1,720,961 research outputs found
Combining energy and Laplacian regularization to accurately retrieve the depth of brain activity of diffuse optical tomographic data
No full textDiffuse optical tomography (DOT) provides data about brain function using surface recordings.
Despite recent advancements, an unbiased method for estimating the depth of absorption changes and for providing
an accurate three-dimensional (3-D) reconstruction remains elusive. DOT involves solving an ill-posed
inverse problem, requiring additional criteria for finding unique solutions. The most commonly used criterion is
energy minimization (energy constraint). However, as measurements are taken from only one side of the
medium (the scalp) and sensitivity is greater at shallow depths, the energy constraint leads to solutions that
tend to be small and superficial. To correct for this bias, we combine the energy constraint with another criterion,
minimization of spatial derivatives (Laplacian constraint, also used in low resolution electromagnetic tomography,
LORETA). Used in isolation, the Laplacian constraint leads to solutions that tend to be large and deep.
Using simulated, phantom, and actual brain activation data, we show that combining these two criteria results
in accurate (error <2 mm) absorption depth estimates, while maintaining a two-point spatial resolution of
<24 mm up to a depth of 30 mm. This indicates that accurate 3-D reconstruction of brain activity up to
30 mm from the scalp can be obtained with DOT
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
Pulsed out of awareness: EEG alpha oscillations represent a pulsed inhibition of ongoing cortical processing
No full textAlpha oscillations are ubiquitous in the brain, but their role in cortical processing remains a matter of debate. Recently, evidence has begun to accumulate in support of a role for Alpha oscillations in attention selection and control. In this thesis, a series of studies is presented investigating the role of Alpha oscillations in visual processing, learning, and awareness. I propose that Alpha oscillations represent a general pulsed inhibition in the brain.
Chapter 1 contains a review of evidence that 8-12 Hz oscillations in the brain have a general inhibitory role in cognitive processing, with an emphasis on their role in visual processing. Chapter 2 presents additional evidence for this general inhibitory role, in a study where EEG Alpha is used to predict the rate of improvement in a complex video game training program. Chapter 3 summarizes research supporting the proposal that Alpha represents a pulsed inhibition of ongoing neural activity. The phase of the ongoing EEG can influence evoked activity and subsequent processing. It is proposed that Alpha exerts its inhibitory role through alternating microstates of inhibition and excitation. Chapter 4 and Chapter 5 discuss evidence that this pulsed inhibition can be entrained to rhythmic stimuli in the environment, such that preferential processing occurs for stimuli at predictable moments, leading to oscillations in visual awareness. The entrainment of a preferential phase of ongoing Alpha oscillations may provide a mechanism for temporal attention in the brain. Chapter 6 reports the results of an experiment combining fast optical imaging using the event-related optical signal (EROS) with EEG recording in a meta-contrast masking task. This multimodal combination is used to investigate the network of brain areas oscillating at Alpha frequencies and their influence on visual awareness, as well as the frontal and parietal areas modulating this oscillatory activity.
Chapter 7 concludes that together, this series of studies provides the foundation for an account of Alpha oscillations as a general pulsed inhibition mechanism which can be entrained by external stimulation and modulated by top down influences from the fronto-parietal attention network. Given the rhythmic nature of this proposed inhibitory mechanism, this pulsed inhibitory account of Alpha has important implications for many common cognitive phenomena, such as the attentional blink, and seems to indicate that our visual experience may at least some times be coming through in waves.
Chapter 1 contains a review of evidence that 8-12 Hz oscillations in the brain have a general inhibitory role in cognitive processing, with an emphasis on their role in visual processing. Chapter 2 presents additional evidence for this general inhibitory role, in a study where EEG Alpha is used to predict the rate of improvement in a complex video game training program. Chapter 3 summarizes research supporting the proposal that Alpha represents a pulsed inhibition of ongoing neural activity. The phase of the ongoing EEG can influence evoked activity and subsequent processing, and it is proposed that Alpha exerts its inhibitory role through alternating microstates of inhibition and excitation. Chapter 4 and Chapter 5 discuss evidence that this pulsed inhibition can be entrained to rhythmic stimuli in the environment, such that preferential processing occurs for stimuli at predictable moments, leading to oscillations in visual awareness. The entrainment of preferential phase of ongoing Alpha oscillations may provide a mechanism for temporal attention in the brain. Chapter 6 reports the results of an experiment combining fast optical imaging using the event-related optical signal (EROS) with EEG recording in a meta-contrast masking task. This multimodal combination is used to investigate the network of brain areas oscillating at Alpha frequencies and their influence on visual awareness, as well as the frontal and parietal areas modulating this oscillatory activity.
Chapter 7 concludes that together, this series of studies provides the foundation for an account of Alpha oscillations as a general pulsed inhibition mechanism which can be entrained by external stimulation and modulated by top down influences from the fronto-parietal attention network. Given the rhythmic nature of this proposed inhibitory mechanism, this pulsed inhibitory account of Alpha has important implications for many common cognitive phenomena, such as the attentional blink, and seems to indicate that our visual experience may at least some times be coming through in waves.Item withdrawn by Mark Zulauf ([email protected]) on 2011-07-07T15:23:05Z
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Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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