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Neurophysiological mechanisms of quiet vigilance in neurodegenerative diseases: an electroencephalography research program
Get PDFIn the field of neurophysiological research, the term vigilance refers to a variety of mental states of monitoring of external world during wakefulness, related to activities in brain circuits (Steriade, 1999), projections of ascending reticular activating systems (ARASs) using dopaminergic, noradrenergic, serotonergic, histaminergic, cholinergic, and glutamatergic neurotransmitters (Moruzzi and Magoun, 1949). Malfunctioning of these neuromodulatory circuits may cause a variety of behavioural and cognitive dysfunctions as those observed in the most common progressive neurodegenerative dementing disorders such as Alzheimer’s (AD), Parkinson’s (PD), and Lewy Bodies diseases (DLB; Berridge et al., 2003; Gratwicke et al., 2015). AD, PD and DLB suffer of a progressive loss of cognitive functions. Typical clinical manifestation of AD is severe deficits in episodic memory while PD and DLB are both characterized by frontal executive deficits and motor symptoms (Alzheimer’s society 2017; McKeith et al., 2004). Compared with AD and PD patients, DLB patients have more frequent neuropsychiatric symptoms such as psychosis, depression, apathy and abnormalities in sleep behavior (Aarsland et al., 2005). However, there is limited information regarding the prodromal state of these type of dementia, and it need of a clinical markers to support decision-making processes underlying clinical management of AD, PD and DLB patients. The electroencephalography in resting-state condition (rsEEG) can be a valid candidate for this purpose as it can probe cortical arousal in quiet wakefulness, as revealed by the effects of the administration of a pharmacological agent enhancing vigilance (i.e., modafinil) and sleep deprivation on the regulation of brain rsEEG rhythms in humans (Del Percio et al., 2019). The aim of this PhD thesis was to improve our understanding of neurophysiological correlates of the quiet vigilance in patients with the most prevalent neurodegenerative dementing disorders such as AD, PD, and DLB. This aim was pursued by three retrospective rsEEG studies developed in the international clinical and EEG databases of High-resolution EEG Laboratory at the Department of Physiology and Pharmacology “V. Erspamer” at Sapienza University of Rome. These studies were developed in cooperation with the Partners of European Consortium of DLB. In the first study, we tested the hypothesis that resting state eyes-closed electroencephalographic (rsEEG) rhythms might reflect cortical arousal in patients with dementia due to AD (ADD), PD (PDD), and Lewy body disease (DLB). Clinical and rsEEG data of 42 ADD, 42 PDD, 34 DLB, and 40 healthy elderly (Nold) subjects were extracted from our international archive. Demography, education, and Mini Mental State Evaluation score were not different between the patient groups. Individual alpha frequency peak (IAF) determined the delta (< 4 Hz), theta (3-5 Hz), alpha1 (5-7 Hz), alpha2 (7-9 Hz), and alpha3 (9-13 Hz) frequency bands. Fixed beta1 (14-20 Hz), beta2 (20-30 Hz), and gamma (30-40 Hz) frequency bands were also considered. The rsEEG cortical sources were estimated by means of the exact low-resolution brain electromagnetic source tomography and were then classified across individuals, on the basis of the receiver operating characteristic curves. Results were quite interesting at both group and individual levels. At the group level, compared to the Nold subjects, IAF showed marked slowing in the PDD and DLB patients and moderate slowing in the ADD patients. Furthermore, all patient groups over the Nold subjects showed lower posterior alpha 2 source activities. This effect was dramatic in the ADD, marked in the DLB, and moderate in the PDD patients. These groups of patients also showed higher occipital delta source activities, but this effect was dramatic in the PDD, marked in the DLB, and moderate in the ADD patients. At the individual level, the posterior delta and alpha sources allowed good classification accuracy (approximately 0.85-0.90) between the Nold subjects and patients, and between ADD and PDD patients. We concluded that in quiet vigilance, delta and alpha sources unveiled different spatial and frequency features of the cortical neural synchronization underpinning brain arousal in ADD, PDD, and DLB patients. In the second study, we hypothesized that PD patients may show peculiar clinical manifestations related to vigilance (i.e., executive cognitive deficits and visual hallucinations), reflected in rsEEG rhythms. Clinical and rsEEG rhythms in age-, sex-, and education-matched PD (N = 93), AD (N= 70), and Nold (N = 60) subjects were available from the same international archive of the first study. The same methodology for EEG sources estimation was applied as well. Results showed that: (1) compared to the Nold subjects, the AD and PD patients showed higher widespread delta source activities (PD > AD) and lower posterior alpha source activities (AD > PD); (2) the PD patients with the most pronounced motor deficits exhibited very low alpha source activities in widespread cortical regions; (3) the PD patients with the strongest cognitive deficits showed higher delta and alpha source activities in widespread cortical regions; and (4) compared to the PD patients without visual hallucinations, those with visual hallucinations were characterized by higher parieto-occipital alpha sources activities. These results suggest that in PD patients resting in quiet vigilance, abnormalities in cortical neural synchronization at delta and alpha frequencies are differently related to cognitive, motor, and visual hallucinations. The third study tested if cortical sources of rsEEG rhythms may differ as a function of different clinical symptoms in sub-groups of patients with dementia with DLB. Clinical and rsEEG rhythms in age-, sex-, and education-were matched in DLB (N=46), AD (N=60), and Nold (N=20) subjects. Results showed that compared with the Nold subjects, the DLB and AD patients exhibited greater spatially distributed delta source activities (DLB > AD) and lower alpha source activities posteriorly (AD > DLB). In relation to the DLB controls, the DLB patients with (1) rapid eye movement (REM) sleep behavior disorders showed lower delta and alpha source activities in widespread posterior cortical regions; (2) greater cognitive deficits exhibited higher delta source activities posteriorly; (3) visual hallucinations pointed to greater parieto-frontal delta and parietal alpha source activities; (4) cognitive fluctuations manifested higher parietal alpha source activities. These rsEEG results suggest that when prominent, any clinical feature was associated with a different topography of delta and alpha source activities in the DLB patients. In conclusion, the three studies unveiled specific abnormalities in rsEEG rhythms at delta and alpha frequencies in AD, PD, and DLB patients experiencing quiet vigilance. These effects may represent the neurophysiological correlates of abnormalities in ARASs, cortical arousal, and cholinergic and dopaminergic systems probed by EEG techniques in AD, PD, and DLB patients. These effects were strictly related to clinical manifestations of the mentioned diseases. Future studies may cross-validate those results in prospective, harmonized rsEEG studies in AD, PD, and DLB patients followed from prodromal to dementia stages of the diseases
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
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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