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a) Functional neuroanatomy as a function of the stimulation frequency; b) Somatotopic representations of individual fingers and lips
No full textTitelblatt, Zusammenfassung, Inhaltsverzeichnis, Abkuerzungsverzeichnis,
Danksagung und Eidesstattliche Erklaerung
Einleitung
Grundlagen
Material und Methoden
Ergebnisse
Diskussion
LiteraturverzeichnisAus invasiven tierexperimentellen Arbeiten und Untersuchungen des humanen
Kortex waehrend epilepsiechirurgischer Eingriffe durch Penfield und
Mitarbeiter ist seit den 1930ern bekannt, dass die Koerperoberflaeche
somatotop im primaeren somatosensorischen Kortex (SI) repraesentiert wird
(sog. Somatosensorischer Homunculus). Die vorliegende Arbeit sollte einen
Beitrag dazu liefern, Befunde zur Somatotopie nicht-invasiv zu erhalten, um
perspektivisch klinische Untersuchungen, z.B. zur zerebralen Plastizitaet zu
ermoeglichen. Es wurde die funktionelle Kernspintomographie (fMRT) eingesetzt,
um den primaeren somatosensorischen Kortex (SI) beim Menschen nicht-invasiv zu
untersuchen. Mittels elektrischer und nicht-schmerzhafter Stimulationen der
Finger und Lippen wurden die Aenderungen der lokalen Blutoxygenierung (BOLD-
Effekt) im primaeren somatosensorischen Kortex als Folge der neuronalen
Aktivitaet mit der fMRT gemessen und untersucht. In der ersten Studie wurde
die Frage untersucht, ob es einen Zusammenhang zwischen der elektrischen
Stimulationsfrequenz am Finger und dem fMRT-Signal in SI gibt. Es konnten
Aenderungen der Signalantwort kontralateral im Gyrus postcentralis in
Abhaengigkeit von der elektrischen Stimulationsfrequenz (1, 3, 7 und 10 Hz) am
rechten Zeigefinger gesehen werden. Die Steigerung der Stimulationsfrequenz
von 1 Hz auf 3 Hz und 7 Hz fuehrte zu einer Zunahme des aktivierten Volumens
und der Signalintensitaet. Wurde jedoch mit 10 Hz stimuliert, so kam es zu
keiner weiteren signifikanten Zu- oder Abnahme der gemessenen Parameter im
Vergleich zu 7 Hz. Diese Ergebnisse stimmten mit den Beobachtungen anderer
Arbeitsgruppen ueberein, die weitere Methoden (SEP, PET, NIRS) angewandt und
teilweise andere Spezies untersucht haben. Es laesst sich aus diesen
uebereinstimmenden Befunden folgern, dass es ab einer Stimulationsfrequenz von
7 Hz entweder zu keiner weiteren Zunahme der integrierten neuronalen
Aktivitaet oder zu einem Saettigungseffekt des BOLD-Signals in SI kommt. Aus
diesen Ergebnissen folgt hinsichtlich der Methodik weiterer fMRT-Studien, die
den primaeren somatosensorischen Kortex untersuchen, dass eine
Stimulationsfrequenz von 7 Hz am effektivsten erscheint, da es zur groessten
Signalzunahme in SI kommt. Im 2. und 3. Teil der Arbeit wurde die Frage
untersucht, ob die elektrisch stimulierten Finger 2 und 5 sowie Daumen, Unter-
und Oberlippe umschriebenen kortikalen Repraesentationsarealen in SI
zugeordnet werden kuennen und wie diese zueinander angeordnet sind. Es konnte
tatsaechlich mit der fMRT eine somatotope Anordnung der Repraesentationsareale
der Finger 2 und 5 sowie von Daumen, Unter- und Oberlippe kontralateral in SI
gezeigt werden. Die Repraesentation des zweiten Fingers war laterokaudal von
der des fuenften Fingers angeordnet. Die Repraesentationsareale von Daumen,
Ober- und Unterlippe konnten ebenfalls in einer somatotopen Abfolge von
mediokranial nach laterokaudal entlang des Sulcus centralis dargestellt
werden. In beiden Studien gab es jedoch bemerkenswerterweise jeweils einen
Probanden mit einer umgekehrten somatotopen Abfolge der
Repraesentationsareale, die als Normvariante interpretiert wurde. Die
angrenzenden Repraesentationsareale waren teilweise nicht getrennt voneinander
darstellbar sondern ueberlappten in vielen Faellen. Diese ueberlappende
Darstellung der Repraesentationsareale in SI koennte zum einen durch die
Methode bedingt sein, so waere es denkbar, dass die vaskulaere Reaktion auf
neuronale Aktivitaet eine eingeschraenkte raeumliche Aufloesung hat, somit die
ueberlappungen keine echten Phaenomene widerspiegeln. Ein anderer Grund
koennte darin liegen, dass in der (in der fMRT gemessenen) vaskulaeren Antwort
auch unterschwellige neuronale Aktivitaet sich widerspiegelt, welche bei
vielen der invasiven neurophysiologischen Untersuchungen nicht gemessen wurde.
Schliesslich ist aus tierexperimentellen, elektrophysiologischen
Untersuchungen bekannt, dass sich insbesondere in den Areae 1 und 2 die
rezeptiven Felder von benachbarten Fingern auch hinsichtlich ueberschwelliger
neuronaler Aktivitaet ueberschneiden koennen. Ein weiterer Befunde, der sich
in der Arbeit zeigte, war der Nachweis von mehreren voneinander
differenzierbaren Aktivierungen im kontralateralen primaeren
somatosensorischen Kortex. Diese liessen sich entweder der dorsalen Wand des
Sulcus centralis oder der Kuppe des Gyrus postcentralis zuordnen. Diese
multiplen Aktivierungen entsprechen deswegen vermutlich den
cytoarchitektonisch definierten Arealen 3b und 1/2. Aus tierexperimentellen
Untersuchungen ist jeweils eine eigene somatotope Repraesentation der
Koerperoberflaeche in den Arealen 3b und 1, zum Teil auch aus Area 2 und 3a
bekannt. Schliesslich konnten in der Arbeit neben Aktivierungen im
kontralateralen Gyrus postcentralis auch ipsilaterale Signalveraenderungen
nachgewiesen werden, ein Befund, der ebenfalls mit anderen bildgebenden
Untersuchungen am Menschen, wie auch mit tierexperimentellen Befunden
uebereinstimmt.Based on invasive experimental work in animals and interference studies of the
human cortex during surgical epilepsy performed by Penfield and coworkers it
is well-known since the 1930s that the body surface is represented
somatotopically in the primary somatosensory cortex. The aim of this thesis
work is to study somatotopy in humans using non-invasive methods. This should
provide the basis for future clinical studies about cerebral plasticity. The
primary somatosensory cortex (SI) was studied by the non-invasive method
functional MRI (fMRI).
Neuronal activity in response to non painful electrical stimulations of the
fingers and lips was measured by examining changes in the local BOLD response.
First we investigated if the fMRI signal in SI is a function of the electrical
stimulation frequency of the fingers. Responses that were observed
contralateral in the postcentral gyrus were a function of the electrical
stimulation frequencies at the right index finger (1Hz, 3Hz, 7Hz and 10Hz).
The volume of active area and the signal amplitude increased with the
stimulation frequency of up to 7Hz and remained constant at 10Hz. These
results are in agreement with previous studies in humans and other species,
that used other methods like SEP, PET and NIRS.
Based on these findings we conclude that a stimulation frequency of 7Hz leads
to maximal integrated neuronal activity in SI or to saturation of the BOLD
response. These data are useful for future fMRI studies of the somatosensory
cortex that require an optimal signal intensity.
Part 2 of this thesis work focused on the question whether the electrically
stimulated fingers 2 and 5 are represented in SI. It was of high interest to
map the relative distribution of these representation areas. In part 3 we
asked if the same principles apply as well for the representations of the
thumb and lower and upper lips.
Using fMRI we could show that fingers 2 and 5, as well as thumbs and lower and
upper lips are indeed represented somatotopically in SI. The representation of
the second finger was arranged laterocaudal to the representation of the fifth
finger. The representation areas of thumbs, upper and lower lip were detected
in a mediocranial to laterocaudal somatotopic succession along the central
sulcus. Remarkably, both studies each revealed one subject with a reversed
somatotopic succession of the described representation areas. We interpreted
these subjects as normal variants.
The observed adjacent representation areas overlapped in many cases. This
overlap could be due to a limited spatial resolution of the vascular reaction.
Another reason could lie in the fact that in (in the fMRI measured) vascular
the answer also lower neural activity reflects itself, which was not measured
with many of the invasive neurophysiological investigations.
Electricphysiological experiments in animals demonstrated that in area 1 and 2
the receptive fields of neighbouring fingers can indeed overlap in their
neural activity above threshold.
In this thesis work we further detected distinct activities in the
contralateral primary somatic sensory cortex. These activities could be
assigned either to the dorsal wall of the central sulcus or to the crest of
the postcentral gyrus. Therefore, these multiple activities probably
correspond to the cytoarchitectural defined areas 3b and 1/2. Experimental
animal studies revealed somatotopical representation of the body surface in
areas 3b, 1, 2 and 3a
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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