58 research outputs found
Réponse auditive oscillatoire chez le non-voyant : investigation par magnétoencéphalographie
Les personnes non-voyantes montrent dans les diffĂ©rents aspects de leurs vies quâelles sont capables de sâadapter Ă la privation visuelle en utilisant les capacitĂ©s intactes comme lâouĂŻ ou le toucher. Elles montrent quâelles peuvent bien Ă©voluer dans leur environnement en absence de vision et dĂ©montrent mĂȘme des fois des habiletĂ©s supĂ©rieures Ă celles des personnes voyantes. La recherche de ces derniĂšres dĂ©cennies sâest beaucoup intĂ©ressĂ©e aux capacitĂ©s adaptatives des non-voyants surtout avec lâavĂšnement des nouvelles techniques dâimagerie qui ont permis dâinvestiguer des domaines qui ne lâĂ©taient pas ou lâĂ©taient difficilement avant.
Les capacitĂ©s supĂ©rieures des non voyants dans lâutilisation plus efficace des informations auditives et tactiles semblent avoir leur base neuronale dans le dans le cortex visuel dĂ©saffĂ©rentĂ©, qui continu Ă ĂȘtre fonctionnel aprĂšs la privation sensorielle et sâen trouve recrutĂ© pour le traitement de stimulations dites intermodales : auditives, tactiles et mĂȘme montre une implication dans des processus de plus haut niveau, comme la mĂ©moire ou le langage. Cette implication fonctionnelle intermodale rĂ©sulte de la plasticitĂ© du cortex visuel c'est-Ă -dire sa capacitĂ© Ă changer sa structure, sa fonction et dâadapter ses interactions avec les autres systĂšmes en lâabsence de vision. La plasticitĂ© corticale nâest pas exclusive au cortex visuel mais est un Ă©tat permanent de tout le cerveau.
Pour mesurer lâactivitĂ© du cortex visuel des non voyants, une mesure dâexcitabilitĂ© de ses neurones consiste Ă mesurer le temps de recouvrement de lâonde N1 en potentiels Ă©voquĂ©s, qui est plus rapide chez les non voyants dans la modalitĂ© auditive. En effet, les rĂ©ponses en potentiels et champs Ă©voquĂ©s ont Ă©tĂ© utilisĂ©s en EEG/MEG pour mettre en Ă©vidence des changements plastiques dans le cortex visuel des non-voyants pour le traitement de stimuli dans les modalitĂ©s auditives et tactiles. Ces rĂ©ponses Ă©taient localisĂ©es dans les rĂ©gions postĂ©rieures chez les non voyants contrairement aux contrĂŽles voyants. Un autre type de rĂ©ponse auditive a reçu moins dâintĂ©rĂȘt dans la recherche concernant la rĂ©organisation fonctionnelle en relation avec la privation sensorielle, il sâagit de la rĂ©ponse auditive oscillatoire (Auditory Steady-State Response ASSR). Câest une rĂ©ponse qui a lâavantage dâosciller au rythme de stimulation et dâĂȘtre caractĂ©risĂ© par une rĂ©ponse des aires auditives Ă©tiquetĂ©e Ă la frĂ©quence de stimulation. Cette Ă©tiquette se prĂ©sente sous la forme quâun pic dâĂ©nergie spectrale important qui culmine aux frĂ©quences prĂ©sentes dans la stimulation. Elle a Ă©galement lâavantage dâĂȘtre localisĂ©e dans les rĂ©gions auditives primaires, de lĂ tout changement de localisation de cette rĂ©ponse chez des non voyants en faveur des rĂ©gions visuelles pourrait ĂȘtre considĂ©rĂ© comme une Ă©vidence de la rĂ©organisation fonctionnelle qui sâopĂšre aprĂšs une privation sensorielle prĂ©coce. Le but de cette thĂšse est donc dâutiliser la rĂ©ponse oscillatoire Ă lâĂ©coute des sons modulĂ©s en amplitude (MA) pour mettre en Ă©vidence les corrĂ©lats de la rĂ©organisation fonctionnelle dans le cortex visuel des non-voyants prĂ©coces. La modulation de la rĂ©ponse auditive dans les rĂ©gions visuelles nous permettra de montrer quâune rĂ©organisation est possible chez les non-voyants pour ce traitement intermodal.
La premiĂšre Ă©tude est une validation du paradigme expĂ©rimental «frequency tagged sounds». Il sâagit de montrer quâune tĂąche de dĂ©tection de changement dans la stimulation, permet de moduler la rĂ©ponse ASSR aux sons modulĂ©s en amplitude en vue de lâutiliser dans les Ă©tudes chez les non voyants et dans les conditions dâune privation visuelle transitoire (avec les yeux bandĂ©s). Un groupe de sujets voyants ont rĂ©alisĂ© une tĂąche de dĂ©tection de changement dans la stimulation les yeux ouverts dans deux conditions : Ă©coute active qui consiste Ă dĂ©tecter un changement dans la frĂ©quence porteuse de la modulation en appuyant avec lâindex droit sur un bouton de rĂ©ponse et une condition dâĂ©coute passive. Les sons Ă©taient prĂ©sentĂ©s en Ă©coute monaurale et dichotique. Les rĂ©sultats ont montrĂ© une diffĂ©rence significative Ă lâoccurrence du changement dans la stimulation en Ă©coute dichotique seulement. Les schĂ©mas de plus grande rĂ©ponse controlatĂ©rale et de suppression binaurale dĂ©crit dans la littĂ©rature ont Ă©tĂ© confirmĂ©s.
La deuxiĂšme Ă©tude avait pour but de mettre en Ă©vidence une rĂ©organisation rapide de la rĂ©ponse ASSR chez un groupe de sujets voyants dans les conditions de privation visuelle transitoire de courte durĂ©e, par bandage des yeux pendant six heures. Le mĂȘme protocole expĂ©rimental que la premiĂšre Ă©tude a Ă©tĂ© utilisĂ© en Ă©coute active seulement. Les rĂ©sultats montrent que dans ces conditions une modulation de la rĂ©ponse corticale en Ă©coute dichotique dans les rĂ©gions visuelles est possible. Ces sources dâactivitĂ© occipitale adoptent une propriĂ©tĂ© du cortex auditif qui est le battement binaural, c'est-Ă -dire lâoscillation de la rĂ©ponse ASSR Ă la diffĂ©rence des frĂ©quences prĂ©sentĂ©es dans chaque oreille. Cet effet est prĂ©sent chez la moitiĂ© des sujets testĂ©s. La reprĂ©sentation corticale des sources occipitales Ă©volue durant la pĂ©riode de privation et montre un dĂ©placement des sources dâactivitĂ© dans la direction antĂ©ropostĂ©rieure Ă la fin de la pĂ©riode de privation.
La troisiĂšme Ă©tude a permis de comparer le traitement de la rĂ©ponse ASSR dans un groupe de non-voyants congĂ©nitaux Ă un groupe de voyants contrĂŽles, pour investiguer les corrĂ©lats de la rĂ©organisation fonctionnelle de cette rĂ©ponse aprĂšs une privation sensorielle de longue durĂ©e c'est-Ă -dire chez des non voyants congĂ©nitaux. Les rĂ©sultats montrent des diffĂ©rences significatives dans la reprĂ©sentation spectrale de la rĂ©ponse entre les deux groupes avec nĂ©anmoins des activations temporales importantes aussi bien chez les non voyants que chez les contrĂŽles voyants. Des sources distribuĂ©es ont Ă©tĂ© localisĂ©es dans les rĂ©gions associatives auditives dans les deux groupes Ă la diffĂ©rence des non voyants oĂč il y avait en plus lâimplication des rĂ©gions temporales infĂ©rieures, connues comme Ă©tant activĂ©es par la vision des objets chez les voyants et font partie de la voie visuelle du quoi.
Les rĂ©sultats prĂ©sentĂ©s dans le cadre de cette thĂšse vont dans le sens dâune rĂ©organisation rapide de la rĂ©ponse auditive oscillatoire aprĂšs une privation visuelle transitoire de courte durĂ©e par lâimplication des rĂ©gions visuelles dans le traitement de la rĂ©ponse ASSR par lâintermĂ©diaire du dĂ©masquage de connections existantes entre le cortex visuel et le cortex auditif. La privation visuelle de longue durĂ©e, elle conduit Ă des changements plastiques, dâune part intra modaux par lâextension de lâactivitĂ© aux rĂ©gions temporales supĂ©rieures et mĂ©dianes. Dâautre part, elle induit des changements inter modaux par lâimplication fonctionnelle des rĂ©gions temporales infĂ©rieures visuelles dans le traitement des sons modulĂ©s en amplitude comme objets auditifs alors quâelles sont normalement dĂ©diĂ©es au traitement des objets visuels. Cette rĂ©organisation passe probablement par les connections cortico-corticales.Blind persons show in their everyday life that they can efficiently adapt to visual deprivation by relying on their spared senses like touch or the sense of hearing. They also show they can challenge their environment without vision and sometimes even demonstrate superior abilities compared to sighted counterparts. In the last decades, research got more interested in adaptive capabilities of the blinds especially with the advent of new imaging techniques which made it possible to make giant steps investigating new avenues in the field of brain plasticity after sensory loss.
The superior abilities of blind individuals take the form of a more efficient use of auditory and tactile information and find their neuronal correlates in the deafferented visual cortex. The visual cortex of the blind is still highly functional after visual deprivation and is recruited for the processing of cross modal auditory and tactile stimulations. It can even show implication in higher level memory or language processes. This functional involvement results from the plasticity of the visual cortex which is its ability to change its structure, its function and to adapt its interactions with the other systems in the absence of vision. Cortical plasticity is not exclusive to the visual cortex of the blind but is a permanent state of the brain.
To appreciate cortical activity in the visual cortex of blind individuals, a measure of excitability of its neurons is used. This measure is represented by the recovery of the N1 component in ERPs to target detection, which is shorter in the auditory modality for the blind. Evoked potentials and evoked fields components in EEG and MEG have been shown to be reorganized in favour of the visual cortex of blind individuals compared to sighted ones for the auditory and tactile modalities. Posterior location for such components was found in the blind. The auditory steady-state response is another brain response that received less interest in the study of cortical reorganization after sensory loss. The ASSR has the advantage of oscillating at the stimulation rhythm and is characterized by a response in the auditory cortices tagged to the stimulation frequencies. The tag takes the form of an important spectral energy peak at the frequencies of stimulation in auditory areas. The ASSR is localized in left and right primary auditory areas, with this regard any posterior shift in the location of source activity in blind individuals also tagged to stimulation frequencies would be considered as an evidence of functional reorganization following sensory deprivation. The objectives of this work are to make use of the characteristics of the ASSR to amplitude modulated tones (AM) to investigate neural correlates of cross modal functional reorganization in the visual cortex of the blind for the processing of AM tones.
The first study is a validation of the frequency tagging paradigm. A change detection auditory task can modulate the envelope amplitude of the ASSR response. The same paradigm is used to investigate cross modal reorganisation after long and short term visual deprivation. In this first study a group of healthy sighted individuals detected a change in the carrier frequency of AM tones, with eyes opened during monaural and dichotic listening. Two conditions were tested an active condition where they had to press a button each time they hear the change and a passive condition. Results show a significant increase in the envelope amplitude of the ASSR to the onset of the carrier frequency change, only for dichotic presentation. Patterns of activations of the ASSR were maintained, with larger responses in the hemisphere contralateral to the stimulated ear and binaural suppression for the ipsilateral inputs for the dichotic presentation.
The second study was aimed to show that rapid changes in the ASSR to amplitude modulated tones (MA) are possible after short term sensory deprivation, by blindfolding sighted individuals for six hours. The same detection task was used but not the passive condition. Results show a modulation of the dichotic response in visual areas. The occipital source activity found, showed an auditory property as a binaural beat, which means an oscillating ASSR at a frequency equal to the difference of the frequencies presented to each ear. This effect was present in half of the participants and took place at the end of the blindfolding time. Cortical representation of the occipital sources showed a displacement of source activities in the antero-posterior direction at the end of transitory deprivation period.
In the third study we compared the ASSR processing between early blind individuals (congenitally blind) group and healthy sighted controls group, to investigate the neural correlates of functional reorganization of this response after long term visual deprivation. Results show significant differences in the spectral representation of the response between the two groups. Important auditory temporal activations were found in the two groups. Distributed sources were localized in primary and secondary auditory areas for the two groups. A difference was found in blind individuals who showed additional activations of inferior temporal areas, known to be activated by objects vision in sighted individuals and being part of the what visual pathway.
The results presented here are in line with a rapid reorganization of the ASSR after short term visual deprivation, and the implication of visual areas in the processing of AM tones for long term sensory deprivation in the congenitally blind. This was made possible by the unmasking of existing connections between auditory and visual cortices. Long term deprivation leads to plastic changes, in the auditory modality as a first step by the extension of activity to superior and middle temporal areas, then to cross modal changes with the functional involvement of inferior temporal areas in the processing of AM tones, considered as visual objects. This reorganization is likely to be mediated through lateral cortico-cortical connections
Phenolic profile and in vitro bioactive potential of Saharan Juniperus phoenicea L. and Cotula cinerea (Del) growing in Algeria
The aim of this study was to characterize the individual phenolic proïŹle and antioxidant, anti-inïŹammatory, cytotoxic, and antimicrobial activities of hydroethanolic and infusion extracts prepared from Algerian Saharan Juniperus phoenicea L. and Cotula cinerea (Del). The phenolic proïŹle was determined using a liquid chromatograph coupled to a diode array detector and an electrospray ionization mass spectrometer (LC-DAD-ESI/MS). A total of thirteen and nine individual phenolic compounds were identiïŹed in J. phoenicea and C. cinerea, respectively. 3-p-Coumaroylquinic acid, quercetin- and myricetin-O-pentoside were the major compounds present in J. phoenicea; on the other hand, C. cinerea presented luteolin-7-O-glucoside, luteolin-O-malonylhexoside, and 5-O-caïŹeoylquinic acid as the main molecules. In general, all samples exhibited interesting antioxidant activity when compared to the standard Trolox, but J. phoenicea extracts presented the highest bioactivity. Likewise, all the samples exhibited anti-inïŹammatory activity; thus J. phoenicea hydroethanolic extracts showed the highest potential (88 ± 8 ”g mLâ1). In addition, their cytotoxicity was evaluated towards a panel of four selected cell lines (HeLa, NCI-H460, MCF-7 and HepG2), and all the extracts showed cytotoxic eïŹects, with J. phoenicea extracts being the most eïŹective. The in vitro antimicrobial activity of the plant extracts was moderate, Gram-positive bacteria thus being more sensitive than the Gram-negative strains (MIC values between 5 and 20 mg mLâ1). The present work suggests that J. phoenicea and C. cinerea are sources of bioactive ingredients with potential use in the food and pharmaceutical industries.The authors are grateful to the Foundation for Science and
Technology (FCT, Portugal) and FEDER under Program PT2020
for financial support to CIMO (UID/AGR/00690/2013) through
L. Barros and R. Calhelha contracts. The authors are also grateful
to the FEDER-Interreg España-Portugal programme for
financial support through the project 0377_Iberphenol_6_E.info:eu-repo/semantics/publishedVersio
A theory of ferromagnetism in planar heterostructures of (Mn,III)-V semiconductors
A density functional theory of ferromagnetism in heterostructures of compound
semiconductors doped with magnetic impurities is presented. The variable
functions in the density functional theory are the charge and spin densities of
the itinerant carriers and the charge and localized spins of the impurities.
The theory is applied to study the Curie temperature of planar heterostructures
of III-V semiconductors doped with manganese atoms. The mean-field,
virtual-crystal and effective-mass approximations are adopted to calculate the
electronic structure, including the spin-orbit interaction, and the magnetic
susceptibilities, leading to the Curie temperature. By means of these results,
we attempt to understand the observed dependence of the Curie temperature of
planar -doped ferromagnetic structures on variation of their
properties. We predict a large increase of the Curie Temperature by additional
confinement of the holes in a -doped layer of Mn by a quantum well.Comment: 8 pages, 7 figure
Differential effects of speech and Language therapy and rTMS in chronic versus subacute post-stroke aphasia: Results of the NORTHSTAR-CA trial
Background & objective: Contralesional 1-Hz repetitive transcranial magnetic stimulation (rTMS) over the right pars triangularis combined with speech-language therapy (SLT) has shown positive results on the recovery of naming in subacute (5â45 days) post-stroke aphasia. NORTHSTAR-CA is an extension of the previously reported NORTHSTAR trial to chronic aphasia (\u3e6 months post-stroke) designed to compare the effectiveness of the same rTMS protocol in both phases. Methods: Sixty-seven patients with left middle cerebral artery infarcts (28 chronic, 39 subacute) were recruited (01-2014 to 07-2019) and randomized to receive rTMS (N = 34) or sham stimulation (N = 33) with SLT for 10 days. Primary outcome variables were Z-score changes in naming, semantic fluency and comprehension tests and adverse event frequency. Intention-to-treat analyses tested between-group effects at days 1 and 30 post-treatment. Chronic and subacute results were compared. Results: Adverse events were rare, mild, and did not differ between groups. Language outcomes improved significantly in all groups irrespective of treatment and recovery phase. At 30-day follow-up, there was a significant interaction of stimulation and recovery phase on naming recovery (P \u3c.001). Naming recovery with rTMS was larger in subacute (Mdn = 1.91/IQR =.77) than chronic patients (Mdn =.15/IQR = 1.68/P =.015). There was no significant rTMS effect in the chronic aphasia group. Conclusions: The addition of rTMS to SLT led to significant supplemental gains in naming recovery in the subacute phase only. While this needs confirmation in larger studies, our results clarify neuromodulatory vs training-induced effects and indicate a possible window of opportunity for contralesional inhibitory stimulation interventions in post-stroke aphasia. NORTHSTAR trial registration: https://clinicaltrials.gov/ct2/show/NCT02020421
Laser spectroscopy of rare earth compounds
SIGLEAvailable from British Library Document Supply Centre- DSC:D87201 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Laser spectroscopy of rare earth compounds
SIGLEAvailable from British Library Document Supply Centre- DSC:D87201 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Caractéristiques et modalités de prise en charge des enfants admis à la salle d'accueil des urgences vitales pédiatriques à l'HÎpital Louis Mourier
Cette thĂšse prĂ©sente une Ă©tude descriptive des caractĂ©ristiques et modalitĂ©s d'accueil de 148 enfants admis Ă la salle d'accueil des urgences vitales (SAUV) pĂ©diatriques du CHU Louis Mourier Ă Colombes (92), de 1997 Ă 2003. La population Ă©trangĂšre reprĂ©sente 54.05% dont trois quarts sont d'origine maghrĂ©bine. Le principal facteur de risque est le bas Ăąge : 82% des enfants ont moins de 5 ans et 53.36% ont moins d'un an. Les autres facteurs de risque sont : le sexe masculin ; le faible niveau socioĂ©conomique ; l'absence de suivi mĂ©dical ; le retard Ă la consultation ; les Ă©pidĂ©mies hivernales de bronchiolite Ă VRS (virus respiratoire syncitial) ; la pathologie elle-mĂȘme du fait de la difficultĂ© Ă apprĂ©cier la gravitĂ© des signes de dĂ©tresse respiratoire ou de son Ă©volution vers de graves complications. En l'absence de service de chirurgie pĂ©diatrique sur le site, les pathologies chirurgicales ne reprĂ©sentant que 5% des cas Ă©tudiĂ©s. La pathologie mĂ©dicale est prĂ©dominante (95% des cas) dont 41.21% de pathologies d'origine respiratoire et 22.3% de pathologies d'origine neurologique. La prise en charge est rapide et dure en moyenne 3 heures. L'intubation concerne surtout les bronchiolites (50% sont intubĂ©s). Le mortalitĂ©, dont la principale cause est la mort subite du nourrisson (MSN), ne concerne que 5 enfants. Les transferts sont assurĂ©s par le SMUR pĂ©diatrique et se font essentiellement vers les services de rĂ©animation des hĂŽpitaux pĂ©diatriques. La prĂ©vention passe par l'Ă©ducation et l'information du bassin de vie. Elle doit commencer dĂšs la maternitĂ© et doit ĂȘtre continue et complĂ©mentaire entre les professionnels de santĂ© mĂ©dicaux et paramĂ©dicaux dans les diffĂ©rentes structures.PARIS7-Xavier Bichat (751182101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF
Nuclear quadruple holeburning in preparation-dependent EuVO4
This paper reports on the study of EuVO4 samples grown from different fluxes. It is the first application of optical holeburning to investigate preparation-dependency between defect lines in samples of nominally the same compound. Analysis suggests that very few of the defect lines are common to the different growths
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