1,721,027 research outputs found
Volume-conducted epileptiform events between adjacent necortical slices in an interface tissue chamber
No full textFar-field" artifacts are presumed to contribute negligibly to the field potential activity recorded from brain slices maintained in vitro. While performing paired intracellular and field potential recordings from rat neocortical slices superfused with medium containing 4-aminopyridine + GABA receptor antagonists, we identified: (i) epileptiform discharges characterized by concomitant field oscillations (amplitude = 2.6-6.4 mV) and intracellular depolarizations as well as (ii) smaller amplitude (0.3-1.3 mV) field epileptiform events that were not associated with any intracellular activity. By placing an additional extracellular recording electrode into adjacent slices, we discovered that large amplitude, epileptiform discharges were generated concomitant to those seen in the first slice at the field potential level only. In addition, We found in these slices small amplitude, field discharges that were synchronous with those recorded intracellularly in the original slice. Analysis of the changes in field potential amplitude over space demonstrated that this parameter was reduced by approximately 60% when the recording electrode was moved from the slice generating the epileptiform activity to the bathing medium and further decreased in a quasi-linear mode when recordings were obtained from an adjacent slice. fit conclusion, these observations indicate that brain slices can, under appropriate conditions. produce field potentials that are of amplitude sufficient for being recorded from other slices in the tissue chamber. These findings suggest that caution should be taken in assuming that field potential activity seen in an in vitro brain slice is generated within the recorded tissue. (c) 2005 Elsevier B.V. All rights reserved
The H current blocker ZD7288 decreases epileptiform hyperexcitability in the rat neocortex by depressing synaptic transmission
No full textNeurons respond to intracellular injection of hyperpolarizing current pulses by generating depolarizing sags contributed by a cation current termed I-h. I-h modulates neuron excitability and rhythmicity. It is, however, unclear whether the net effect of changing Ih leads to facilitation or depression of cortical epileptiform activity. Here, we addressed this issue by using field and intracellular recordings to study the effects of ZD7288 (10-100 mu M), a bradycardic agent known to abolish I-h, on the epileptiform discharges (duration = 2.5 +/- 0.3 s, mean +/- SEM; interval of occurrence = 34.2 +/- 3.3 s, n = 30 slices) induced in rat neocortical slices by 4-aminopyridine and GABA receptor antagonists. ZD7288 abolished the depolarizing sags seen during injection of intracellular hyperpolarizing current pulses while increasing resting membrane potential and apparent input resistance. These effects, which were fully established with 10 mu M ZD7288, were associated with a dose-dependent decrease in the occurrence of spontaneous epileptiform events and a reduction in their duration (the latter change occurring at doses > 20 mu M). ZD7288 also caused a dose-dependent decrease of background postsynaptic potentials. Finally, ZD7288 could depress epileptiform activity during Cs+ pretreatment, a procedure known to block Ih. These data indicate that ZD7288 hampers neocortical epileptiform synchronization, but also suggest that most of this action reflects the ability of ZD7288 to decrease synaptic transmission. (c) 2006 Elsevier Ltd. All rights reserved
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
koamabayili/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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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