351 research outputs found
The Role of Noninvasive Techniques in Stroke Therapy
Noninvasive techniques such as functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) have provided insight into understanding how neural connections are altered in consequence to cerebrovascular injury. The first part of this review will briefly survey some of the methodological issues and limitations related to noninvasive poststroke motor recovery studies. The second section will investigate some of the different neural mechanisms that underlie neurorehabilitation in stroke patients. The third part will explore our current understanding of motor memory processing, describe the neural structures that subserve motor memory consolidation, and discuss the current literature related to memory reconsolidation in healthy adults. Lastly, this paper will suggest the potential therapeutic applications of integrating noninvasive tools with memory consolidation and reconsolidation theories to enhance motor recovery. The overall objective of this work is to demonstrate how noninvasive technologies have been utilized in the multidisciplinary field of clinical behavioral neuroscience and to highlight their potential to be employed as clinical tools to promote individualized motor recovery in stroke patients
Sleep quality influences subsequent motor skill acquisition
While the influence of sleep on motor memory consolidation has been extensively investigated, its relation to initial skill acquisition is less well understood. The purpose of the present study was to investigate the influence of sleep quality and quantity on subsequent motor skill acquisition in young adults without sleep disorders. Fifty-five healthy adults (mean age = 23.8 years; 34 women) wore actigraph wristbands for 4 nights, which provided data on sleep patterns before the experiment, and then returned to the laboratory to engage in a motor sequence learning task (explicit 5-item finger sequence tapping task). Indicators of sleep quality and quantity were then regressed on a measure of motor skill acquisition (Gains Within Training, GWT). Wake After Sleep Onset (WASO; i.e., the total amount of time the participants spent awake after falling asleep) was significantly and negatively related to GWT. This effect was not because of general arousal level, which was measured immediately before the motor task. Conversely, there was no relationship between GWT and sleep duration or self-reported sleep quality. These results indicate that sleep quality, as assessed by WASO and objectively measured with actigraphy before the motor task, significantly impacts motor skill acquisition in young healthy adults without sleep disorders. (PsycINFO Database Record. (c) 2016 APA, all rights reserved).Accepted manuscrip
Simulation numérique d'agrégats fractals en milieu de microgravité
Depuis quelques dĂ©cennies, l'Ă©tude de l'agrĂ©gation fractale dans divers environnements est de plus en plus importante en raison de son omniprĂ©sence dans plusieurs domaines scientifiques. L'intĂ©rĂȘt est d'ailleurs marquĂ© dans les sciences de la microgravitĂ© oĂč les agrĂ©gats montrent des propriĂ©tĂ©s physiques trĂšs intĂ©ressantes. C'est dans cette optique que ce mĂ©moire s'attarde aux simulations informatiques reliĂ©es Ă l'agrĂ©gation de particules en microgravitĂ©. Tout d'abord, la thĂ©orie entourant les fractales ainsi que les simulations numĂ©riques concernant l'agrĂ©gation a Ă©tĂ© abordĂ©e. La description des algorithmes numĂ©riques dĂ©veloppĂ©s pour le projet est faite et les rĂ©sultats recueillis Ă partir de ceux-ci sont exposĂ©s. Une rigoureuse analyse est ensuite prĂ©sentĂ©e Ă partir des agrĂ©gats simulĂ©s. Dans cette Ă©tude, diffĂ©rents modĂšles numĂ©riques d'agrĂ©gation de particules, favorisant une vitesse de simulation relativement Ă©levĂ©e, sont dĂ©crits. De plus, les diffĂ©rents facteurs influençant l'agrĂ©gation de particules y sont analysĂ©s. Des explications aux phĂ©nomĂšnes physiques sont suggĂ©rĂ©es et des commentaires sont faits au sujet des algorithmes numĂ©riques afin d'optimiser la simulation d'agrĂ©gats dans des travaux futurs
Impact de l'orientation des fibres sur les comportements en traction, en flexion et en cisaillement d'un béton renforcé de fibres métalliques
RĂSUMĂ Le bĂ©ton renforcĂ© de fibres (BRF) est un matĂ©riau de construction en plein dĂ©veloppement depuis les annĂ©es 1990. Plusieurs travaux de recherche ont permis de mettre en Ă©vidence les avantages de ce matĂ©riau composite, tel que lâaugmentation des rĂ©sistances post-fissuration, lâaugmentation de la ductilitĂ© ainsi que lâaugmentation de la durabilitĂ© (ACI Committee 544, 2002; Desmettre & Charron, 2012; MC2010, 2010). MalgrĂ© les nombreux avantages du BRF, ce matĂ©riau demeure encore peu utilisĂ© de nos jours dans la pratique nord-amĂ©ricaine. Ceci est principalement dĂ» Ă lâabsence de recommandations dans les normes pour la conception dâĂ©lĂ©ments en BRF. En effet, les normes nord-amĂ©ricaines ne permettent pas de considĂ©rer lâapport des fibres dans le dimensionnement.----------ABSTRACT Since the 1990s, fiber reinforced concrete (FRC) is a building material in full development. Several researches have highlighted benefits of this composite material, such as the increase in post-crack resistance, ductility and durability (ACI Committee 544, 2002; Desmettre & Charron, 2012; MC2010, 2010). Despite its benefits, this material is still not widely used in North American practice nowadays. This is mainly due to the lack of recommendations in the standards for the design of FRC elements. Indeed, the North American standards do not allow to consider the fibers contribution in design
Motor Sequence Learning and Consolidation in Unilateral De Novo Patients with Parkinson's Disease
Previous research investigating motor sequence learning (MSL) and consolidation in patients with Parkinson's disease (PD) has predominantly included heterogeneous participant samples with early and advanced disease stages; thus, little is known about the onset of potential behavioral impairments. We employed a multisession MSL paradigm to investigate whether behavioral deficits in learning and consolidation appear immediately after or prior to the detection of clinical symptoms in the tested (left) hand. Specifically, our patient sample was limited to recently diagnosed patients with pure unilateral PD. The left hand symptomatic (LH-S) patients provided an assessment of performance following the onset of clinical symptoms in the tested hand. Conversely, right hand affected (left hand asymptomatic, LH-A) patients served to investigate whether MSL impairments appear before symptoms in the tested hand. LH-S patients demonstrated impaired learning during the initial training session and both LH-S and LH-A patients demonstrated decreased performance compared to controls during the next-day retest. Critically, the impairments in later learning stages in the LH-A patients were evident even before the appearance of traditional clinical symptoms in the tested hand. Results may be explained by the progression of disease-related alterations in relevant corticostriatal networks.status: publishe
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The role of noninvasive techniques in stroke therapy.
Noninvasive techniques such as functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) have provided insight into understanding how neural connections are altered in consequence to cerebrovascular injury. The first part of this review will briefly survey some of the methodological issues and limitations related to noninvasive poststroke motor recovery studies. The second section will investigate some of the different neural mechanisms that underlie neurorehabilitation in stroke patients. The third part will explore our current understanding of motor memory processing, describe the neural structures that subserve motor memory consolidation, and discuss the current literature related to memory reconsolidation in healthy adults. Lastly, this paper will suggest the potential therapeutic applications of integrating noninvasive tools with memory consolidation and reconsolidation theories to enhance motor recovery. The overall objective of this work is to demonstrate how noninvasive technologies have been utilized in the multidisciplinary field of clinical behavioral neuroscience and to highlight their potential to be employed as clinical tools to promote individualized motor recovery in stroke patients.Peer Reviewe
Dynamical Mass Estimates of the Pictoris Planetary System Through Gaussian Process Stellar Activity Modelling
Nearly 15 years of radial velocity (RV) monitoring and direct imaging enabled
the detection of two giant planets orbiting the young, nearby star
Pictoris. The Scuti pulsations of the star, overwhelming planetary
signals, need to be carefully suppressed. In this work, we independently
revisit the analysis of the RV data following a different approach than in the
literature to model the activity of the star. We show that a Gaussian Process
(GP) with a stochastically driven damped harmonic oscillator kernel can model
the Scuti pulsations. It provides similar results as parametric models
but with a simpler framework, using only 3 hyperparameters. It also enables to
model poorly sampled RV data, that were excluded from previous analysis, hence
extending the RV baseline by nearly five years. Altogether, the orbit and the
mass of both planets can be constrained from RV only, which was not possible
with the parametric modelling. To characterize the system more accurately, we
also perform a joint fit of all available relative astrometry and RV data. Our
orbital solutions for Pic b favour a low eccentricity of
and a relatively short period of
yr. The orbit of Pic c is eccentric with with
a period of yr. We find model-independent masses of
and M for Pic b and c, respectively, assuming
coplanarity. The mass of Pic b is consistent with the hottest start
evolutionary models, at an age of Myr. A direct direction of
Pic c would provide a second calibration measurement in a coeval system.Comment: 25 pages, 18 figures, Accepted to AJ, Typos Correcte
WEIRD: Wide-orbit Exoplanet search with InfraRed Direct imaging
We report results from the Wide-orbit Exoplanet search with InfraRed Direct
imaging (WEIRD), a survey designed to search for Jupiter-like companions on
very wide orbits (1000 to 5000 AU) around young stars (120 Myr) that are
known members of moving groups in the solar neighborhood (70 pc). Sharing
the same age, distance, and metallicity as their host while being on large
enough orbits to be studied as "isolated" objects make such companions prime
targets for spectroscopic observations and valuable benchmark objects for
exoplanet atmosphere models. The search strategy is based on deep imaging in
multiple bands across the near-infrared domain. For all 177 objects of our
sample, , , [3.6] and [4.5] images were obtained with
CFHT/MegaCam, GEMINI/GMOS, CFHT/WIRCam, GEMINI/Flamingos-2, and /IRAC.
Using this set of 4 images per target, we searched for sources with red
and colors, typically reaching good completeness
down to 2Mjup companions, while going down to 1Mjup for some targets, at
separations of AU. The search yielded 4 candidate companions with
the expected colors, but they were all rejected through follow-up proper motion
observations. Our results constrain the occurrence of 1-13 Mjup planetary-mass
companions on orbits with a semi-major axis between 1000 and 5000 AU at less
than 0.03, with a 95\% confidence level.Comment: 55 pages, 16 figures, accepted to A
The challenge of mapping the human connectome based on diffusion tractography
Tractography based on non-invasive diffusion imaging is central to the study of human brain connectivity. To date, the approach has not been systematically validated in ground truth studies. Based on a simulated human brain data set with ground truth tracts, we organized an open international tractography challenge, which resulted in 96 distinct submissions from 20 research groups. Here, we report the encouraging finding that most state-of-the-art algorithms produce tractograms containing 90% of the ground truth bundles (to at least some extent). However, the same tractograms contain many more invalid than valid bundles, and half of these invalid bundles occur systematically across research groups. Taken together, our results demonstrate and confirm fundamental ambiguities inherent in tract reconstruction based on orientation information alone, which need to be considered when interpreting tractography and connectivity results. Our approach provides a novel framework for estimating reliability of tractography and encourages innovation to address its current limitations
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