Emergent Jaw Predominance in Vocal Development through Stochastic Optimization

International audienceInfant vocal babbling strongly relies on jaw oscillations , especially at the stage of canonical babbling, which underlies the syllabic structure of world languages. In this paper, we propose, model and analyze an hypothesis to explain this predominance of the jaw in early babbling. This hypothesis states that general stochastic optimization principles, when applied to learning sensorimotor control, automatically generate ordered babbling stages with a predominant exploration of jaw movements in early stages. The reason is that those movements impact the auditory effects more than other articulators. In previous computational models, such general principles were shown to selectively freeze and free degrees of freedom in a model reproducing the proximo-distal development observed in infant arm reaching. The contribution of this paper is to show how, using the same methods, we are able to explain such patterns in vocal development. We present three experiments. The two first ones show that the recruitment order of articulators emerging from stochastic optimization depends on the target sound to be achieved but that on average the jaw is largely chosen as the first recruited articulator. The third experiment analyses in more detail how the emerging recruitment order is shaped by the dynamics of the optimization process

Approches computationnelles d'analyse des relations entre cerveau et comportement

Modern neuroimaging allows us to measure the activity of our brain. Traditionally, either the sensitivity of each cerebral region, or the information that can be extracted from it are deduced, but their internal mechanisms are still poorly understood. In this thesis I propose two different methods to directly identify the neural computations governing our decisions. My first study focuses on brain mediation analysis, i.e. on the brain's role as an intermediary between a stimulus and a response. I first investigate the statistical properties of mediation tests and show a surprising property : only the central part of an information processing chain can be identified as a mediator and not the other steps, which contain either too little or too much noise. I then adapt this approach to the study of fMRI data, reduce its computational requirement and clarify its causal interpretation. Finally, I analyze a decision-making experiment and identify a link between subject loss aversion and the mediating force of the left dorsal-lateral prefrontal cortex. My second study focuses on the physiological constraints imposed on neural processes, i.e. the computations that can be performed by neurons shaped by various biological mechanisms. I first develop a test to discriminate artificial neural networks performing identical tasks but subject to different constraints. Then, I show that the Striatum and Amygdala calculations seem to be subject to a hebbian plasticity during decision making, and fianlly that the degree of plasticity predicts the degree of irrationality of each subject. Both these approaches can and should be extended to network level analysis in further work.La neuro-imagerie moderne permet de mesurer l’activité de notre cerveau. On en déduit traditionnellement soit la sensibilité de chaque région cérébrale, soit les informations qu’on peut en extraire, mais rarement leurs mécanismes internes. Dans cette thèse je propose deux méthodes différentes permettant d’identifier directement les calculs neuraux régissant nos décisions. Ma première étude se concentre sur l’analyse de médiation cérébrale, c’est-à-dire sur le rôle d’intermédiaire exercée par le cerveau entre un stimulus et une réponse. J’y étudie les caractéristiques statistiques des tests de médiation et démontre une propriété surprenante : seule la partie centrale d’une chaîne de traitement de l’information peut être identifiée comme médiatrice, les autres étapes ne contenant pas assez, ou trop, de bruit. J’adapte ensuite cette approche à l’étude des données IRMf, réduit son coût computationnel et clarifie son interprétation causale. Enfin, j’analyse une expérience de prise de décision et identifie une lien entre l’aversion à la perte des sujets et la force médiatrice du cortex préfrontal dorsolateral gauche. Ma seconde étude se concentre sur les contraintes physiologiques s’imposant aux processus neuraux, c’est-à-dire sur les calculs réalisables par des neurones façonnés par divers mécanismes biologiques. J’élabore d’abord un test permettant de discriminer des réseaux de neurones artificiels réalisant tous une même tâche, tout en étant soumis à diverses contraintes. Ensuite, je montre que les calculs du Striatum et de l’Amygdale semblent soumis à une plasticité hebbienne lors d’une prise de décision et que cette plasticité prédit le degré d’irrationalité de chaque sujet

Computational approaches for brain-behavior relationship

La neuro-imagerie moderne permet de mesurer l’activité de notre cerveau. On en déduit traditionnellement soit la sensibilité de chaque région cérébrale, soit les informations qu’on peut en extraire, mais rarement leurs mécanismes internes. Dans cette thèse je propose deux méthodes différentes permettant d’identifier directement les calculs neuraux régissant nos décisions. Ma première étude se concentre sur l’analyse de médiation cérébrale, c’est-à-dire sur le rôle d’intermédiaire exercée par le cerveau entre un stimulus et une réponse. J’y étudie les caractéristiques statistiques des tests de médiation et démontre une propriété surprenante : seule la partie centrale d’une chaîne de traitement de l’information peut être identifiée comme médiatrice, les autres étapes ne contenant pas assez, ou trop, de bruit. J’adapte ensuite cette approche à l’étude des données IRMf, réduit son coût computationnel et clarifie son interprétation causale. Enfin, j’analyse une expérience de prise de décision et identifie une lien entre l’aversion à la perte des sujets et la force médiatrice du cortex préfrontal dorsolateral gauche. Ma seconde étude se concentre sur les contraintes physiologiques s’imposant aux processus neuraux, c’est-à-dire sur les calculs réalisables par des neurones façonnés par divers mécanismes biologiques. J’élabore d’abord un test permettant de discriminer des réseaux de neurones artificiels réalisant tous une même tâche, tout en étant soumis à diverses contraintes. Ensuite, je montre que les calculs du Striatum et de l’Amygdale semblent soumis à une plasticité hebbienne lors d’une prise de décision et que cette plasticité prédit le degré d’irrationalité de chaque sujet.Modern neuroimaging allows us to measure the activity of our brain. Traditionally, either the sensitivity of each cerebral region, or the information that can be extracted from it are deduced, but their internal mechanisms are still poorly understood. In this thesis I propose two different methods to directly identify the neural computations governing our decisions. My first study focuses on brain mediation analysis, i.e. on the brain's role as an intermediary between a stimulus and a response. I first investigate the statistical properties of mediation tests and show a surprising property : only the central part of an information processing chain can be identified as a mediator and not the other steps, which contain either too little or too much noise. I then adapt this approach to the study of fMRI data, reduce its computational requirement and clarify its causal interpretation. Finally, I analyze a decision-making experiment and identify a link between subject loss aversion and the mediating force of the left dorsal-lateral prefrontal cortex. My second study focuses on the physiological constraints imposed on neural processes, i.e. the computations that can be performed by neurons shaped by various biological mechanisms. I first develop a test to discriminate artificial neural networks performing identical tasks but subject to different constraints. Then, I show that the Striatum and Amygdala calculations seem to be subject to a hebbian plasticity during decision making, and fianlly that the degree of plasticity predicts the degree of irrationality of each subject. Both these approaches can and should be extended to network level analysis in further work

Emergent maturation from stochastic optimization in vocal development

The aim of this paper is to propose and computationally support an original hypothesis regarding the predominance of jaw movements in infant speech development. We capitalize on previous research on emergent maturations from a stochastic optimization process on the arm domain. This work has shown that a quite simple optimization process, allowing a progressive learning of reaching arm movements by the minimization of a cost function, can display an emergent sensorimotor maturation: without precoding it, such an algorithm naturally recruits in priority proximal joints due to their wider range of effects. Here, we adapt this work to the vocal domain, by the use of a vocal tract model, and show that a similar effect can occurs on particular conditions, recruiting the jaw in priority due to the wider range of auditory effects implied by moving this articulator

La négociation d’« entreprise » en pratiques: Plural configurations and actor strategies

International audiencePromoting company collective bargaining has been at the core of the French industrial relations system reforms. The stated objective is that of establishing local regulation, making it possible to build effective compromises between the diverse interests within the company. What about in practice? Using the REPONSE survey (2017) and administrative data on the geographical location of establishments from the FLORES database (2017), the article shows that the collective bargaining space is structured in four configurations and that the most frequent bargaining configuration does not correspond to local regulation. Using company case studies, we then show how, behind these configurations, the balance of power between the legal negotiation actors are played out and how their respective strategies contribute to defining the negotiation space most conducive to serve their respective intentions.La promotion de la négociation collective d’entreprise est au cœur des réformes successives du système français de relations professionnelles. L’objectif affiché est celui de l’instauration d’une régulation de proximité, permettant de construire des compromis efficaces entre la diversité des intérêts existant au sein de l’entreprise. Qu’en est-il en pratique ? Prenant appui sur une exploitation de l’enquête REPONSE (2017) appareillée à des données administratives sur l’implantation géographique des établissements issues de la base FLORES (2017), l’article montre que l’espace de la négociation collective se structure en quatre configurations et que la configuration de négociation la plus fréquente ne correspond pas à une régulation de proximité. Mobilisant des études de cas d’entreprise, nous montrons ensuite comment, derrière ces configurations, se jouent des rapports de forces entre les acteurs légaux de la négociation et comment leurs stratégies respectives contribuent à définir l’espace de négociation le plus propice à servir leurs intentions réciproques

La négociation d’« entreprise » en pratiques: Plural configurations and actor strategies

International audiencePromoting company collective bargaining has been at the core of the French industrial relations system reforms. The stated objective is that of establishing local regulation, making it possible to build effective compromises between the diverse interests within the company. What about in practice? Using the REPONSE survey (2017) and administrative data on the geographical location of establishments from the FLORES database (2017), the article shows that the collective bargaining space is structured in four configurations and that the most frequent bargaining configuration does not correspond to local regulation. Using company case studies, we then show how, behind these configurations, the balance of power between the legal negotiation actors are played out and how their respective strategies contribute to defining the negotiation space most conducive to serve their respective intentions.La promotion de la négociation collective d’entreprise est au cœur des réformes successives du système français de relations professionnelles. L’objectif affiché est celui de l’instauration d’une régulation de proximité, permettant de construire des compromis efficaces entre la diversité des intérêts existant au sein de l’entreprise. Qu’en est-il en pratique ? Prenant appui sur une exploitation de l’enquête REPONSE (2017) appareillée à des données administratives sur l’implantation géographique des établissements issues de la base FLORES (2017), l’article montre que l’espace de la négociation collective se structure en quatre configurations et que la configuration de négociation la plus fréquente ne correspond pas à une régulation de proximité. Mobilisant des études de cas d’entreprise, nous montrons ensuite comment, derrière ces configurations, se jouent des rapports de forces entre les acteurs légaux de la négociation et comment leurs stratégies respectives contribuent à définir l’espace de négociation le plus propice à servir leurs intentions réciproques

Neural shape mediation analysis

Abstract Neural signal shapes convey significant information about their generating processes. In this study, we introduce a data-driven methodology to identify sensory and behaviourally-relevant traces within neural responses. We present a phenomenological model that characterises temporal variations in intracranial EEG using eight interpretable parameters: peak time, peak intensity, initial and final baselines, accumulation and depletion period, and their respective concavities. This model effectively captures subtle signal variations, especially in sensory decision-making tasks. By decomposing the signals in this manner, we then conduct a comprehensive brain mediation analysis on iEEG data’s shape, pinpointing regions that mediate behavioural processes. Importantly, we can determine which signal dynamics specifically reflect underlying behavioural processes, enhancing the depth of analysis and critique of their role in behaviour. Preliminary applications on a cohort of epileptic patients reveal that our model explains over a third of the signal variance at the trial level across all brain regions. We identified four key regions—encompassing sensory, associative, frontal, and premotor areas—that mediate the impact of task difficulty on reaction time. Notably, in these regions, it was the depletion period, rather than signal amplitude, that correlated with behavioural speed. This study highlights the potential of our approach in providing detailed insights into the neural mechanisms linking stimuli to behaviour

EZH2 inhibition reduces cartilage loss and functional impairment related to osteoarthritis

International audienceHistone methyltransferase EZH2 is upregulated during osteoarthritis (OA), which is the most widespread rheumatic disease worldwide, and a leading cause of disability. This study aimed to assess the impact of EZH2 inhibition on cartilage degradation, inflammation and functional disability. In vitro, gain and loss of EZH2 function were performed in human articular OA chondrocytes stimulated with IL-1β. In vivo, the effects of EZH2 inhibition were investigated on medial meniscectomy (MMX) OA mouse model. The tissue alterations were assayed by histology and the functional disabilities of the mice by actimetry and running wheel. In vitro, EZH2 overexpression exacerbated the action of IL-1β in chondrocytes increasing the expression of genes involved in inflammation, pain (NO, PGE2, IL6, NGF) and catabolism (MMPs), whereas EZH2 inhibition by a pharmacological inhibitor, EPZ-6438, reduced IL-1β effects. Ex vivo, EZH2 inhibition decreased IL-1β-induced degradation of cartilage. In vivo, intra-articular injections of the EZH2 inhibitor reduced cartilage degradation and improved motor functions of OA mice. This study demonstrates that the pharmacological inhibition of the histone methyl-transferase EZH2 slows the progression of osteoarthritis and improves motor functions in an experimental OA model, suggesting that EZH2 could be an effective target for the treatment of OA by reducing catabolism, inflammation and pain. Abbreviations DNZep 3-Deazanoplanocin A EZH2 Enhancer of Zest Homolog 2 GFP Green Fluorescent Protein H3K27 Lysine 27 of the histone 3 IL-1β Interleukin-1β IL-6 Interleukin 6 JMJD3 Jumonji Domain Containing 3 MMP Matrix metalloproteinase MMX Medial meniscectomy NGF Nerve Growth Factor NO Nitric oxide OA Osteoarthritis PGE2 Prostaglandin E2 Osteoarthritis (OA) is the most widespread rheumatic disease worldwide, and one of the main causes of pain and disability, reducing patient's quality of life 1. OA affects 1 in 3 people over age 65 and women more than men 2. In the United States, 22.7% of the adult population (52.5 million of persons) report having been diagnosed with OA by their physician. The impact on healthcare expenses is massive. The cost of knee OA alone is, for instance