1,720,968 research outputs found
Non-invasive structural and functional connectivity of the in-vivo human brain
Get PDFNeuroimaging enables us to image the human brain and reveal information about its structure and function. Diffusion imaging infers anatomical white matter trajectories. Resting state functional MRI indirectly measures neural activity by determining Blood Oxygenation Level Dependent (BOLD) signal response at rest, inferring functional connections between brain areas. These independent neuroimaging modalities are advantageous due to their non-invasive and in-vivo nature, providing insight into the human connectome. Their relationship is yet not understood. We explored the structural and functional connectivity of the human brain at a macroscopic level, and the extent to which anatomical connections constrain functional connections. We analysed the correlations between functional and structural connectomes and found a strong correlation beyond the mere effect of distance between brain regions (Chapter 6). Next we delved into two different types of brain organisations - topographic and nuclear. Topographic connections between cortical areas are often ignored in macro-connectome models. We investigated such arrangements by modelling and simulating gradient of connectivity patterns as an example to encourage and bring awareness of their properties for future involvement into studying brain connectivity (Chapter 7). Finally we studied nuclear brain organisations in the human amygdala. The amygdala can be clustered into two main subdivisions, basolateral and centromedial. The basolateral complex consists of the lateral, basal and accessory basal subnuclei, whereas the centromedial complex comprises of the central and medial subnuclei. We utilised the two independent imaging modalities to parcellate the amygdala into its respective subnuclei in a data-driven approach using the Human Connectome Project (HCP) data. We studied the distinct afferent/efferent cortical projections of the human amygdala, and we parcellated the amygdala into its five subnuclei, anatomically and into two subdivisions, functionally (Chapter 8). Studying the structural and functional connectivity in-vivo and non-invasively has provided evidence of their similarities, at the cortical and subcortical level
Relational representations for composition of knowledge and plans
Get PDFHumans have a remarkable capacity to understand and act in situations they have not encountered before. This capacity relies on clever representations of what is common across experience. Relational representations are particularly powerful for this purpose, because they allow for composing novel situations from familiar building blocks. In this thesis, I use neuroimaging and computational modelling to investigate how the brain constructs knowledge and plans.
In a functional magnetic resonance imaging experiment I study the origin of knowledge about objects and situations. Bar stools look like tables, but are conceptually more similar to sofas. What is the source of these abstract similarities? I hypothesise that the compositional regularities of experience induce meaning in objects and situations, reflected in brain activity along the temporal to the frontal lobe. To test this hypothesis, I designed a paradigm that probes neural representations from shape to understanding. In a controlled experiment with precise quantitative neural predictions, I do not find convincing evidence of the hypothesised abstract representations in the brain.
Through a computational model I propose a mechanism for constructing plans. When navigating a new city, we know that to visit a sight on the other side of the river, we have to find a bridge first. I show how building cognitive maps from relative positions of such common structural elements allows to immediately reuse previously learned plans. Object vector cells in entorhinal cortex are an attractive neural substrate to represent these relative positions, because they imply actions and path integrate. I propose a central role for replay in constructing the compositional map in hippocampus. The resulting model generalises plans, suppresses path integration noise, and extends naturally to hierarchical tasks.
This thesis thus suggests a central role for relational representations and composition in making sense of the world and making decisions in it
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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