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1. Neuromorphic Programming: Emerging Directions for Brain-Inspired Hardware

Author

Abreu, Steven and Pedersen, Jens E.

Subjects
Computer Science - Neural and Evolutionary Computing, Computer Science - Artificial Intelligence, Computer Science - Distributed, Parallel, and Cluster Computing, Computer Science - Emerging Technologies, Computer Science - Programming Languages
Abstract

The value of brain-inspired neuromorphic computers critically depends on our ability to program them for relevant tasks. Currently, neuromorphic hardware often relies on machine learning methods adapted from deep learning. However, neuromorphic computers have potential far beyond deep learning if we can only harness their energy efficiency and full computational power. Neuromorphic programming will necessarily be different from conventional programming, requiring a paradigm shift in how we think about programming. This paper presents a conceptual analysis of programming within the context of neuromorphic computing, challenging conventional paradigms and proposing a framework that aligns more closely with the physical intricacies of these systems. Our analysis revolves around five characteristics that are fundamental to neuromorphic programming and provides a basis for comparison to contemporary programming methods and languages. By studying past approaches, we contribute a framework that advocates for underutilized techniques and calls for richer abstractions to effectively instrument the new hardware class., Comment: Accepted to International Conference on Neuromorphic Systems (ICONS) 2024. arXiv admin note: substantial text overlap with arXiv:2310.18260

Published
2024

2. Steering Large Language Models using Conceptors: Improving Addition-Based Activation Engineering

Author

Postmus, Joris and Abreu, Steven

Subjects
Computer Science - Neural and Evolutionary Computing, Computer Science - Machine Learning
Abstract

Large language models have transformed AI, yet reliably controlling their outputs remains a challenge. This paper explores activation engineering, where outputs of pre-trained LLMs are controlled by manipulating their activations at inference time. Unlike traditional methods using a single steering vector, we introduce conceptors - mathematical constructs that represent sets of activation vectors as ellipsoidal regions. Conceptors act as soft projection matrices and offer more precise control over complex activation patterns. Our experiments demonstrate that conceptors outperform traditional methods across multiple steering tasks. We further use Boolean operations on conceptors for combined steering goals that empirically outperform additively combining steering vectors on a set of tasks. These results highlight conceptors as a promising tool for more effective steering of LLMs. Our code is available on github.com/jorispos/conceptorsteering., Comment: Presented at the MINT workshop at NeurIPS 2024

Published
2024

3. EmBARDiment: an Embodied AI Agent for Productivity in XR

Author

Bovo, Riccardo, Abreu, Steven, Ahuja, Karan, Gonzalez, Eric J, Cheng, Li-Te, and Gonzalez-Franco, Mar

Subjects
Computer Science - Human-Computer Interaction, Computer Science - Multiagent Systems
Abstract

XR devices running chat-bots powered by Large Language Models (LLMs) have tremendous potential as always-on agents that can enable much better productivity scenarios. However, screen based chat-bots do not take advantage of the the full-suite of natural inputs available in XR, including inward facing sensor data, instead they over-rely on explicit voice or text prompts, sometimes paired with multi-modal data dropped as part of the query. We propose a solution that leverages an attention framework that derives context implicitly from user actions, eye-gaze, and contextual memory within the XR environment. This minimizes the need for engineered explicit prompts, fostering grounded and intuitive interactions that glean user insights for the chat-bot. Our user studies demonstrate the imminent feasibility and transformative potential of our approach to streamline user interaction in XR with chat-bots, while offering insights for the design of future XR-embodied LLM agents.

Published
2024

4. Mamba-PTQ: Outlier Channels in Recurrent Large Language Models

Author

Pierro, Alessandro and Abreu, Steven

Subjects
Computer Science - Machine Learning, Computer Science - Artificial Intelligence, Computer Science - Neural and Evolutionary Computing
Abstract

Modern recurrent layers are emerging as a promising path toward edge deployment of foundation models, especially in the context of large language models (LLMs). Compressing the whole input sequence in a finite-dimensional representation enables recurrent layers to model long-range dependencies while maintaining a constant inference cost for each token and a fixed memory requirement. However, the practical deployment of LLMs in resource-limited environments often requires further model compression, such as quantization and pruning. While these techniques are well-established for attention-based models, their effects on recurrent layers remain underexplored. In this preliminary work, we focus on post-training quantization for recurrent LLMs and show that Mamba models exhibit the same pattern of outlier channels observed in attention-based LLMs. We show that the reason for the difficulty of quantizing SSMs is caused by activation outliers, similar to those observed in transformer-based LLMs. We report baseline results for post-training quantization of Mamba that do not take into account the activation outliers and suggest first steps for outlier-aware quantization., Comment: Work presented at the Efficient Systems for Foundation Models Workshop @ ICML2024

Published
2024

5. PARSE-Ego4D: Personal Action Recommendation Suggestions for Egocentric Videos

Author

Abreu, Steven, Do, Tiffany D., Ahuja, Karan, Gonzalez, Eric J., Payne, Lee, McDuff, Daniel, and Gonzalez-Franco, Mar

Subjects
Computer Science - Computer Vision and Pattern Recognition, Computer Science - Human-Computer Interaction, Computer Science - Neural and Evolutionary Computing
Abstract

Intelligent assistance involves not only understanding but also action. Existing ego-centric video datasets contain rich annotations of the videos, but not of actions that an intelligent assistant could perform in the moment. To address this gap, we release PARSE-Ego4D, a new set of personal action recommendation annotations for the Ego4D dataset. We take a multi-stage approach to generating and evaluating these annotations. First, we used a prompt-engineered large language model (LLM) to generate context-aware action suggestions and identified over 18,000 action suggestions. While these synthetic action suggestions are valuable, the inherent limitations of LLMs necessitate human evaluation. To ensure high-quality and user-centered recommendations, we conducted a large-scale human annotation study that provides grounding in human preferences for all of PARSE-Ego4D. We analyze the inter-rater agreement and evaluate subjective preferences of participants. Based on our synthetic dataset and complete human annotations, we propose several new tasks for action suggestions based on ego-centric videos. We encourage novel solutions that improve latency and energy requirements. The annotations in PARSE-Ego4D will support researchers and developers who are working on building action recommendation systems for augmented and virtual reality systems.

Published
2024

6. Q-S5: Towards Quantized State Space Models

Author

Abreu, Steven, Pedersen, Jens E., Heckel, Kade M., and Pierro, Alessandro

Subjects
Computer Science - Machine Learning, Computer Science - Artificial Intelligence, Computer Science - Neural and Evolutionary Computing
Abstract

In the quest for next-generation sequence modeling architectures, State Space Models (SSMs) have emerged as a potent alternative to transformers, particularly for their computational efficiency and suitability for dynamical systems. This paper investigates the effect of quantization on the S5 model to understand its impact on model performance and to facilitate its deployment to edge and resource-constrained platforms. Using quantization-aware training (QAT) and post-training quantization (PTQ), we systematically evaluate the quantization sensitivity of SSMs across different tasks like dynamical systems modeling, Sequential MNIST (sMNIST) and most of the Long Range Arena (LRA). We present fully quantized S5 models whose test accuracy drops less than 1% on sMNIST and most of the LRA. We find that performance on most tasks degrades significantly for recurrent weights below 8-bit precision, but that other components can be compressed further without significant loss of performance. Our results further show that PTQ only performs well on language-based LRA tasks whereas all others require QAT. Our investigation provides necessary insights for the continued development of efficient and hardware-optimized SSMs.

Published
2024

8. Concepts and Paradigms for Neuromorphic Programming

Author

Abreu, Steven

Subjects
Computer Science - Neural and Evolutionary Computing, Computer Science - Emerging Technologies
Abstract

The value of neuromorphic computers depends crucially on our ability to program them for relevant tasks. Currently, neuromorphic computers are mostly limited to machine learning methods adapted from deep learning. However, neuromorphic computers have potential far beyond deep learning if we can only make use of their computational properties to harness their full power. Neuromorphic programming will necessarily be different from conventional programming, requiring a paradigm shift in how we think about programming in general. The contributions of this paper are 1) a conceptual analysis of what "programming" means in the context of neuromorphic computers and 2) an exploration of existing programming paradigms that are promising yet overlooked in neuromorphic computing. The goal is to expand the horizon of neuromorphic programming methods, thereby allowing researchers to move beyond the shackles of current methods and explore novel directions.

Published
2023

9. Training a spiking neural network on an event-based label-free flow cytometry dataset

Author

Gouda, Muhammed, Abreu, Steven, Lugnan, Alessio, and Bienstman, Peter

Subjects
Computer Science - Neural and Evolutionary Computing, Computer Science - Computer Vision and Pattern Recognition, Computer Science - Emerging Technologies
Abstract

Imaging flow cytometry systems aim to analyze a huge number of cells or micro-particles based on their physical characteristics. The vast majority of current systems acquire a large amount of images which are used to train deep artificial neural networks. However, this approach increases both the latency and power consumption of the final apparatus. In this work-in-progress, we combine an event-based camera with a free-space optical setup to obtain spikes for each particle passing in a microfluidic channel. A spiking neural network is trained on the collected dataset, resulting in 97.7% mean training accuracy and 93.5% mean testing accuracy for the fully event-based classification pipeline., Comment: Accepted to Neuro-Inspired Computational Elements (NICE) conference by ACM in San Antonio, TX, USA, 2023

Published
2023

10. Automated Architecture Design for Deep Neural Networks

Author

Abreu, Steven

Subjects
Computer Science - Machine Learning, Computer Science - Neural and Evolutionary Computing, Statistics - Machine Learning
Abstract

Machine learning has made tremendous progress in recent years and received large amounts of public attention. Though we are still far from designing a full artificially intelligent agent, machine learning has brought us many applications in which computers solve human learning tasks remarkably well. Much of this progress comes from a recent trend within machine learning, called deep learning. Deep learning models are responsible for many state-of-the-art applications of machine learning. Despite their success, deep learning models are hard to train, very difficult to understand, and often times so complex that training is only possible on very large GPU clusters. Lots of work has been done on enabling neural networks to learn efficiently. However, the design and architecture of such neural networks is often done manually through trial and error and expert knowledge. This thesis inspects different approaches, existing and novel, to automate the design of deep feedforward neural networks in an attempt to create less complex models with good performance that take away the burden of deciding on an architecture and make it more efficient to design and train such deep networks., Comment: Undergraduate Thesis

Published
2019

13. Neuromorphic intermediate representation: A unified instruction set for interoperable brain-inspired computing

Author

Pedersen, Jens, Abreu, Steven, Jobst, Matthias, Lenz, Gregor, Fra, Vittorio, Bauer, Felix Christian, Muir, Dylan Richard, Zhou, Peng, Vogginger, Bernhard, Heckel, Kade, Urgese, Gianvito, Shankar, Sadasivan, Stewart, Terrence C., Sheik, Sadique, Eshraghian, Jason K., Pedersen, Jens, Abreu, Steven, Jobst, Matthias, Lenz, Gregor, Fra, Vittorio, Bauer, Felix Christian, Muir, Dylan Richard, Zhou, Peng, Vogginger, Bernhard, Heckel, Kade, Urgese, Gianvito, Shankar, Sadasivan, Stewart, Terrence C., Sheik, Sadique, and Eshraghian, Jason K.

Abstract

Spiking neural networks and neuromorphic hardware platforms that simulate neuronal dynamics are getting wide attention and are being applied to many relevant problems using Machine Learning. Despite a well-established mathematical foundation for neural dynamics, there exists numerous software and hardware solutions and stacks whose variability makes it difficult to reproduce findings. Here, we establish a common reference frame for computations in digital neuromorphic systems, titled Neuromorphic Intermediate Representation (NIR). NIR defines a set of computational and composable model primitives as hybrid systems combining continuous-time dynamics and discrete events. By abstracting away assumptions around discretization and hardware constraints, NIR faithfully captures the computational model, while bridging differences between the evaluated implementation and the underlying mathematical formalism. NIR supports an unprecedented number of neuromorphic systems, which we demonstrate by reproducing three spiking neural network models of different complexity across 7 neuromorphic simulators and 4 digital hardware platforms. NIR decouples the development of neuromorphic hardware and software, enabling interoperability between platforms and improving accessibility to multiple neuromorphic technologies. We believe that NIR is a key next step in brain-inspired hardware-software co-evolution, enabling research towards the implementation of energy efficient computational principles of nervous systems. NIR is available at neuroir.org, QC 20240926

Published
2024
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17. Hands-on reservoir computing: a tutorial for practical implementation

Author

Cucchi, Matteo, Abreu, Steven, Ciccone, Giuseppe, Brunner, Daniel, Kleemann, Hans, Cucchi, Matteo, Abreu, Steven, Ciccone, Giuseppe, Brunner, Daniel, and Kleemann, Hans

Abstract

This manuscript serves a specific purpose: to give readers from fields such as material science, chemistry, or electronics an overview of implementing a reservoir computing (RC) experiment with her/his material system. Introductory literature on the topic is rare and the vast majority of reviews puts forth the basics of RC taking for granted concepts that may be nontrivial to someone unfamiliar with the machine learning field (see for example reference Lukosevicius (2012 Neural Networks: Tricks of the Trade (Berlin: Springer) pp 659-686). This is unfortunate considering the large pool of material systems that show nonlinear behavior and short-term memory that may be harnessed to design novel computational paradigms. RC offers a framework for computing with material systems that circumvents typical problems that arise when implementing traditional, fully fledged feedforward neural networks on hardware, such as minimal device-to-device variability and control over each unit/neuron and connection. Instead, one can use a random, untrained reservoir where only the output layer is optimized, for example, with linear regression. In the following, we will highlight the potential of RC for hardware-based neural networks, the advantages over more traditional approaches, and the obstacles to overcome for their implementation. Preparing a high-dimensional nonlinear system as a well-performing reservoir for a specific task is not as easy as it seems at first sight. We hope this tutorial will lower the barrier for scientists attempting to exploit their nonlinear systems for computational tasks typically carried out in the fields of machine learning and artificial intelligence. A simulation tool to accompany this paper is available online 7 7 https://github.com/stevenabreu7/handson_reservoir..

Published
2023
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18. Neuromorphic Intermediate Representation: A Unified Instruction Set for Interoperable Brain-Inspired Computing

Author

Pedersen, Jens E., Abreu, Steven, Jobst, Matthias, Lenz, Gregor, Fra, Vittorio, Bauer, Felix C., Muir, Dylan R., Zhou, Peng, Vogginger, Bernhard, Heckel, Kade, Urgese, Gianvito, Shankar, Sadasivan, Stewart, Terrence C., Eshraghian, Jason K., Sheik, Sadique, Pedersen, Jens E., Abreu, Steven, Jobst, Matthias, Lenz, Gregor, Fra, Vittorio, Bauer, Felix C., Muir, Dylan R., Zhou, Peng, Vogginger, Bernhard, Heckel, Kade, Urgese, Gianvito, Shankar, Sadasivan, Stewart, Terrence C., Eshraghian, Jason K., and Sheik, Sadique

Abstract

Spiking neural networks and neuromorphic hardware platforms that emulate neural dynamics are slowly gaining momentum and entering main-stream usage. Despite a well-established mathematical foundation for neural dynamics, the implementation details vary greatly across different platforms. Correspondingly, there are a plethora of software and hardware implementations with their own unique technology stacks. Consequently, neuromorphic systems typically diverge from the expected computational model, which challenges the reproducibility and reliability across platforms. Additionally, most neuromorphic hardware is limited by its access via a single software frameworks with a limited set of training procedures. Here, we establish a common reference-frame for computations in neuromorphic systems, dubbed the Neuromorphic Intermediate Representation (NIR). NIR defines a set of computational primitives as idealized continuous-time hybrid systems that can be composed into graphs and mapped to and from various neuromorphic technology stacks. By abstracting away assumptions around discretization and hardware constraints, NIR faithfully captures the fundamental computation, while simultaneously exposing the exact differences between the evaluated implementation and the idealized mathematical formalism. We reproduce three NIR graphs across 7 neuromorphic simulators and 4 hardware platforms, demonstrating support for an unprecedented number of neuromorphic systems. With NIR, we decouple the evolution of neuromorphic hardware and software, ultimately increasing the interoperability between platforms and improving accessibility to neuromorphic technologies. We believe that NIR is an important step towards the continued study of brain-inspired hardware and bottom-up approaches aimed at an improved understanding of the computational underpinnings of nervous systems., Comment: NIR is available at https://github.com/neuromorphs/NIR

Published
2023

25. Interactions vestibulo-végétatives et évolution du baroréflexe carotidien au cours de deux modèles d'impesanteur : l'alitement prolongé tête déclive et l'immersion sèche

Author

Abreu, Steven de, Mobilités : Vieillissement, Pathologie, Santé (COMETE), Institut National de la Santé et de la Recherche Médicale (INSERM)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU), Normandie Université, and Hervé Normand

Subjects
Dry immersion, Réflexe vestibulo-sympathique, Déconditionnement cardio-vasculaire, Weightlessness, Orthostatisme, Cardiovascular deconditioning, Alitement anti-orthostatique, Vestibulo sympathetic reflex, Microgravité, Immersion sèche, Bed rest, Orthostatism, [SDV.MHEP]Life Sciences [q-bio]/Human health and pathology
Abstract

The removal of the gravity vector during spaceflight normally directed from the head to the feet in the standing position acts on the body fluids by the loss of the hydrostatic pressure gradient, which results in a cardiovascular deconditioning syndrome. This lack of gravity also disturbs the vestibular system, particularly otoliths that lose their ability to detect head tilts. We conducted our studies in humans using the 3-day dry immersion model and the 60-day anti-orthostatic bed rest model. The aim of our first research work is to study the influence of the otolithic system on the regulation of the cardiovascular system through the vestibulo-sympathetic reflex. For this purpose, galvanic stimulation experiments were used to evaluate otolithic sensitivity as well as neck flexion maneuvers associated with conventional cardiovascular and plethysmography measurements. In addition, an accelerometer has been used to quantify the activity and inactivity phases. The aim of our second research project is to study the evolution of the carotid baroreflex during weightlessness simulation models and to establish possible hypotheses of interaction with otolithic afferents. For this purpose, blood pressure and heart rate measurements were used in response to mechanical stimulations of carotid baroreceptors applied directly via the pressure collar technique. Our results confirmed that the neck flexion maneuver is indeed an otolithic stimulation with the appearance of otolitic changes of reactivity only in ventral decubitus and not in lateral decubitus. Nevertheless, the role of vestibulo-sympathetic reflex on cardiovascular regulation is not clearly demonstrated. Moreover, the sensitivity of the carotid baroreflex during these protocols is not modified. Our general hypothesis of a change in cardiovascular control related to the reduction of otolithic stimulation during weightless simulation protocols is not verified. It remains to understand the real meaning of the head-down neck flexion maneuver and its connection with the authentic otolithic stimulation it causes. It is likely that multiple sensory systems are involved in cardiovascular regulation in relation to gravity. The specific role of the vestibular system is likely to be better understood in situations where its plasticity is best brought into play, that is to say in real weightlessness.; La suppression du vecteur gravité lors des vols spatiaux normalement orienté de la tête vers les pieds en position debout agit sur les fluides de l’organisme par la perte du gradient de pression hydrostatique, ce qui aboutit à un syndrome de déconditionnement cardio-vasculaire. Cette absence de gravité perturbe également le système vestibulaire, particulièrement les otolithes qui perdent leur capacité à détecter les inclinaisons de la tête. Nous avons conduit nos études chez l’homme à l’aide du modèle d’immersion sèche durant 3 jours ainsi que du modèle d’alitement anti-orthostatique durant 60 jours.Le but de notre premier travail de recherche est d’étudier l’influence du système otolithique sur la régulation du système cardio-vasculaire au travers du réflexe vestibulo-sympathique. Il a pour cela été utilisé des expérimentations de stimulation galvanique pour évaluer la sensibilité otolithique ainsi que des manœuvres de flexion de cou associées à des mesures cardio-vasculaires conventionnelles et de pléthysmographie. Un accéléromètre a, de plus, été utilisé pour quantifier les phases d’activité et d’inactivité.Le but de notre second travail de recherche est d’étudier l’évolution du baroréflexe carotidien au cours des modèles de stimulation d’impesanteur et d’établir d’éventuelles hypothèses d’interaction avec les afférences otolithiques. Il a pour cela été utilisé des mesures de pression artérielle et de fréquence cardiaque en réponse à des stimulations mécaniques des barorécepteurs carotidiens appliquées de façon directe via la technique du collier de pression.Nos résultats ont confirmé que la manœuvre de flexion du cou est bien une stimulation otolithique avec l’apparition des modifications de réactivité otolitiques seulement en décubitus ventral et non en décubitus latéral. Néanmoins le rôle du réflexe vestibulo-sympathique sur la régulation cardio-vasculaire n’est pas clairement mis en évidence. Par ailleurs, la sensibilité du baroréflexe carotidien au cours de ces protocoles n’est pas modifiée.Notre hypothèse générale d’une modification du contrôle cardio-vasculaire en lien avec la réduction de la stimulation otolithique au cours de protocoles de simulation d’impesanteur n’est pas vérifiée. Il reste à comprendre la signification réelle de la manœuvre du head-down neck flexion et son lien avec l’authentique stimulation otolithique qu’elle provoque. Il est vraisemblable que de multiples systèmes sensoriels interviennent dans la régulation cardio-vasculaire en lien avec la gravité. Le rôle spécifique du système vestibulaire sera vraisemblablement mieux appréhendé dans des situations où sa plasticité est le mieux mise en jeu c’est-à-dire en impesanteur réelle.

Published
2019

26. Vestibular-vegetative interactions and evolution of carotid baroreflex in two models of weightlessness : prolonged head-down bed rest and dry immersion

Author

Abreu, Steven De and STAR, ABES

Subjects
Dry immersion, Réflexe vestibulo-sympathique, Déconditionnement cardio-vasculaire, [SDV.MHEP] Life Sciences [q-bio]/Human health and pathology, Weightlessness, Orthostatisme, Cardiovascular deconditioning, Alitement anti-orthostatique, Vestibulo sympathetic reflex, Microgravité, Immersion sèche, Bed rest, Orthostatism
Abstract

The removal of the gravity vector during spaceflight normally directed from the head to the feet in the standing position acts on the body fluids by the loss of the hydrostatic pressure gradient, which results in a cardiovascular deconditioning syndrome. This lack of gravity also disturbs the vestibular system, particularly otoliths that lose their ability to detect head tilts. We conducted our studies in humans using the 3-day dry immersion model and the 60-day anti-orthostatic bed rest model. The aim of our first research work is to study the influence of the otolithic system on the regulation of the cardiovascular system through the vestibulo-sympathetic reflex. For this purpose, galvanic stimulation experiments were used to evaluate otolithic sensitivity as well as neck flexion maneuvers associated with conventional cardiovascular and plethysmography measurements. In addition, an accelerometer has been used to quantify the activity and inactivity phases. The aim of our second research project is to study the evolution of the carotid baroreflex during weightlessness simulation models and to establish possible hypotheses of interaction with otolithic afferents. For this purpose, blood pressure and heart rate measurements were used in response to mechanical stimulations of carotid baroreceptors applied directly via the pressure collar technique. Our results confirmed that the neck flexion maneuver is indeed an otolithic stimulation with the appearance of otolitic changes of reactivity only in ventral decubitus and not in lateral decubitus. Nevertheless, the role of vestibulo-sympathetic reflex on cardiovascular regulation is not clearly demonstrated. Moreover, the sensitivity of the carotid baroreflex during these protocols is not modified. Our general hypothesis of a change in cardiovascular control related to the reduction of otolithic stimulation during weightless simulation protocols is not verified. It remains to understand the real meaning of the head-down neck flexion maneuver and its connection with the authentic otolithic stimulation it causes. It is likely that multiple sensory systems are involved in cardiovascular regulation in relation to gravity. The specific role of the vestibular system is likely to be better understood in situations where its plasticity is best brought into play, that is to say in real weightlessness., La suppression du vecteur gravité lors des vols spatiaux normalement orienté de la tête vers les pieds en position debout agit sur les fluides de l’organisme par la perte du gradient de pression hydrostatique, ce qui aboutit à un syndrome de déconditionnement cardio-vasculaire. Cette absence de gravité perturbe également le système vestibulaire, particulièrement les otolithes qui perdent leur capacité à détecter les inclinaisons de la tête. Nous avons conduit nos études chez l’homme à l’aide du modèle d’immersion sèche durant 3 jours ainsi que du modèle d’alitement anti-orthostatique durant 60 jours.Le but de notre premier travail de recherche est d’étudier l’influence du système otolithique sur la régulation du système cardio-vasculaire au travers du réflexe vestibulo-sympathique. Il a pour cela été utilisé des expérimentations de stimulation galvanique pour évaluer la sensibilité otolithique ainsi que des manœuvres de flexion de cou associées à des mesures cardio-vasculaires conventionnelles et de pléthysmographie. Un accéléromètre a, de plus, été utilisé pour quantifier les phases d’activité et d’inactivité.Le but de notre second travail de recherche est d’étudier l’évolution du baroréflexe carotidien au cours des modèles de stimulation d’impesanteur et d’établir d’éventuelles hypothèses d’interaction avec les afférences otolithiques. Il a pour cela été utilisé des mesures de pression artérielle et de fréquence cardiaque en réponse à des stimulations mécaniques des barorécepteurs carotidiens appliquées de façon directe via la technique du collier de pression.Nos résultats ont confirmé que la manœuvre de flexion du cou est bien une stimulation otolithique avec l’apparition des modifications de réactivité otolitiques seulement en décubitus ventral et non en décubitus latéral. Néanmoins le rôle du réflexe vestibulo-sympathique sur la régulation cardio-vasculaire n’est pas clairement mis en évidence. Par ailleurs, la sensibilité du baroréflexe carotidien au cours de ces protocoles n’est pas modifiée.Notre hypothèse générale d’une modification du contrôle cardio-vasculaire en lien avec la réduction de la stimulation otolithique au cours de protocoles de simulation d’impesanteur n’est pas vérifiée. Il reste à comprendre la signification réelle de la manœuvre du head-down neck flexion et son lien avec l’authentique stimulation otolithique qu’elle provoque. Il est vraisemblable que de multiples systèmes sensoriels interviennent dans la régulation cardio-vasculaire en lien avec la gravité. Le rôle spécifique du système vestibulaire sera vraisemblablement mieux appréhendé dans des situations où sa plasticité est le mieux mise en jeu c’est-à-dire en impesanteur réelle.

Published
2019

28. Drug provocation tests to identify analgesic alternatives for an infant with Stevens-Johnson syndrome caused by ibuprofen-acetaminophen.

Author

Abreu, Steven, Castelblanco-Arango, Iris Yansa, Gómez-Pineda, Paola Andrea, and Cardona, Ricardo

Abstract

Background: The Stevens-Johnson syndrome is a serious skin reaction to drugs, and it is potentially life-threatening. Its handling involves the strict restriction of the drug involved, as well as of the drugs that are similar or structurally related. Case report: A two-year and eight-month old girl with Stevens-Jonson syndrome that was caused by acetaminophen and ibuprofen. Due to the total restriction of non-steroidal anti-inflammatory drugs, and with the purpose of establishing antipyretic alternatives, an oral provocation test was carried out with the usual dose of oral nimesulide, which was negative for both immediate and late reactions. In order to offer a parenteral alternative, a provocation test was carried out with intravenous dipyrone, with in-hospital monitoring for 48 hours in an administration protocol of 10, 30 and 60 %; one dose per hour, for a total of 400 mg. The provocation test was negative for both immediate and late reactions. Oral nimesulide or parenteral dipyrone were prescribed upon requiring analgesic, anti-inflammatory, or antipyretic medication. Conclusion: At a pediatric age, febrile symptoms are common and controlling them is fundamental; such that if an allergy to non-steroidal anti-inflammatory drugs and acetaminophen is identified in an infant, an affectation on the quality of life will be entailed. [ABSTRACT FROM AUTHOR]

Published
2020
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30. Multi-System Deconditioning in 3-Day Dry Immersion without Daily Raise

Author

De Abreu, Steven, primary, Amirova, Liubov, additional, Murphy, Ronan, additional, Wallace, Robert, additional, Twomey, Laura, additional, Gauquelin-Koch, Guillemette, additional, Raverot, Veronique, additional, Larcher, Françoise, additional, Custaud, Marc-Antoine, additional, and Navasiolava, Nastassia, additional

Published
2017
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32. Arterial and venous cerebral blood flow responses to long‐term head‐down bed rest in male volunteers.

Author

Ogoh, Shigehiko, Sato, Kohei, Abreu, Steven, Denise, Pierre, and Normand, Hervé

Subjects
CEREBRAL circulation, INTERNAL carotid artery, POSTERIOR cerebral artery, BED rest, VERTEBRAL artery
Abstract

New Findings: What is the central question of this study?A heterogeneous cerebral blood flow (CBF) response in the cerebral arteries has been demonstrated in several physiological conditions, and it might be attributable to different physiological properties. However, the whole cerebral haemodynamic response to weightlessness remains unknown.What is the main finding and its importance?Long‐term head‐down bed rest caused a heterogeneous CBF response between the anterior and posterior cerebral arteries and between the cerebral arteries and veins. Especially, in contrast to the anterior cerebral circulation, the posterior arterial and venous CBFs were well maintained throughout weightlessness. In this study, we investigated the whole cerebral haemodynamic response to long‐term head‐down bed rest (HDBR). We hypothesized that long‐term exposure to weightlessness influences cerebral blood flow (CBF) or CBF distribution among cerebral arteries and veins because of the different physiological roles of each cerebral vessel. To test this hypothesis, 10 male volunteers were exposed to −6 deg HDBR for 60 days. Blood flows in the internal carotid artery, external carotid artery and vertebral artery or internal jugular vein and vertebral vein were measured using ultrasonography before and on days 30 and 57 of the HDBR. The internal carotid artery blood flow was reduced on day 30 (P = 0.019) and had returned to the baseline level by day 57. In contrast, the vertebral artery blood flow remained unaltered throughout the HDBR (P = 0.626). The internal jugular vein blood flow was reduced on day 30 (P = 0.009), whereas the vertebral vein blood flow remained unaltered (P = 0.397). These findings suggest that long‐term HDBR causes a heterogeneous CBF response between the anterior and posterior cerebral circulation in the both arteries and veins. The posterior arterial and venous CBFs were well maintained throughout HDBR, and these CBF responses to HDBR were different from the anterior cerebral circulation. [ABSTRACT FROM AUTHOR]

Published
2020
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33. The Alt-A Mortgage Problem? Too Many Rookies Making Loans

Author

Abreu, Steven M.

Subjects
Mortgages -- Analysis, Mortgages, Banking, finance and accounting industries, Business, Economics
Abstract

Recently there have been concerns about the alt-A mortgage market: lax underwriting standards, a propensity for borrowers to 'misstate' their incomes, and 'no doc' programs being used to mask qualification [...]

Published
2004

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