1,720,965 research outputs found
The neural substrate of spatial memory stabilization depends on the distribution of the training sessions
Full text linkDistributed training is known to lead to more robust memory formation as compared to training experiences with short intervals. Although this phenomenon, termed distributed practice effect, ubiquitous over a wide variety of tasks and organisms, has long been known by psychologists, its neurobiological underpinning is still poorly understood. Using the striatum as a model system here we tested the hypothesis that the ability of distributed training to optimize memory might depend upon the recruitment of different neural substrates compared to those engaged by massed training. First, by contrasting the medial and the lateral domains of the dorsal striatum after massed and distributed training we demonstrated that neuronal activity, as assessed using c-Fos expression, is differentially affected by the training protocol in the two striatal subregions. Next, by blocking the AMPA receptors before recall we provide evidence to support a selective role of the medial and the lateral striatum in the storage of information acquired respectively by massed and distributed training. Finally, we found that optogenetic stimulation of the dorsolateral striatum during massed training enables the formation of an enduring memory similarly to what is observed with distributed learning. Overall, these findings identify a possible mechanism for the distributed practice effect, a still poorly understood aspect of learning
The Long Run: Neuroprotective Effects of Physical Exercise on Adult Neurogenesis from Youth to Old Age
Full text linkThe rapid lengthening of life expectancy has raised the problem of providing social programs to counteract the age-related cognitive decline in a growing number of older people. Physical activity stands among the most promising interventions aimed at brain wellbeing, because of its effective neuroprotective action and low social cost. The purpose of this review is to describe the neuroprotective role exerted by physical activity in different life stages. In particular, we focus on adult neurogenesis, a process which has proved being highly responsive to physical exercise and may represent a major factor of brain health over the lifespan
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
Impaired spatio-temporal coordination of subventricular neurogenesis is restored by physical exercise
No full textA major aim of neural stem cells field is to harness endogenous neurogenesis to replace neurons damaged as a consequence of brain damage and neurodegeneration. Olfactory interneurons arise throughout life from neural stem cells residing in the subventricular zone (SVZ) of the lateral ventricle. Post mitotic neuroblast then migrate along the rostral migratory stream (RMS) to the olfactory bulb where undergone to fully maturation and functional integration in the olfactory circuitry. To ensure a continuous source of newly-generated adult interneurons, stem and progenitor cell proliferation, neuroblast migration, and terminal differentiation must be tightly coordinated. In this study we analyzed the effect of physical exercise in orchestrating the different steps of subventricular neurogenesis in a mouse lacking the antiproliferative gene Btg1 which displays an impaired subventricular neurogenesis. As previously demonstrated Btg1 loss-of-function mice exhibit a strong reduction of proliferation associated with a premature exit from the cell cycle and an anticipated migration toward the olfactory bulb where the neuroblast fail to fully differentiate and consequently to be specifically recruited in olfactory-dependent memory circuitry.
In the study we demonstrate that running fully reverses the profound reduction of proliferation within the SVZ of the lateral ventricle in the Btg1-deficient mice, mainly through a recruitment and expansion of the quiescent neural stem cells (NSCs) . Moreover, cell cycle analysis reveals that 12 days of running induces a shortening of the S-phase and consequently of the whole cell cycle length in both neural stem (GFAP+, type C) and progenitor (DCX+, type A) cells of Btg1 knockout mice, allowing the restoring of a proper coordination between the cell cycle exit and the initial phase of post-mitotic neuroblasts migration. These events result in a increased rate of terminal maturation and integration in the olfactory- dependent memory circuits. Finally, as previously stated by others, we does not detect any beneficial effect of running in the subventricular zone wild type mice . All together these in vivo data suggest that a) the quiescent state of neural stem cells lacking the cell cycle inhibitory control can be reactivated by running; b) the cell cycle kinetics in the adult SVZ plays a pivotal role not only for proliferation but also for the tight coordination of cell cycle exit, migration and terminal differentiation.
In vitro analysis demonstrates that running induces a great expansion of primary neurospheres isolated by Btg1 ko subvrenticular zone, supporting the in vivo observation about the increase of neural stem pool in this neurogenic niche. However the running-dependent hyperproliferation of the neural stem cells leads to a rapid depletion of the stem cell pool and /or to its ability to further expand in vitro. This fact suggest that the effect of running on the Btg1 knock out neural stem cell proliferation is not cell-autonomous but strictly dependent on niche environment. We can hypothesized that the presence of still unknown factors triggered by physical activity in the subventricular niche promotes and maintains in vivo the hyperproliferative state of neural stem cells in the Btg1 knockout mice
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