1,721,030 research outputs found
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
Neuroscience: Transforming Visual Percepts into Memories
No full textSummaryA new study shows that local field potential oscillations in the human entorhinal cortex and hippocampus are correlated with visual awareness
Decision Making: A Role for the Amygdala in Translating Goals into Choices
No full textA new fMRI study shows that the human amygdala is involved in goal-directed planning, further finding that amygdala activation during planning is predictive of someone’s willingness to forgo immediate small rewards in favor of delayed larger rewards
Learning and Representation of Declarative Memories by Single Neurons in the Human Brain
Full text linkEpisodic memories allow us to remember not only that we have seen an item before but also where and when we have seen it (context). Neurons in the medial temporal lobe (MTL) are critically involved in the acquisition of such memories. Since events happen only once, the ability to distinguish novel from familiar stimuli is crucial in order to rapidly encode such events after a single exposure. Theoretically, this is a hard learning problem (single-trial learning). Yet, successful detection of novelty is necessary for many types of learning. During retrieval, we can sometimes confidently report that we have seen something (familiarity) but cannot recollect where or when it was seen. Thus episodic memories have several components which can be recalled selectively. We recorded single neurons and local field potentials in the human hippocampus, amygdala, and anterior cingulate cortex while subjects remembered, and later retrieved, the identity and location of pictures shown. We describe two classes of neurons that exhibit such single-trial learning: novelty and familiarity detectors, which show a selective increase in firing for new and old stimuli, respectively. The neurons retain memory for the stimulus for at least 24 h. During retrieval, these neurons distinguish stimuli that will be successfully recollected from stimuli that will not be recollected. Similarly, they distinguish between failed and successful recognition. Pictures which were forgotten by the patient still evoked a non-zero response. Thus, their response can be different from the decision of the patient. Also, we demonstrate that listening to these neurons (during retrieval) enables a simple decoder to outperform the patient (i.e., it forgets fewer pictures). These data support a continuous strength of memory model of MTL function: the stronger the neuronal response, the better the memory (as opposed to a dual-process model). I also describe specific power increases in specific frequencies of the local field potential that are predictive of later retrieval success. These neural signatures, recorded during learning, thus indicate whether plasticity was successful or not
Testing Models of Human Declarative Memory at the Single-Neuron Level
No full textDeciphering the mechanisms of declarative memory is a major goal of neuroscience. While much theoretical progress has been made, it has proven difficult to experimentally verify key predictions of some foundational models of memory. Recently, single-neuron recordings in human patients have started to provide direct experimental verification of some theories, including mnemonic evidence accumulation, balance-of-evidence for confidence judgments, sparse coding, contextual reinstatement, and the ventral tegmental area (VTA)–hippocampus loop model. Here, we summarize the cell types that have been described in the medial temporal lobe and posterior parietal cortex, discuss their properties, and reflect on how these findings inform theoretical work. This body of work exemplifies the scientific power of a synergistic combination of modeling and human single-neuron recordings to advance cognitive neuroscience
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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