1,721,016 research outputs found
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
Synaptic plasticity in neurodegenerative diseases evaluated and modulated by in vivo neurophysiological techniques
No full textSeveral studies demonstrated in experimental models and in humans synaptic plasticity impairment in some neurodegenerative and neuropsychiatric diseases such as Parkinson's disease, Alzheimer's disease, Huntington's disease, and schizophrenia. Recently new neurophysiological tools, such as repetitive transcranial magnetic stimulation and transcranial direct current stimulation, have been introduced in experimental and clinical settings for studying physiology of the brain and modulating cortical activity. These techniques use noninvasive transcranial electrical or magnetic stimulation to modulate neurons activity in the human brain. Cortical stimulation might enhance or inhibit the activity of cortico-subcortical networks, depending on stimulus frequency and intensity, current polarity, and other stimulation parameters such as the configuration of the induced electric field and stimulation protocols. On this basis, in the last two decades, these techniques have rapidly become valuable tools to investigate physiology of the human brain and have been applied to treat drug-resistant neurological and psychiatric diseases. Here we describe these techniques and discuss the mechanisms that may explain these effects
CONCOMITANT POST-TRAUMATIC CRANIOCERVICAL JUNCTION EPIDURAL HEMATOMA AND PONTOMEDULLARY JUNCTION INFARCTION: CLINICAL NEUROPHYSIOLOGIC, AND NEURORADIOLOGIC FEATURES.
No full textSTUDY DESIGN:
A case report.
OBJECTIVES:
To report and discuss a case of post-traumatic epidural hematoma of the craniocervical junction with concomitant brain stem infarction.
SUMMARY OF BACKGROUND DATA:
Post-traumatic epidural hematoma of the cervical spine and brain stem post-traumatic infarction are very rare disorders. Post-traumatic epidural hematoma is usually located dorsally in the epidural space.
METHODS:
The clinical, neuroradiologic, and neurophysiologic findings in one patient with post-traumatic epidural hematoma located ventrally at the cervicomedullary junction and associated with medial infarction at the pontomedullary junction are reported.
RESULTS:
The main clinical finding in this patient was bilateral corticospinal and corticobulbar tract involvement. A magnetic resonance image showed displacement and flattening of the medulla oblongata and of the most cranial portion of cervical cord, which were caused by the epidural hematoma associated with an ischemic lesion of the pontomedullary junction. Results of central motor conduction studies indicated that the abnormality of the central motor pathways was localized at brain stem level, and that there was normal conduction from the cervicomedullary junction to spinal cord.
CONCLUSION:
This is the first reported case of spinal epidural hematoma located ventrally in the cervical spine at the cervicomedullary junction level and concomitant infarction at the pontomedullary junction resulting from whiplash injury
Cerebral blood flow and metabolic changes produced by repetitive magnetic brain stimulation.
No full textJ Neurol. 1999 Dec;246(12):1164-8
Descending spinal cord volleys evoked by transcranial magnetic and electrical stimulation of the motor cortex leg area in conscious humans
No full text1. Descending corticospinal volleys evoked after transcranial magnetic or electrical stimulation of the leg area of the motor cortex were recorded from an electrode in the spinal epidural space of six conscious patients who had electrodes implanted for treatment of chronic pain, and from one anaesthetised patient undergoing surgery for a spinal tumour. 2. At threshold, the shortest-latency volley (L1 volley) was evoked by stimulation with an anode 2 cm lateral to the vertex. Anodal stimulation at the vertex also elicited a volley at this latency in two patients, but in the other patients the first volley evoked appeared 1-1.3 ms later (L2 volley), at the same latency as the initial volley evoked by magnetic stimulation. High-intensity stimulation of any type, could evoke both the L1 and L2 waves as well as later ones (L3, L4, etc.) that had a periodicity of about 1.5 ms. 3. Voluntary contraction increased the amplitude of the L2 and later volleys, but had no effect on the L1 volley. 4. Intracortical inhibition between pairs of magnetic stimuli resulted in clear suppression of the L4 and later waves. The L2 and L3 waves were unaffected. 5. In the anaesthetised patient the L1 volley occurred 1.7 ms later than the volley produced by transmastoid stimulation of the corticospinal pathways in the brainstem. 6. The L1 volley is likely to be a D wave produced by the direct activation of pyramidal axons in the subcortical white matter; the L2 and later volleys are likely to be I waves produced by the trans-synaptic activation of corticospinal neurones, The implication is that electrical stimulation with an anode at the vertex is more likely to evoke I waves preferentially than stimulation over the hand area. A more secure way to ensure D wave activation of corticospinal fibres from the leg area is to place the anode 2 cm lateral to the vertex
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
Cerebral Hemorrhage in a Paucisymptomatic Young Patient with Fabry Disease
No full textFabry disease is an inborn error of glycosphingolipid catabolism caused by deficient activity of the lysosomal exoglycohydrolase α-galactosidase A. It has an X-linked inheritance and occurs in all ethnic groups, with an incidence of 1 in 40,000 in the general population. The incidence of cerebrovascular accidents in patients affected by Fabry disease is much higher than in the general population. Moreover, there is a greater prevalence of hypertension, cardiac disease, and renal disease in patients affected by Fabry disease that have suffered a stroke. Here we present the case of a paucisymptomatic young man affected by Fabry disease and treated with enzyme replacement therapy who was admitted for hemorrhagic stroke
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
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