1,721,015 research outputs found
Effects of caffeine on sleep and wakefulness: an update
No full text[Book abstract:] Coffee, tea, and chocolate are among the most frequently consumed products in the world. The pleasure that many experience from these edibles is accompanied by a range of favorable and adverse effects on the brain that have been the focus of a wealth of recent research.Coffee, Tea, Chocolate, and the Brain presents new information on the long-debated issue about the beneficial and/or potentially negative effects on the brain of the consumption of coffee, tea, and chocolate. With caffeine as the common component in these beverages and food, this volume features important data on the effects of caffeine on sleep, memory, cognition, mood, performance, and more. It also contains specific information on new directions of research on the effect of caffeine on Parkinson’s disease, seizures, ischemia, the stress axis, and brain development. Debate on the potential addiction to caffeine is included, as well as discussion of how chocolate and caffeine can induce or alleviate various types of headaches.With contributions from world-renowned experts in the field, this up-to-date reference provides important information for scientists, researchers, industry professionals, and students involved in nutrition, neurology, neuropharmacology, clinical psychology, and other health-related sciences
Imagerie de perfusion des crises épileptiques temporo-limbiques: zones épileptogènes et non épileptogènes
No full textCoffee, caffeine, and cognitive performance
No full text[Book abstract:] Coffee, tea, and chocolate are among the most frequently consumed products in the world. The pleasure that many experience from these edibles is accompanied by a range of favorable and adverse effects on the brain that have been the focus of a wealth of recent research.Coffee, Tea, Chocolate, and the Brain presents new information on the long-debated issue about the beneficial and/or potentially negative effects on the brain of the consumption of coffee, tea, and chocolate. With caffeine as the common component in these beverages and food, this volume features important data on the effects of caffeine on sleep, memory, cognition, mood, performance, and more. It also contains specific information on new directions of research on the effect of caffeine on Parkinson’s disease, seizures, ischemia, the stress axis, and brain development. Debate on the potential addiction to caffeine is included, as well as discussion of how chocolate and caffeine can induce or alleviate various types of headaches.With contributions from world-renowned experts in the field, this up-to-date reference provides important information for scientists, researchers, industry professionals, and students involved in nutrition, neurology, neuropharmacology, clinical psychology, and other health-related sciences
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Perfusion imaging of temporo-limbic epileptic seizures,epileptogenic and non-epileptogenic zones
No full textPour évaluer l'apport du SPECT critique à la définition de la zone épileptogène (ZE) dans les épilepsies focales, nous avons étudié l'impact de la variabilité des paramètres cliniques et techniques sur le pattern de perfusion cérébrale, susceptibles d'expliquer des variations de débit sanguin cérébral (DSC) au-delà de la ZE.Dans le modèle d'embrasement de l'amygdale chez le rat, nous avons étudié les variations de DSC en fonction du délai d'injection du radiotraceur ([14C]-iodoantipyrine, IAP) et de la sévérité des crises, par rapport à un groupe témoin (DSC intercritique chez des animaux embrasés), lors de crises secondairement généralisées (CSG, n=26) et de crises focales (CF, n=19), dans 29 régions cérébrales d'intérêt, par la technique d'autoradiographie quantitative à l'IAP. Lors des CSG, seuls les temps d'injection critique précoce et post-critique ont permis la latéralisation et localisation grossière de la ZE, alors que des augmentations diffuses du DSC ont été observées en période critique. La transition de l'hyper vers l'hypoperfusion était observée lors de l'injection critique tardive. La localisation précise du foyer d'origine des crises a été obtenue lors de l'imagerie des CF les plus subtiles du l'embrasement (stade 0), alors que les CF de stade 1 s'accompagnaient déjà d'augmentations bilatérales et relativement étendues du DSC.Chez des patients avec une épilepsie mesio-temporale (EMT), nous avons étudié 26 paires de SPECT critique et intercritique, répartis en 3 groupes selon l'intensité de la sémiologie clinique lors du SPECT critique. D après l'étude individuelle des SPECT critique intercritique (SISCOM) et les analyses de groupes dans SPM, nous avons observé des patterns combinant hyper et hypoperfusion, d'étendue et de complexité croissantes en fonction de l'accentuation de la sémiologie critique. Dans les CF avec aura isolée, la lecture des SISCOM a permis la localisation correcte de la ZE chez 4/8 patients, alors que l'analyse de groupe n a montré aucune différence par rapport au groupe témoin, du fait des variations inter-individuelles, de la normalisation spatiale et des faibles variations de DSC. Dans les crises avec altération de la conscience et automatismes moteurs et dystonie, les analyses SISCOM et SPM ont montré une hyperperfusion temporale antéro-mésiale (concordante avec la ZE), s'étendant à l'insula, aux ganglions de la base et au thalamus dans le groupe avec dystonie. L'hypoperfusion critique intéressait des régions pré-frontales et pariétales, le gyrus cingulaire antérieur et postérieur, de façon plus marquée dans ce dernier groupe.L'analyse de nos études animales et humaine a montré une corrélation positive entre l'étendue spatiale des patterns de perfusion et la sévérité des crises, incluant le recrutement de régions sous-corticales à distance. Nous suggérons que les automatismes moteurs des crises mésio-temporales résultent de la mise au repos des régions hypoperfusées, dont le rôle dans l'intentionalité et la planification du mouvement est transitoirement suspendu sous l'effet de l'hyperactivation critique des régions temporo-limbiques.To assess the contribution of the ictal SPECT to the definition of the epileptogenic zone (EZ) prior to surgery in focal drug-resistant epilepsies, we investigated the effect of the variability of clinical and technical parameters upon patterns of perfusion, that could account for ictal cerebral blood flow (CBF) changes beyond the EZ. We studied CBF patterns in a rat model of amygdala-kindled seizures to assess the influence of the timing of injection of the tracer and the extent of seizure spread, with respect to a control group (interictal CBF measurements in kindled rats), during secondary generalized (SGS, n=26 fully-kindled rats) and focal seizures (FS, n=19 partially kindled rats), in 29 regions of interest, with the quantitative [14C]-iodoantipyrine autoradiographic method. During SGS, the correct lateralization and localization of the focus within limbic structures was only possible at early ictal and post-ictal times, in between we observed widespread rCBF increases. The switch from hyper to hypoperfusion was observed at the time of late ictal injection. The accurate localization of the EZ was obtained for the study of the more FS (stage 0). At stage 1 of the kindling, there was already widespread spreading of hyperperfusion. In humans, we studied 26 pairs of ictal and interictal SPECTs from patients with mesial temporal lobe epilepsy, classified in 3 groups according to the progression of ictal semiology. Using visual analysis of subtracted SPECTs (SISCOM) and group comparisons with a control group (using SPM), we observed more widespread combined hyper and hypoperfusion with the increasing complexity and duration of seizures at the time of the ictal SPECT. In the first group with motionless seizures, SISCOM analysis allowed correct localization of the focus in 4/8 patients, whereas SPM analysis failed to detect significant changes, due to individual variation, spatial normalization and small magnitude of CBF changes. In seizures with impairement of consciousness and automatisms (group 2) and dystonic posturing (group 3), SISCOM and SPM analysis showed antero-mesial temporal hyperperfusion (overlapping the EZ), extending to the insula, basal ganglia, and thalamus in the third group. Ictal hypoperfusion involved pre-frontal and parietal regions, the anterior and posterior cingulate gyri, with a greater extent in the 3rd group. In both human and animals studies, we observed a positive correlation between the spatial extent of composite patterns of hyper/hypoperfusion and the severity of seizures, as well as the recruitment of remote sub-cortical structures. We suggest that ictal purposeless human motor automatisms in MTLE results from the hypoactivity of the above mentioned set of hypoperfused areas, whose role in perceptual decision making and motor planning is transiently disrupted under the effect of hyperactive temporo-limbic structures
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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