1,720,984 research outputs found
Cognitive Pathology in Parkinson's Disease: a cholinergic perspective
Get PDFCognitive impairment is a common non-motor symptom with a debilitating effect on functional capacity and quality of life in people with Parkinson's disease (PD). Mild cognitive impairment in PD already manifests in newly diagnosed patients and approximately 80% of PD patients eventually develop PD dementia over the course of the disease. The underlying pathology of cognitive impairment in PD is complex and includes the degeneration of multiple neurotransmitter systems, of which the cholinergic system is of particular importance. However, detailed assessment of the regional cortical and subcortical role of the cholinergic system in cognitive impairment across stages of PD is lacking. This dissertation broadens the knowledge on the cognitive pathology in PD from a cholinergic perspective, by providing new insights on the in vivo assessment of cholinergic imaging, and evaluating the relationship between cholinergic system and cognitive functioning in the early and more advanced stages of the disease. We demonstrated that [18F]FEOBV PET imaging allows for reliable and detailed assessment of the cholinergic system. In addition, we found early involvement of the cholinergic system in PD, demonstrating both cholinergic denervation as well as increased cholinergic binding in newly diagnosed PD patients. The latter might indicate a cholinergic compensation mechanism related to cognitive functioning in PD. Furthermore we demonstrated the regional cholinergic vulnerability related to cognitive domain functioning in more advanced PD, showing involvement of overlapping cholinergic regions. These findings provide new directions for clinical practice and future studies on the cholinergic pathology of cognitive impairment in PD
Cholinergic centro-cingulate network in Parkinson disease and normal aging
Get PDFDecreased cholinergic binding within the recently identified centro-cingulate brain network robustly has been shown to robustly correlate with the severity of cognitive impairment in Parkinson disease (PD). This network with key hubs within the cingulum, operculum and peri-central cortical regions also correlates with elements of parkinsonian motor impairments, including postural instability and gait difficulties, such as falls or freezing. MRI neuroimaging studies have shown that the anterior midcingulate cortex is a key node for cognitive aspects of movement generation, i.e., intentional motor control. Recent evidence also suggests a novel aspect of organization of primary motor cortex, describing “effector” regions for fine movement control intercalated with interlinked “inter-effector” regions devoted to whole-body control. A distinguishing feature of inter-effector regions is tight linkage to the cingular and opercular regions. Such inter-effector regions have been proposed to be part of a greater somato-cognitive action network necessary for integration of goals and movement. Recent evidence also points to vulnerabilities of cholinergic nerve terminals in the centro-cingulate network in older non-PD adults. These features of normal aging underscore that cortical cholinergic terminal losses in age-associated neurodegenerative disorders are likely not exclusively the result of disease-specific etiologies but also related to otherwise normal aging. Practical implications of this overlap are that addressing disease-specific and general aging etiologies involved in neurodegeneration, may be of benefit in age-associated neurodegenerative disorders where significant cholinergic systems degeneration is present.</p
Differentiation of Mouse Embryonic Stem Cells into Spiral Ganglion Neurons: A Therapeutic Approach to Deafness
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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
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