47 research outputs found
Federated Learning Aggregation: New Robust Algorithms with Guarantees
Federated Learning has been recently proposed for distributed model training
at the edge. The principle of this approach is to aggregate models learned on
distributed clients to obtain a new more general "average" model (FedAvg). The
resulting model is then redistributed to clients for further training. To date,
the most popular federated learning algorithm uses coordinate-wise averaging of
the model parameters for aggregation. In this paper, we carry out a complete
general mathematical convergence analysis to evaluate aggregation strategies in
a federated learning framework. From this, we derive novel aggregation
algorithms which are able to modify their model architecture by differentiating
client contributions according to the value of their losses. Moreover, we go
beyond the assumptions introduced in theory, by evaluating the performance of
these strategies and by comparing them with the one of FedAvg in classification
tasks in both the IID and the Non-IID framework without additional hypothesis
Clinical review: Prognostic value of magnetic resonance imaging in acute brain injury and coma
Progress in management of critically ill neurological patients has led to improved survival rates. However, severe residual neurological impairment, such as persistent coma, occurs in some survivors. This raises concerns about whether it is ethically appropriate to apply aggressive care routinely, which is also associated with burdensome long-term management costs. Adapting the management approach based on long-term neurological prognosis represents a major challenge to intensive care. Magnetic resonance imaging (MRI) can show brain lesions that are not visible by computed tomography, including early cytotoxic oedema after ischaemic stroke, diffuse axonal injury after traumatic brain injury and cortical laminar necrosis after cardiac arrest. Thus, MRI increases the accuracy of neurological diagnosis in critically ill patients. In addition, there is some evidence that MRI may have potential in terms of predicting outcome. Following a brief description of the sequences used, this review focuses on the prognostic value of MRI in patients with traumatic brain injury, anoxic/hypoxic encephalopathy and stroke. Finally, the roles played by the main anatomical structures involved in arousal and awareness are discussed and avenues for future research suggested
Two Distinct Dynamic Modes Subtend the Detection of Unexpected Sounds
International audienceThe brain response to auditory novelty comprises two main EEG components: an early mismatch negativity and a late P300. Whereas the former has been proposed to reflect a prediction error, the latter is often associated with working memory updating. Interestingly, these two proposals predict fundamentally different dynamics: prediction errors are thought to propagate serially through several distinct brain areas, while working memory supposes that activity is sustained over time within a stable set of brain areas. Here we test this temporal dissociation by showing how the generalization of brain activity patterns across time can characterize the dynamics of the underlying neural processes. This method is applied to magnetoencephalography (MEG) recordings acquired from healthy participants who were presented with two types of auditory novelty. Following our predictions, the results show that the mismatch evoked by a local novelty leads to the sequential recruitment of distinct and short-lived patterns of brain activity. In sharp contrast, the global novelty evoked by an unexpected sequence of five sounds elicits a sustained state of brain activity that lasts for several hundreds of milliseconds. The present results highlight how MEG combined with multivariate pattern analyses can characterize the dynamics of human cortical processes
Involvement of mast cells and intracellular signaling pathways in the development of the human adrenal glands
La mise en place de la voie de synthĂšse des minĂ©ralocorticoĂŻdes au cours du dĂ©veloppement foetal chez lâhomme reste un processus encore non totalement Ă©lucidĂ©, que ce soit du point de vue de la chronologie dâexpression des enzymes de la stĂ©roĂŻdogenĂšse ou bien des acteurs dĂ©terminant la production dâaldostĂ©rone en pĂ©riode pĂ©ri-natale. Chez lâadulte, la sĂ©crĂ©tion dâaldostĂ©rone est contrĂŽlĂ©e majoritairement par des facteurs circulants tels que le systĂšme rĂ©nine angiotensine et le potassium. Lâimportance des mĂ©canismes paracrines a Ă©tĂ© plus rĂ©cemment dĂ©montrĂ©, impliquant diffĂ©rents acteurs, dont les mastocytes intra-surrĂ©naliens situĂ©s dans la rĂ©gion sous-capsulaire. En effet, les produits de sĂ©crĂ©tion mastocytaire stimulent la production dâaldostĂ©rone par lâintermĂ©diaire de la libĂ©ration de sĂ©rotonine et de lâactivation des rĂ©cepteurs sĂ©rotoninergiques de type 4 prĂ©sents Ă la surface des cellules stĂ©roĂŻdogĂšnes. Cependant, le rĂŽle des mastocytes et de la voie sĂ©rotoninergique dans le dĂ©veloppement surrĂ©nalien nâa jamais Ă©tĂ© Ă©tudiĂ©. Dans ce travail, nous montrons que les mastocytes colonisent la surrĂ©nale foetale vers 18 semaines dâamĂ©norrhĂ©e (SA) dans la zone dĂ©finitive de façon conjointe Ă lâapparition des premiĂšres cellules exprimant la 3ÎČ-hydroxystĂ©roĂŻde dĂ©shydrogĂ©nase. LâaldostĂ©rone synthase (CYP11B2) est dĂ©tectĂ©e dans la mĂȘme zone vers 24 SA, puis son expression augmente au cours du dĂ©veloppement. De façon intĂ©ressante, nous mettons en Ă©vidence une densitĂ© mastocytaire ainsi quâune expression de CYP11B2 plus importantes chez les foetus comparĂ©s aux nouveau-nĂ©s de termes Ă©quivalents, suggĂ©rant lâimplication des mastocytes dans le processus dâadaptation Ă la vie extra-utĂ©rine. Par ailleurs, nous rapportons une activation des voies de signalisation Wnt/ÎČ-catĂ©nine et Shh au cours du dĂ©veloppement surrĂ©nalien, qui ne semble pas contrĂŽler la prolifĂ©ration cellulaire. La voie Shh pourrait ĂȘtre associĂ©e Ă lâacquisition du phĂ©notype stĂ©roĂŻdogĂšne mature alors que la voie ÎČ-catĂ©nine qui est active antĂ©rieurement Ă lâexpression de CYP11B2 ne semble pas suffisante pour initier la fonction minĂ©ralocorticoĂŻde. Globalement, ce travail montre la chronologie de la diffĂ©renciation de la zone dĂ©finitive surrĂ©nalienne au cours du dĂ©veloppement et rĂ©vĂšle pour la premiĂšre fois la mise en place de systĂšme de rĂ©gulation paracrine impliquĂ©e dans la production dâaldostĂ©rone en antĂ© et post-natal.The establishment of the mineralocorticoid synthesis pathway during fetal development in humans remains a process that has not been fully elucidated, whether from the point of view of the chronology of expression of the enzymes of steroidogenesis or of the actors involved in the production of aldosterone in the peri-natal period. In adults, aldosterone secretion is mainly controlled by circulating factors such as the renin angiotensin system and potassium. The importance of paracrine mechanisms has more recently been demonstrated, involving different actors, like intra-adrenal mast cells located in the subcapsular region. Mast cell secretion stimulate the production of aldosterone through the release of serotonin and the activation of type 4 serotonergic receptors present on the surface of steroidogenic cells. However, the role of mast cells and the serotonin pathway in adrenal development has never been studied. In this work, we show that mast cells colonize the fetal adrenal gland around 18 weeks of gestation (WG) in the definitive area in conjunction with the appearance of the first cells expressing 3ÎČ-hydroxysteroid dehydrogenase. Aldosterone synthase (CYP11B2) is detected in the same area around 24 weeks, and then its expression increases during development. Interestingly, we highlight a mast cell density as well as an expression of CYP11B2 higher in fetuses compared to newborns of equivalent terms, suggesting the involvement of mast cells in the process of adaptation to extra-uterine life. Furthermore, we report an activation of the Wnt/ÎČ-catenin and Shh signaling pathways during adrenal development, which does not appear to control cell proliferation. The Shh pathway could be associated with the acquisition of the mature steroidogenic phenotype whereas the ÎČ-catenin pathway, which is active prior to the expression of CYP11B2, does not appear to be sufficient to initiate mineralocorticoid function. Overall, this work shows the chronology of the differentiation of the definitive adrenal zone during development and reveals for the first time the establishment of the paracrine regulatory system involved in the production of aldosterone in the ante and postnatal period
Le retard pubertaire chez le garçonâ : effets Ă long terme du traitement par androgĂšnes
Le retard pubertaire du garçon est dit dans 2/3 des cas, "simple" câest-Ă -dire correspondant Ă un simple dĂ©calage temporel. Il est parfois traitĂ© par injections mensuelles d'androgĂšnes. Toutefois, les effets Ă moyen et long terme restent peu connus, d'autant plus qu'il a Ă©tĂ© montrĂ© rĂ©cemment que lâadministration de hautes doses de testostĂ©rone pouvait entrainer une suppression de la spermatogĂ©nĂšse chez des hommes sains. Le but principal de lâĂ©tude a donc Ă©tĂ© dâĂ©valuer de façon rĂ©trospective lâimpact sur la fertilitĂ© du traitement par androgĂšnes, les objectifs secondaires Ă©tant l'Ă©tude de la taille finale, la sociabilitĂ© et le retentissement psychologique. MĂ©thodes : Il s'agit d'une Ă©tude rĂ©trospective bicentrique rouennaise incluant tous les garçons qui ont Ă©tĂ© suivis entre 1982 et 2005 soit au CHU soit en cabinet de ville pour retard pubertaire. AprĂšs analyse des causes du retard pubertaire, des questionnaires ont Ă©tĂ© envoyĂ© aux patients adultes qui avaient Ă©tĂ© traitĂ©s pour un retard pubertaire simple ainsi qu'Ă des patients non traitĂ©s dit "contrĂŽles", aprĂšs appariement sur lâĂąge Ă la 1re consultation et sur lâĂąge actuel. RĂ©sultats : 45 patients ont Ă©tĂ© inclus dans l'Ă©tude parmi lesquels 5 patients traitĂ©s par androgĂšnes pour un retard pubertaire simple. Les donnĂ©es Ă long terme ont Ă©tĂ© recueillies pour 5 patients (30%) : 2 traitĂ©s, et 3 contrĂŽles. Aucun trouble de fertilitĂ© nâa Ă©tĂ© signalĂ© chez les patients traitĂ©s et dans tous les cas, la taille finale correspondait Ă la taille cible gĂ©nĂ©tique. Lâimpact psychologique est apparu plus important chez les sujets non traitĂ©s, avec un retentissement sur la vie sociale, scolaire et professionnelle. Conclusion : Cette Ă©tude pointe la difficultĂ© du diagnostic Ă©tiologique du retard pubertaire et montre sur 5 patients que le traitement ne semble pas impacter la fertilitĂ© mais amĂ©liorer le vĂ©cu psychologique Ă l'adolescence. Cependant, des Ă©tudes complĂ©mentaires sur une plus large population sont nĂ©cessaires afin de confirmer ces rĂ©sultats
Implication des mastocytes et des voies de signalisation intra-cellulaire dans le développement des glandes surrénales humaines
The establishment of the mineralocorticoid synthesis pathway during fetal development in humans remains a process that has not been fully elucidated, whether from the point of view of the chronology of expression of the enzymes of steroidogenesis or of the actors involved in the production of aldosterone in the peri-natal period. In adults, aldosterone secretion is mainly controlled by circulating factors such as the renin angiotensin system and potassium. The importance of paracrine mechanisms has more recently been demonstrated, involving different actors, like intra-adrenal mast cells located in the subcapsular region. Mast cell secretion stimulate the production of aldosterone through the release of serotonin and the activation of type 4 serotonergic receptors present on the surface of steroidogenic cells. However, the role of mast cells and the serotonin pathway in adrenal development has never been studied. In this work, we show that mast cells colonize the fetal adrenal gland around 18 weeks of gestation (WG) in the definitive area in conjunction with the appearance of the first cells expressing 3ÎČ-hydroxysteroid dehydrogenase. Aldosterone synthase (CYP11B2) is detected in the same area around 24 weeks, and then its expression increases during development. Interestingly, we highlight a mast cell density as well as an expression of CYP11B2 higher in fetuses compared to newborns of equivalent terms, suggesting the involvement of mast cells in the process of adaptation to extra-uterine life. Furthermore, we report an activation of the Wnt/ÎČ-catenin and Shh signaling pathways during adrenal development, which does not appear to control cell proliferation. The Shh pathway could be associated with the acquisition of the mature steroidogenic phenotype whereas the ÎČ-catenin pathway, which is active prior to the expression of CYP11B2, does not appear to be sufficient to initiate mineralocorticoid function. Overall, this work shows the chronology of the differentiation of the definitive adrenal zone during development and reveals for the first time the establishment of the paracrine regulatory system involved in the production of aldosterone in the ante and postnatal period.La mise en place de la voie de synthĂšse des minĂ©ralocorticoĂŻdes au cours du dĂ©veloppement foetal chez lâhomme reste un processus encore non totalement Ă©lucidĂ©, que ce soit du point de vue de la chronologie dâexpression des enzymes de la stĂ©roĂŻdogenĂšse ou bien des acteurs dĂ©terminant la production dâaldostĂ©rone en pĂ©riode pĂ©ri-natale. Chez lâadulte, la sĂ©crĂ©tion dâaldostĂ©rone est contrĂŽlĂ©e majoritairement par des facteurs circulants tels que le systĂšme rĂ©nine angiotensine et le potassium. Lâimportance des mĂ©canismes paracrines a Ă©tĂ© plus rĂ©cemment dĂ©montrĂ©, impliquant diffĂ©rents acteurs, dont les mastocytes intra-surrĂ©naliens situĂ©s dans la rĂ©gion sous-capsulaire. En effet, les produits de sĂ©crĂ©tion mastocytaire stimulent la production dâaldostĂ©rone par lâintermĂ©diaire de la libĂ©ration de sĂ©rotonine et de lâactivation des rĂ©cepteurs sĂ©rotoninergiques de type 4 prĂ©sents Ă la surface des cellules stĂ©roĂŻdogĂšnes. Cependant, le rĂŽle des mastocytes et de la voie sĂ©rotoninergique dans le dĂ©veloppement surrĂ©nalien nâa jamais Ă©tĂ© Ă©tudiĂ©. Dans ce travail, nous montrons que les mastocytes colonisent la surrĂ©nale foetale vers 18 semaines dâamĂ©norrhĂ©e (SA) dans la zone dĂ©finitive de façon conjointe Ă lâapparition des premiĂšres cellules exprimant la 3ÎČ-hydroxystĂ©roĂŻde dĂ©shydrogĂ©nase. LâaldostĂ©rone synthase (CYP11B2) est dĂ©tectĂ©e dans la mĂȘme zone vers 24 SA, puis son expression augmente au cours du dĂ©veloppement. De façon intĂ©ressante, nous mettons en Ă©vidence une densitĂ© mastocytaire ainsi quâune expression de CYP11B2 plus importantes chez les foetus comparĂ©s aux nouveau-nĂ©s de termes Ă©quivalents, suggĂ©rant lâimplication des mastocytes dans le processus dâadaptation Ă la vie extra-utĂ©rine. Par ailleurs, nous rapportons une activation des voies de signalisation Wnt/ÎČ-catĂ©nine et Shh au cours du dĂ©veloppement surrĂ©nalien, qui ne semble pas contrĂŽler la prolifĂ©ration cellulaire. La voie Shh pourrait ĂȘtre associĂ©e Ă lâacquisition du phĂ©notype stĂ©roĂŻdogĂšne mature alors que la voie ÎČ-catĂ©nine qui est active antĂ©rieurement Ă lâexpression de CYP11B2 ne semble pas suffisante pour initier la fonction minĂ©ralocorticoĂŻde. Globalement, ce travail montre la chronologie de la diffĂ©renciation de la zone dĂ©finitive surrĂ©nalienne au cours du dĂ©veloppement et rĂ©vĂšle pour la premiĂšre fois la mise en place de systĂšme de rĂ©gulation paracrine impliquĂ©e dans la production dâaldostĂ©rone en antĂ© et post-natal
Implication des mastocytes et des voies de signalisation intra-cellulaire dans le développement des glandes surrénales humaines
The establishment of the mineralocorticoid synthesis pathway during fetal development in humans remains a process that has not been fully elucidated, whether from the point of view of the chronology of expression of the enzymes of steroidogenesis or of the actors involved in the production of aldosterone in the peri-natal period. In adults, aldosterone secretion is mainly controlled by circulating factors such as the renin angiotensin system and potassium. The importance of paracrine mechanisms has more recently been demonstrated, involving different actors, like intra-adrenal mast cells located in the subcapsular region. Mast cell secretion stimulate the production of aldosterone through the release of serotonin and the activation of type 4 serotonergic receptors present on the surface of steroidogenic cells. However, the role of mast cells and the serotonin pathway in adrenal development has never been studied. In this work, we show that mast cells colonize the fetal adrenal gland around 18 weeks of gestation (WG) in the definitive area in conjunction with the appearance of the first cells expressing 3ÎČ-hydroxysteroid dehydrogenase. Aldosterone synthase (CYP11B2) is detected in the same area around 24 weeks, and then its expression increases during development. Interestingly, we highlight a mast cell density as well as an expression of CYP11B2 higher in fetuses compared to newborns of equivalent terms, suggesting the involvement of mast cells in the process of adaptation to extra-uterine life. Furthermore, we report an activation of the Wnt/ÎČ-catenin and Shh signaling pathways during adrenal development, which does not appear to control cell proliferation. The Shh pathway could be associated with the acquisition of the mature steroidogenic phenotype whereas the ÎČ-catenin pathway, which is active prior to the expression of CYP11B2, does not appear to be sufficient to initiate mineralocorticoid function. Overall, this work shows the chronology of the differentiation of the definitive adrenal zone during development and reveals for the first time the establishment of the paracrine regulatory system involved in the production of aldosterone in the ante and postnatal period.La mise en place de la voie de synthĂšse des minĂ©ralocorticoĂŻdes au cours du dĂ©veloppement foetal chez lâhomme reste un processus encore non totalement Ă©lucidĂ©, que ce soit du point de vue de la chronologie dâexpression des enzymes de la stĂ©roĂŻdogenĂšse ou bien des acteurs dĂ©terminant la production dâaldostĂ©rone en pĂ©riode pĂ©ri-natale. Chez lâadulte, la sĂ©crĂ©tion dâaldostĂ©rone est contrĂŽlĂ©e majoritairement par des facteurs circulants tels que le systĂšme rĂ©nine angiotensine et le potassium. Lâimportance des mĂ©canismes paracrines a Ă©tĂ© plus rĂ©cemment dĂ©montrĂ©, impliquant diffĂ©rents acteurs, dont les mastocytes intra-surrĂ©naliens situĂ©s dans la rĂ©gion sous-capsulaire. En effet, les produits de sĂ©crĂ©tion mastocytaire stimulent la production dâaldostĂ©rone par lâintermĂ©diaire de la libĂ©ration de sĂ©rotonine et de lâactivation des rĂ©cepteurs sĂ©rotoninergiques de type 4 prĂ©sents Ă la surface des cellules stĂ©roĂŻdogĂšnes. Cependant, le rĂŽle des mastocytes et de la voie sĂ©rotoninergique dans le dĂ©veloppement surrĂ©nalien nâa jamais Ă©tĂ© Ă©tudiĂ©. Dans ce travail, nous montrons que les mastocytes colonisent la surrĂ©nale foetale vers 18 semaines dâamĂ©norrhĂ©e (SA) dans la zone dĂ©finitive de façon conjointe Ă lâapparition des premiĂšres cellules exprimant la 3ÎČ-hydroxystĂ©roĂŻde dĂ©shydrogĂ©nase. LâaldostĂ©rone synthase (CYP11B2) est dĂ©tectĂ©e dans la mĂȘme zone vers 24 SA, puis son expression augmente au cours du dĂ©veloppement. De façon intĂ©ressante, nous mettons en Ă©vidence une densitĂ© mastocytaire ainsi quâune expression de CYP11B2 plus importantes chez les foetus comparĂ©s aux nouveau-nĂ©s de termes Ă©quivalents, suggĂ©rant lâimplication des mastocytes dans le processus dâadaptation Ă la vie extra-utĂ©rine. Par ailleurs, nous rapportons une activation des voies de signalisation Wnt/ÎČ-catĂ©nine et Shh au cours du dĂ©veloppement surrĂ©nalien, qui ne semble pas contrĂŽler la prolifĂ©ration cellulaire. La voie Shh pourrait ĂȘtre associĂ©e Ă lâacquisition du phĂ©notype stĂ©roĂŻdogĂšne mature alors que la voie ÎČ-catĂ©nine qui est active antĂ©rieurement Ă lâexpression de CYP11B2 ne semble pas suffisante pour initier la fonction minĂ©ralocorticoĂŻde. Globalement, ce travail montre la chronologie de la diffĂ©renciation de la zone dĂ©finitive surrĂ©nalienne au cours du dĂ©veloppement et rĂ©vĂšle pour la premiĂšre fois la mise en place de systĂšme de rĂ©gulation paracrine impliquĂ©e dans la production dâaldostĂ©rone en antĂ© et post-natal
FedControl: When Control Theory Meets Federated Learning
To date, the most popular federated learning algorithms use coordinate-wise
averaging of the model parameters. We depart from this approach by
differentiating client contributions according to the performance of local
learning and its evolution. The technique is inspired from control theory and
its classification performance is evaluated extensively in IID framework and
compared with FedAvg.Comment: arXiv admin note: substantial text overlap with arXiv:2205.1086
Federated Learning Aggregation: New Robust Algorithms with Guarantees
International audienceFederated Learning has been recently proposed for distributed model training at the edge. The principle of this approach is to aggregate models learned on distributed clients to obtain a new more general "average" model (FedAvg). The resulting model is then redistributed to clients for further training. To date, the most popular federated learning algorithm uses coordinate-wise averaging of the model parameters for aggregation. In this paper, we carry out a complete general mathematical convergence analysis to evaluate aggregation strategies in a federated learning framework. From this, we derive novel aggregation algorithms which are able to modify their model architecture by differentiating client contributions according to the value of their losses. Moreover, we go beyond the assumptions introduced in theory, by evaluating the performance of these strategies and by comparing them with the one of FedAvg in classification tasks in both the IID and the Non-IID framework without additional hypothesis
FedControl: When Control Theory Meets Federated Learning
International audienceTo date, the most popular federated learning algorithms use coordinate-wise averaging of the model parameters. We depart from this approach by differentiating client contributions according to the performance of local learning and its evolution. The technique is inspired from control theory and its classification performance is evaluated extensively in IID framework and compared with FedAvg