1,721,068 research outputs found
The dopamine hypothesis of drug addiction: Hypodopaminergic state
No full textDrug addiction is a brain disorder caused by the repetitive use of various chemicals which alter normal functioning of the central nervous system with consequent behavioral abnormalities. In the search to understand which neuro- transmitter systems play upon this behavioral pathology, dopamine has long been thought to play a prima donna role. However, its primary role is commonly and erroneously attributed to the increase in activity after acute administration of addicting drugs. On the contrary, the mesolimbic dopamine transmission ap- pears to be drastically reduced in its tonic activity when measured in animal models, which mimic the human condition of drug addiction, and in the avail- able human studies conducted in addicted subjects. This paper is a systematic review of the pertinent literature which strongly supports this concept. Various experimental approaches such as electrophysiological, biochemical, behavioral, biomolecular and even anatomical, show that dopamine neurons work insuY- ciently in the crucial phases of the entire drug addiction cycle such as withdrawal from chronic treatment. This hypodopaminergic state is viewed as one of the main causes that triggers drug-seeking and taking, even after prolonged drug-free periods, perpetuating the vicious cycle. In addition, albeit reduced in its activity, the system remains hyperresponsive to abused drugs conferring long-lasting vulnerability to the system. We propose that decreased dopamine function in addicted subjects results in a decreased interest to non drug-related stimuli and increased sensitivity to the drug of choice. Targeting the dopamine system with pharmacological agents, not necessarily classic receptor-oriented drugs, aimed at restoring dopamine transmission may reveal useful new avenues in the treatment of this socially debilitating brain pathology
XAFS study of the local structure around Er3+ ion in thin Er-doped HfO2 thin films for advanced nanoelectronic applications
No full textWe propose to perform XAFS measurements to determine the local structure of Er3+ atoms in ultra-thin Er-doped HfO2 films, which are currently investigated as high-dielectric constant (high-k) oxides for advanced nanoelectronic applications
Persistent and Reversible Morphine Withdrawal-Induced Morphological Changes in the Nucleus Accumbens
No full textMorphine withdrawal produces a hypofunction of mesen- cephalic dopamine (DA) neurons which impinge upon medium spiny neurons (MSN) of the forebrain. After chronic treatment rats were ei- ther spontaneously or pharmacologically withdrawn from chronic mor- phine: under these two distinct conditions we studied the effects of withdrawal on spine density of MSN of the core and shell of the nu- cleus accumbens (NAcc) at various times (1–3–7–14 days). MSN were stained with the Golgi–Cox procedure and analyzed by a confocal laser- scanning microscope. Our analysis shows that both spontaneous and naloxone-induced withdrawal produces a long-lasting but reversible re- duction in spines’ density in shell MSN, as compared with core MSN. This effect is selectively localized at the level of second-order dendritic trunks and persists up to 14 days when spine density was found within control (pretreatment) values. By contrast, spine density counts of NAcc MSN from rats chronically treated with morphine, did not reveal any change over time. Collectively, the results of the present article suggest that spontaneous and pharmacologically precipitated withdrawal, but not chronic morphine, persistently but reversibly reduce spines’ density under a condition of reduced mesolimbic DA transmission, and the re- duction of spines’ density in second-order dendritic trunks is selectively segregated in the MSN of the shell of the NAcc. Morphine withdrawal dramatically, lastingly, and reversibly reduces spine density, selectively in second-order dendritic trunks of NAcc shell MSN, thereby further impoverishing the already abated DA transmission. These results may be relevant in the most harmful consequences of drug addiction such as craving and loss of control over intake and are in line with recent views suggesting the hypodopaminergic state as a cardinal feature of drug dependence
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
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