with possible recall bias regarding the MIA event and, even if pooled from two cohorts, has a relatively small population. In addition, we were limited by the number of covariables available potentially impacted socio-adaptive behaviors. Larger prospective study with additional dimensions related to ASD is needed to confirm our results Conclusions Specific pathophysiological pathways may explain these clinical peculiarities of ASD- MIA+ individuals, and may open the way to new perspectives in deciphering the phenotypic complexity of autism and for the development of specific immunomodulatory strategies.

BackgroundExploring neural network dynamics during social interaction could help to identify biomarkers of Autism Spectrum Disorders (ASD). Recently, the cerebellum, a brain structure that plays a key role in social cognition, has attracted growing interest. Here, we investigated the electrophysiological activity of the cortico-cerebrum network during real-time social interaction in ASD. We focused our analysis on theta oscillations (3-8 Hz), which have been associated with large-scale coordination of distant brain areas and might contribute to interoception, motor control, and social event anticipation, all skills known to be altered in ASD.MethodsWe combined the Human Dynamic Clamp, a paradigm for studying realistic social interactions using a virtual avatar, with high-density electroencephalography (HD-EEG). Using source reconstruction, we investigated power in the cortex and the cerebellum, along with coherence between the cerebellum and three cortical areas, and compared our findings in a sample of participants with ASD and with typical development (TD) (n = 140). We developed an open-source pipeline to analyse neural dynamics at the source level from HD-EEG data.ResultsIndividuals with ASD showed a significant increase in theta band power during social interaction compared to resting state, unlike individuals with TD. In particular, we observed a higher theta power over the cerebellum and the frontal and temporal cortices in the ASD group compared to the TD group, alongside bilateral connectivity alterations between the cerebellum and the sensorimotor and parietal cortices.ConclusionsThis study uncovered ASD-specific alterations in the theta dynamics, especially in a network between the cerebellum and social-associated cortical networks.

ImportanceSurveys based on hypothetical situations suggest that health-care providers agree that disclosure of errors and adverse events to patients and families is a professional obligation but do not always disclose them. Disclosure rates and reasons for the choice have not previously been studied.ObjectiveTo measure the proportion of errors disclosed by neonatal intensive care unit (NICU) professionals to parents and identify motives for and barriers to disclosure.DesignProspective, observational study nested in a randomised controlled trial (Study on Preventing Adverse Events in Neonates (SEPREVEN); ClinicalTrials.gov). Event disclosure was not intended to be related to the intervention tested.Setting10 NICUs in France with a 20-month follow-up, starting November 2015.Participantsn=1019 patients with NICU stay ≥2 days with ≥1 error.ExposureCharacteristics of errors (type, severity, timing of discovery), patients and professionals, self-reported motives for disclosure and non-disclosure.Main outcome and measuresRate of error disclosure reported anonymously and voluntarily by physicians and nurses; perceived parental reaction to disclosure.ResultsAmong 1822 errors concerning 1019 patients (mean gestational age: 30.8±4.5 weeks), 752 (41.3%) were disclosed. Independent risk factors for non-disclosure were nighttime discovery of error (OR 2.40; 95% CI 1.75 to 3.30), milder consequence (for moderate consequence: OR 1.85; 95% CI 0.89 to 3.86; no consequence: OR 6.49; 95% CI 2.99 to 14.11), a shorter interval between admission and error, error type and fewer beds. The most frequent reported reasons for non-disclosure were parental absence at its discovery and a perceived lack of serious consequence.Conclusion and relevanceIn the particular context of the SEPREVEN randomised controlled trial of NICUs, staff did not disclose the majority of errors to parents, especially in the absence of moderate consequence for the infant.Trial registration numberNCT02598609.

Background. Sensory processing atypicalities are part of the core symptoms of autism spectrum disorder (ASD) and could result from an excitation/inhibition imbalance. Yet, the convergence level of phenotypic sensory processing atypicalities with genetic alterations in GABA-ergic and glutamatergic pathways remains poorly understood. This study aimed to characterize the distribution of hypo/hyper-sensory profile among individuals with ASD and investigate the role of deleterious mutations in GABAergic and glutamatergic pathways related genes in sensory processing atypicalities. Method. From the Short Sensory Profile (SSP) questionnaire, we defined and explored a score – the differential Short Sensory Profile (dSSP) - as a normalized and centralized hypo/hypersensitivity ratio for 1136 participants (533 with ASD, 210 first-degree relatives, and 267 controls) from two independent study samples (PARIS and LEAP). We also performed an unsupervised item-based clustering analysis on SSP items scores to validate this new categorization in terms of hypo and hyper sensitivity. We then explored the link between the dSSP score and the burden of deleterious mutations in a subset of individuals for which whole-genome sequencing data were available. Results. We observed a mean dSSP score difference between ASD and controls, driven mostly by a high dSSP score variability among groups (PARIS: p2 = 0.0001, LEAP: p2 = 0.02; LEAP: p=0.01, η2 = 0.01). Clusters were similarly characterized by hypo- and hyper-sensitivity items in both study samples (Cramer's V from 0.64 to 0.69, pLimitations. The major limitation was the dSSP score difficulty to discriminate subjects with a similar quantum of hypo- and hyper- sensory symptoms to those with no such symptoms, resulting both in a similar ratio score of 0.Conclusion. The dSSP score could be a relevant clinical score of the hypo/hyper-sensory individual profile in subjects with ASD. Combined with additional sensory domain characteristics, genetics and endophenotypic substrates, the dSSP score will offer new avenues to explore the underlying neurobiological mechanisms of sensory processing atypicalities in ASD.

The paper deals with the optimal control problem that arises when one studies the 4 sphere artificial swimmer at low Reynolds number. Composed of four spheres at the end of extensible arms, the swimmer is known to be able to swim in all directions and orientations in the 3D space. In this paper, optimal strokes, in terms of the energy expended by the swimmer to reach a prescribed net displacement, are fully described in the regime of small strokes. In particular, we introduce a bivector formalism to model the displacements that turns out to be elegant and practical. Numerical simulations are also provided that confirm the theoretical predictions.

To identify quantitative indicators of social communication dysfunctions, we explored the oculomotor performances in subjects with autism spectrum disorders. Discordant findings in the literature have been reported for oculomotor behavior in subjects with autism spectrum disorders. This study aimed to explore reflexive and voluntary saccadic performance in a group of 32 children with autism spectrum disorders (mean age: 12.1 ± 0.5 years) compared to 32 age-, sex-, and IQ-matched typically developing children (control group). We used different types of reflexive and voluntary saccades: gap, step, overlap, and anti-saccades. Eye movements were recorded using an eye tracker (Mobile EBT®) and we measured latency, percentage of anticipatory and express saccades, errors of anti-saccades and gain. Children with autism spectrum disorders reported similar latency values with respect to typically developing children for reflexive and voluntary saccades; in contrast, they made more express and anticipatory saccades overall, as shown in paradigm testing (gap, step, overlap, and anti-saccades). Our findings support previous evidence of the atypicality of the cortical network, which is involved in saccade triggering and attentional processes in children with autism spectrum disorders.

International audience; Repetitive behaviors (RB) represent a wide spectrum of symptoms ranging from sensory-motor stereotypies to complex cognitive rituals, frequently dichotomized as low- and high-order sub-groups of symptoms. Even though these subgroups are considered as phenomenologically distinct in autism spectrum disorder (ASD) and obsessive-compulsive disorder (OCD), brain imaging and genetic studies suggest that they have common mechanisms and pathways. This discrepancy may be explained by the frequent intellectual disability reported in ASD, which blurs the RB expressivity. Given the high heritability of RB, that is, the diversity of symptoms expressed in the relatives are dependent on those expressed in their probands, we hypothesize that if RB expressed in ASD or OCD are two distinct entities, then the RB expressed in relatives will also reflect these two dimensions. We thus conduct a linear discriminant analysis on RB in both the relatives of probands with ASD and OCD and subjects from the general population (n = 1023). The discriminant analysis results in a classification of 81.1% of the controls (p

Early onset anorexia nervosa. Anorexia nervosa is an eating disorder of multifactorial origin. It has a serious physical and psychological impact on the functioning of the individual and the highest risk of mortality from psychiatric disorders. It is defined according to international classifications by a refusal to maintain a normal minimum weight for his age and height, an intense fear of gaining weight and a disturbance of one's body image. This pathology most often affects adolescents but can be diagnosed from the age of 8 years. In this case, it is considered as "early onset anorexia nervosa" or called "prepubescent anorexia nervosa". Its prognosis is serious, and it requires emergency medical care. Multidisciplinary ambulatory care should be favored in the absence of criteria imposing full-time hospitalization. Patient monitoring should continue for several years.Anorexie mentale à début précoce. L’anorexie mentale est un trouble du comportement alimentaire d’origine multifactorielle, grave du fait de son impact physique et psychologique sur le fonctionnement de l’individu et du risque de mortalité le plus élevé des troubles psychiatriques. Elle est définie selon les critères des classifications internationales par un refus de maintenir un poids minimum normal pour son âge et sa taille, une peur intense de prendre du poids et une perturbation de son image corporelle. Cette pathologie touche le plus souvent l’adolescent mais peut être diagnostiquée dès 8 ans. Elle est alors considérée comme survenant « à début précoce » ou dite « anorexie mentale prépubère ». Son pronostic est grave et sa prise en charge est une urgence médicale. Une prise en charge multidisciplinaire ambulatoire est privilégiée en l’absence de critère imposant une hospitalisation à temps complet. Le suivi du patient se poursuivra plusieurs années.

International audience; In everyday life, our activities frequently involve the simultaneous performance of two or more tasks. Sharing attention between two concurrent tasks may result in a decrease in performance specifically among children with neurodevelopmental disorders. The objective of the study was to determine whether the influence of postural conditions (sitting condition, single task; standing condition, dual task) on eye movement performances on three visual tasks with high attentional load (visually-guided saccade task, memory-guided saccade task and fixation task) was different in children with neurodevelopmental disorders (attention deficit and hyperactive disorder, dyslexia, and high functioning autism spectrum disorder) when compared to typically developing children. One hundred and four children (26 per group, sex-age-and IQ-matched groups) were evaluated. We found that for the fixation task only, the three groups of children with neurodevelopmental disorders had poorer eye movements performances in the standing condition compared to the sitting condition while no such difference was found for typically developing children. We suggest that children with neurodevelopmental disorders have fewer attentional resources available for performing correctly oculomotor tasks with high atten-tional load leading to impairment of these tasks for maintaining a good level of postural stability.

International audience; We summarize postural instabilities in children with autistic spectrum disorder (ASD) and in children with attention deficit hyperactivity disorder (ADHD), and we reported behavioral results suggesting poor cerebellar integration. We conclude that postural measures could be a promising method with which to indirectly observe cerebellar performance in children developmental disabilities such as ASD and/or ADHD.

Literature reference for the preprint first posted on medRxiv: https://www.medrxiv.org/content/10.1101/19013771v1; Background: The Human Dynamic Clamp (HDC) is a human-machine interface for studying realistic social interaction under controlled and reproducible conditions. Here, we propose to probe the validity of the HDC as psychometric instrument for quantifying social abilities in children with Autism Spectrum Disorder (ASDs) and neurotypical development. Methods: To study behavioral synchrony, we derived from interaction with the HDC avatar, five standardized scores following a gradient from sensory-motor and motor to higher socio-cognitive skills, in a sample of 155 individuals (113 with ASDs, 42 typically developing participants; aged 5 to 25 years; IQ>70). Results: We conducted regression analyses with normative modeling on global scores according to four sub-conditions (avatar behavior "cooperative/competitive", human task "in-phase/anti-phase", diagnosis and age at inclusion). Children with ASDs tend to have significant lower scores than controls for motor skills. Independently of the phenotype, socio-cognitive skills increase with developmental age, while being affected by the ongoing task and the behavior of the avatar.Discussion: The weaker performance in participants with ASDs for motor skills suggests convergent validity for this score of the HDC during social interaction. Results provide additional evidence of a relationship between sensory-motor and socio-cognitive skills. As we found a significant main effect of age at inclusion, HDC may be used as a marker of aging of socio-cognitive skills during real-time social interaction. Conclusion: Through its standardized and objective evaluation, the HDC not only represents a valid paradigm for the study of interpersonal synchrony but also a clinically relevant psychometric instrument for the evaluation and stratification of socio-motor dysfunctions.

This work investigates the Sparse Cardinal Sine Decomposition (SCSD) method ability to efficiently deal with a Stokes flow about a solid particle immersed in a liquid. In contrat to Alouges and Aussal (Numer Algorithms 70:1–22, 2015), the liquid domain is bounded by a solid and motionless wall. The advocated procedure inverts on the particle and truncated wall boundaries the boundary-integral equation governing the stress there. This is numerically achieved by implementing a Galerkin method. The resulting linear system, with fully-populated and non-symmetric influence matrix, is both compressed and solved by the new SCSD method which allows to accurately deal with a large number of unknowns. Both analytical and numerical comparisons are reported for a spherical particle and several bounded liquid domains. Moreover, the rigid-body motion of spheroidal particles settling in a cylindrical tube is examined.

Detecting where our partners direct their gaze is an important aspect of social interaction. An atypical gaze processing has been reported in autism. However, it remains controversial whether children and adults with autism spectrum disorder interpret indirect gaze direction with typical accuracy. This study investigated whether the detection of gaze direction toward an object is less accurate in autism spectrum disorder. Individuals with autism spectrum disorder (n = 33) and intelligence quotients–matched and age-matched controls (n = 38) were asked to watch a series of synthetic faces looking at objects, and decide which of two objects was looked at. The angle formed by the two possible targets and the face varied following an adaptive procedure, in order to determine individual thresholds. We found that gaze direction detection was less accurate in autism spectrum disorder than in control participants. Our results suggest that the precision of gaze following may be one of the altered processes underlying social interaction difficulties in autism spectrum disorder.

We address the problem of numerical simulation of suspensions of rigid particles in a Stokes flow. We focus on the inclusion of the singular short range interaction effects (lubrication effects) in the simulations when the particles come close one to another. The problem is solved without introducing new hypothesis nor model. As in Lefebvre-Lepot et al. [J. Fluid Mech. 769 (2015) 369–386], the key idea is to decompose the velocity and pressure flows in a sum of a singular and a regular part. In this article, the singular part is computed using an explicit asymptotic expansion of the solution when the distance goes to zero. This expansion is similar to the asymptotic expansion proposed in Hillairet and Kelai [Asymptotic Anal. 95 (2015) 187–241] but is more appropriate for numerical simulations of suspensions. It can be computed for any locally convex (that is the particles have to be convex close to the contact point) and regular shape of particles. Using Hillairet and Kelai [Asymptotic Anal. 95 (2015) 187–241] as an intermediate result, we prove that the remaining part is regular in the sense that it is bounded independently of the distance. As a consequence, only a small number of degrees of freedom are necessary to obtain accurate results. The method is tested in dimension 2 for clusters of two or three aligned particles with general rigid velocities. We show that, as expected, the convergence is independent of the distance.

International audience; Background:Patients with autism have been often reported to have a smaller corpus callosum (CC) than control subjects.; Methods:We conducted a meta-analysis of the literature, analyzed the CC in 694 subjects of the Autism Brain Imaging Data Exchange project, and performed computer simulations to study the effect of different analysis strategies.; Results:Our meta-analysis suggested a group difference in CC size; however, the studies were heavily underpowered (20% power to detect Cohen's d = .3). In contrast, we did not observe significant differences in the Autism Brain Imaging Data Exchange cohort, despite having achieved 99% power. However, we observed that CC scaled nonlinearly with brain volume (BV): large brains had a proportionally smaller CC. Our simulations showed that because of this nonlinearity, CC normalization could not control for eventual BV differences, but using BV as a covariate in a linear model would. We also observed a weaker correlation of IQ and BV in cases compared with control subjects. Our simulations showed that matching populations by IQ could then induce artifactual BV differences.; Conclusions:The lack of statistical power in the previous literature prevents us from establishing the reality of the claims of a smaller CC in autism, and our own analyses did not find any. However, the nonlinear relationship between CC and BV and the different correlation between BV and IQ in cases and control subjects may induce artifactual differences. Overall, our results highlight the necessity for open data sharing to provide a more solid ground for the discovery of neuroimaging biomarkers within the context of the wide human neuroanatomical diversity.

We address the problem of computing the hydrodynamic forces and torques among $N$ solid spherical particles moving with given rotational and translational velocities in Stokes flow. We consider the original fluid–particle model without introducing new hypotheses or models. Our method includes the singular lubrication interactions which may occur when some particles come close to one another. The main new feature is that short-range interactions are propagated to the whole flow, including accurately the many-body lubrication interactions. The method builds on a pre-existing fluid solver and is flexible with respect to the choice of this solver. The error is the error generated by the fluid solver when computing non-singular flows (i.e. with negligible short-range interactions). Therefore, only a small number of degrees of freedom are required and we obtain very accurate simulations within a reasonable computational cost. Our method is closely related to a method proposed by Sangani & Mo (Phys. Fluids, vol. 6, 1994, pp. 1653–1662) but, in contrast with the latter, it does not require parameter tuning. We compare our method with the Stokesian dynamics of Durlofsky et al. (J. Fluid Mech., vol. 180, 1987, pp. 21–49) and show the higher accuracy of the former (both by analysis and by numerical experiments).

The aim of this paper is to propose a new numerical model to simulate 2D vesicles interacting with a newtonian fluid. The inextensible membrane is modeled by a chain of circular rigid particles which are maintained in cohesion by using two different type of forces. First, a spring force is imposed between neighboring particles in the chain. Second, in order to model the bending of the membrane, each triplet of successive particles is submitted to an angular force. Numerical simulations of vesicles in shear flow have been run using Finite Element Method and the FreeFem++[1] software. Exploring different ratios of inner and outer viscosities, we recover the well known "Tank-Treading" and "Tumbling" motions predicted by theory and experiments. Moreover, for the first time, 2D simulations of the "Vacillating-Breathing" regime predicted by theory in [2] and observed experimentally in [3] are done without special ingredient like for example thermal fluctuations used in [4].

International audience; Autism, learning disabilities and attention deficit/hyperactive disorder are often comorbid disorders. In order to try and find some markers that might be transnosographic, we hypothesized that abnormal postural sway profiles may discriminate children with neurodevelopmental disorders (NDDs) from typically developing children. The aim of our study was thus to compare spatial and temporal measures of the Center of Pressure in three distinct groups of children with NDDs (high functioning autism spectrum disorders, learning disabilities (dys-lexia) and attention deficit/hyperactive disorders) and in typically developing children. Postural performances were thus evaluated in 92 children (23 per group, sex-, age-and IQ-matched groups) by using the Multitest Equilibre platform (Framiral ®). Two viewing conditions (eyes open and eyes closed) were tested on a stable and unstable platform. Results reported similar poor postural instability for the three groups of children with NDDs with respect to the typically developing children, and this was observed for both spatial as well as temporal analysis of displacement of the center of pressure. Such postural instability observed in children with NDDs could be due to impairment in using sensorial inputs to eliminate body sway, probably due to poor cerebellar integration.

International audience; In boundary element method (BEM), one encounters linear system with a dense and non-symmetric square matrix which might be so large that inverting the linear system is too prohibitive in terms of cpu time and/or memory. Each usual powerful treatment (Fast Multipole Method, H-matrices) developed to deal with this issue is optimized to efficiently perform matrix vector products. This work presents a new technique to adequately and quickly handle such products: the Sparse Cardinal Sine Decomposition. This approach, recently pioneered for the Laplace and Helmholtz equations, rests on the decomposition of each encountered kernel as series of radial Cardinal Sine functions. Here, we achieve this decomposition for the Stokes problem and implement it in MyBEM, a new fast solver for multi-physical BEM. The reported computational examples permit us to compare the advocated method against a usual BEM in terms of both accuracy and convergence.

A bidimensional simulation of a sphere moving at constant velocity into a cloud of smaller spherical grains without gravity is presented with a non-smooth contact dynamics method. A dense granular “cluster” zone of about constant solid fraction builds progressively around the moving sphere until a stationary regime appears with a constant upstream cluster size that increases with the initial solid fraction ϕ 0 of the cloud. A detailed analysis of the local strain rate and local stress fields inside the cluster reveals that, despite different spatial variations of strain and stresses, the local friction coeffcient μ appears to depend only on the local inertial number I as well as the local solid fraction ϕ , which means that a local rheology does exist in the present non parallel flow. The key point is that the spatial variations of I inside the cluster does not depend on the sphere velocity and explore only a small range between about 10−2 and 10−1 . The influence of sidewalls is then investigated on the flow and the forces.

A bidimensional simulation of a sphere moving at constant velocity into a cloud of smaller spherical grains far from any boundaries and without gravity is presented with a non-smooth contact dynamics method. A dense granular “cluster” zone builds progressively around the moving sphere until a stationary regime appears with a constant upstream cluster size. The key point is that the upstream cluster size increases with the initial solid fraction $ \phi_{0}$ but the cluster packing fraction takes an about constant value independent of $ \phi_{0}$ . Although the upstream cluster size around the moving sphere diverges when $ \phi_{0}$ approaches a critical value, the drag force exerted by the grains on the sphere does not. The detailed analysis of the local strain rate and local stress fields made in the non-parallel granular flow inside the cluster allows us to extract the local invariants of the two tensors: dilation rate, shear rate, pressure and shear stress. Despite different spatial variations of these invariants, the local friction coefficient μ appears to depend only on the local inertial number I as well as the local solid fraction, which means that a local rheology does exist in the present non-parallel flow. The key point is that the spatial variations of I inside the cluster do not depend on the sphere velocity and explore only a small range around the value one.

Les troubles du spectre de l’autisme (TSAs) sont caracterises par une alteration de la communication sociale, des interets restreints et stereotypes ou comportements stereotypes (DSM-5 [1] ). Touchant environ 1 % de la population, ils sont un defi societal majeur en termes de precocite de diagnostic et de developpement de strategies therapeutiques. Des avancees scientifiques mettent aujourd’hui en evidence dans les TSAs des alterations de cognition sociale et non sociale, avec des correlats neuro-anatomiques. Ceux-ci sont etudies par des techniques d’imagerie structurales (IRM), necessitant d’etre completes par des donnees fonctionnelle (ex. IRMf, EEG). L’EEG est la technique de neuro-imagerie la plus couramment utilisee en routine clinique du fait de sa faisabilite a tout âge et de son faible cout. Elle a montre un role important dans l’etude de l’electrophysiologie chez l’homme. Le rythme alpha 8–12 Hz (RA) est decrit particulierement durant l’etat de repos chez les individus. Elle a ete associee a l’inhibition sensorielle et cognitive [2] . Beaucoup d’etudes ont montre chez les sujets avec TSA une activite du rythme alpha anormale [3] , [4] ainsi qu’une faible suppression en reponse a l’observation d’action [5] . Cependant, les etudes n’identifient pas de pattern du RA consistant chez les sujets TSAs. Notre etude vise a tester la reproductibilite de ces resultats avec des sujets TSA diagnostiques dans le service de pedopsychiatrie et des sujets controles a l’etat de repos et ayant chacun beneficie d’un EEG clinique dans le service d’explorations fonctionnelles au sein de l’hopital Robert-Debre. Ces donnees ont permis l’analyse du RA de 49 sujets TSA apparies en âge et sexe avec des controles, soit 3 fois plus que dans la litterature scientifique, sans difference statistiquement significative. Cette absence de resultats questionne la litterature anterieure en matiere d’heterogeneite phenotypique et methodologique.

This paper focuses on improving the description of the contact between solid particles in a fluid flow. The numerical approach used is related to the fictitious domain method for the fluid–solid problem. It is associated to a gluey particle model in order to improve the behaviour of the particles during their contacts as a Lagrangian method is applied for their displacement. The numerical methodology is validated through 2D and 3D computations describing interactions of two particles in a shear flow. The results obtained show the ability of the scheme to recover the reversibility of the Stokes equations, even for 3D configurations. Finally, another example is studied with larger number of particles.

We simulate the sedimentation in a parallelepipedic container of spheres and nonconvex particles constituted by two overlapping spheres. We use the self-written code SCoPI. Thanks to an efficient handling of contacts between particles, it allowedus to consider up to 100, 000 spheres and 10,000 nonconvex particles. The packing fraction (in bulk and close to a wall) as well as the mean value and the distribution of contacts of the final packings are reported. The results obtained for the classical case of spherical particles (packing fraction: 63.7%, mean number of contacts: 6) are in agreement with previous studies and validate the algorithm. The packing fraction for nonconvex particles increases and then decreases with respect to the aspect ratio, which is similar to the ellipsoid (convex) case. The number of contacts is different from the number of neighbours, which is of course never the case for spherical particles (convex particles). The number of contacts is discontinuous when slightly increasing the aspect ratio from the spherical case: it is equal to 6 in the spherical case and to 10 in the nonconvex case. These values correspond to the isocounting values, i.e. the number of contacts is twice the number of degrees of freedom. This contrasts with the ellipsoid case, where it sharply but continuously increases. Concerning the number of neighbours, it continuously increases for small aspect ratio (which is similar to the convex particle case), but decreases for higher aspect ratio. Resume. Nous simulons la sedimentation dans un recipient parallelepipedique de spheres et de partic- ules non convexes formees de deux spheres se chevauchant. Afin de realiser ces simulations, de nouvelles fonctionnalites onte ajoutees au logiciel SCoPI initialement developpe par A. Lefebvre-Lepot. Grace ` une prise en compte efficace des contacts, il nous a permis deconsiderer jusqu'`a 100,000 spheres et 10,000 particules non convexes. La compacite (en volume et pres d'une paroi), ainsi que la valeur moyenne et la distribution du nombre de contacts des configurations finales sont decrites. Les resultats obtenus dans le cas classique de particules spheriques (compacite de 63.7%, nombre moyen de contacts de 6) sont en accord avec de precedenteset permettent de valider l'algorithme. La compacite pour les particules non convexes augmente puis diminue en fonction du rapport d'aspect, ce qui est similaire au cas (convexe) des ellipso¨odes. Le nombre de contacts est different du nombre de voisins, ce qui bien entendu n'est jamais le cas pour des spheres (particules convexes). Le nombre de contacts est discontinu lorsque l'on augmente legerement le rapport d'aspectpartir d'une sphere: il est ´ ` 6 dans le cas spherique et ` 10 dans le cas non convexe. Ces valeurs correspondent aux valeurs isostatiques, c'estdire que le nombre de contacts estal au double du nombre de degres de liberte. Ce resultat differe du cas des ellipso¨odes ou il augmente fortement mais continument. Quant au nombre de voisins, il augmente continument pour de petits rapports d'aspects (ce qui est semblable au cas des particules convexes), mais decroˆot pour de plus grands rapports d'aspects.

We investigate the behavior of fluid–particle mixtures subject to shear stress, by mean of direct simulation. This approach is meant to give some hints to explain the influence of interacting red cells on the global behavior of the blood. We concentrate on the apparent viscosity, which we define as a macroscopic quantity which characterizes the resistance of a mixture against externally imposed shear motion. Our main purpose is to explain the non-monotonous variations of this apparent viscosity when a mixture of fluid and interacting particles is submitted to shear stress during a certain time interval. Our analysis of these variations is based on preliminary theoretical remarks, and some computations for some well-chosen static configurations. To cite this article: A. Lefebvre, B. Maury, C. R. Mecanique 333 (2005).

We present here a method to simulate the motion of a rigid body in a fluid. The method is based on a variational formulation on the whole fluid/solid domain, with some constraints on the unknown and the test functions. These constraints are relaxed by introducing a penalty term, which leads to a minimization problem over unconstrained functional spaces. This makes the method straightforward to implement from any finite element Stokes/Navier-Stokes solver. It is shown that, as the penalty parameter goes to infinity, we recover the coupled fluid-solid equations. We apply this approach to a simplified 2D model of the aortic valve.

We study self propelled stokesian robots composed of assemblies of balls, in dimensions 2 and 3, and prove that they are able to control their position and orientation. This is a result of controllability, and its proof relies on applying Chow's theorem in an analytic framework, similarly to what has been done in [3] for an axisymmetric system swimming along the axis of symmetry. However, we simplify drastically the analyticity result given in [3] and apply it to a situation where more complex swimmers move either in a plane or in three-dimensional space, hence experiencing also rotations. We then focus our attention on energetically optimal strokes, which we are able to compute numerically. Some examples of computed optimal strokes are discussed in detail., Comment: 32 pages, 9 figures

Evaluation of faces is an important dimension of social relationships. A degraded sensitivity to facial perceptual cues might contribute to atypical social interactions in autism spectrum disorder (ASD). The current study investigated whether face based social judgment is atypical in ASD and if so, whether it could be related to a degraded sensitivity to facial perceptual cues. Individuals with ASD (n = 33) and IQ- and age-matched controls (n = 38) were enrolled in this study. Watching a series of photographic or synthetic faces, they had to judge them for “kindness”. In synthetic stimuli, the amount of perceptual cues available could be either large or small. We observed that social judgment was atypical in the ASD group on photographic stimuli, but, contrarily to the prediction based on the degraded sensitivity hypothesis, analyses on synthetic stimuli found a similar performance and a similar effect of the amount of perceptual cues in both groups. Further studies on perceptual differences between photographs and synthetic pictures of faces might help understand atypical social judgment in ASD.

The corpus callosum -- the main pathway for long-distance inter-hemispheric integration in the human brain -- has been frequently reported to be smaller among autistic patients compared with non-autistic controls. We conducted a meta-analysis of the literature which suggested a statistically significant difference. However, the studies included were heavily underpowered: on average only 20% power to detect differences of 0.3 standard deviations, which makes it difficult to establish the reality of such a difference. We therefore studied the size of the corpus callosum among 694 subjects (328 patients, 366 controls) from the Abide cohort. Despite having achieved 99% power to detect statistically significant differences of 0.3 standard deviations, we did not observe any. To better understand the neuroanatomical diversity of the corpus callosum, and the possible reasons for the previous findings, we analysed the relationship between its size, the size of the brain, intracranial volume and intelligence scores. The corpus callosum appeared to scale non-linearly with brain size, with large brains having a proportionally smaller corpus callosum. Additionally, intelligence scores correlated with brain volume among controls but the correlation was significantly weaker among patients. We used simulations to determine to which extent these two effects could lead to artefactual differences in corpus callosum size within populations. We observed that, were there a difference in brain volume between cases and controls, normalising corpus callosum size by brain volume would not eliminate the brain volume effect, but adding brain volume as a covariate in a linear model would. Finally, we observed that because of the weaker correlation of intelligence scores and brain volume among patients, matching populations by intelligence scores could result in a bias towards including more patients with large brain volumes, inducing an artificial difference. Overall, our results highlight the necessity for open data sharing efforts such as Abide to provide a more solid ground for the discovery of neuroimaging biomarkers, within the context of the wide human neuroanatomical diversity.

We discuss connections between low-Reynolds-number swimming and geometric control theory, and present a general algorithm for the numerical computation of energetically optimal strokes. As an illustration of our approach, we show computed motility maps and optimal strokes for two model swimmers.

We present a way to handle contacts between rigid particles in shear flow. The influence of such a modeling is shown by studying an example with 13 particles in 3D. Studying a concentrated suspension in 2D, we demonstrate that contact modelling as well as choice of boundary conditions influences the macroscopic properties of the suspension. Cet article presente une modelisation du contact entre particules solides dans un ecoulement cisaille. On montre ici l’importance du modele de contact sur un cas d’etude 3D comportant 13 particules. Une analyse plus detaillee sur une suspension concentree 2D montre l’influence des conditions aux limites et de la description du contact sur le deplacement des particules et les parametres rheologiques des suspensions.

International audience; We are interested in the existence results for second-order differential inclusions, involving finite number of unilateral constraints in an abstract framework. These constraints are described by a set-valued operator, more precisely a proximal normal cone to a timedependent set. In order to prove these existence results, we study an extension of the numerical scheme introduced in [10] and prove a convergence result for this scheme.

International audience; We consider the problem of swimming at low Reynolds numbers. This is the relevant asymptotic for micro-and nano-robots needing to navigate in an aqueous medium. As a model, we propose a robot composed of three balls. The relative positions of these balls can change according to three degrees of freedom. We prove that this robot is able to navigate in a plane by modifying the conformation of its shape. Résumé. Nous considérons le problème de la nageà faible nombre de Reynolds. C'est l'asymptotique pertinente pour les micro-et nano-robots devant se déplacer dans un milieu aqueux. Nous proposons comme modèle un robot formé de trois boules qui peuvent se déplacer les unes par rapport aux autres selon trois degrés de liberté. Nous démontrons qu'en changeant sa conformation, ce robot peut effectivement naviguer dans un plan.