1,720,967 research outputs found
Discharge threshold is enhanced for several seconds after a single interictal spike in a model of focal epileptogenesis
Full text linkInterictal spikes (ISs) are typically observed between seizures in focal epilepsies. Whether ISs are causally involved or represent protective elements in the transition toward an ictal discharge is an open question. Previous studies suggested that inhibition or disfacilitation occurs during the period elapsing between two ISs induced by local application of either bicuculline or penicillin in the piriform cortex of the in vitro isolated guinea pig brain preparation. We further investigated this issue by studying responses to afferent stimulation during the interspike period (6.3 +/- 2.5 s; mean +/- SD). Properly set stimulation intensity of the lateral olfactory tract resets ISs exclusively (and not before) 4-10 s (5.6 +/- 2.0 s; mean +/- SD) after a preceding spontaneous spike. This finding demonstrates the existence of a period of enhanced threshold to stimulus-evoked activation that coincides with the interspike interval in the absence of stimulation. Current source density analysis of depth laminar profiles demonstrated that both stimulus-evoked and spontaneous ISs were generated by the activation of an identical cortical circuit. Our study suggests that interictal spiking could play a protective role or at least provide an effective restraint against the onset of a focal ictal discharge
Arterial supply of limbic structures in the guinea pig.
Full text linkThis study outlines the vascular territories of the cerebral arteries that originate from the Willis circle to supply limbic structures in the guinea pig brain. The entire cerebral vascular system was visualized in four preliminary experiments by performing superselective microangiographic studies with iodine contrast medium perfusion of the whole brain after in vitro isolation according to a technique described previously (de Curtis et al. [1991] Hippocampus 1:341-354). Subsequently, the perfusion territory of the different arteries that originate from the Willis circle was characterized after cannulation and perfusion of individual arteries with a gelatin solution that contained waterproof black ink. The analysis was performed by identifying the brain regions that contained the black stain on 150-microm-thick coronal sections that were cut after brain fixation with paraformaldehyde for at least 1 week. The middle cerebral artery and the rostral and caudal posterior cerebral arteries supply the limbic cortices and some related subcortical regions. In particular, large portions of the hippocampal formation are supplied by both the rostral posterior cerebral artery and the rostral branch of the caudal posterior cerebral artery, whereas the ventral temporal part of the hippocampus is served exclusively by the rostral posterior cerebral artery. The amygdala, the periamygdaloid cortex, and the piriform cortex are served by the middle cerebral artery and in part by the perforating arteries. The entorhinal, perirhinal, and postrhinal cortices are vascularized by the posterior and middle cerebral arteries, with a very broad overlap between the distal territories of these vessels. The demonstration of an extensive superimposition between the arterial supply of the entorhinal and the perirhinal regions suggests the presence of anastomotic connections that potentially are protective against ischemic events. Such an arrangement was not observed for the arteries that supply the ventral portion of the hippocampal formation and the basolateral amygdala, which showed nonoverlapping boundaries. The pathophysiological consequences of a similar vascular organization are discusse
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
Functional and structural correlates of magnetic resonance patterns in a new in vitro model of cerebral ischemia by transient occlusion of the medial cerebral artery.
No full textkoamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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