1,720,974 research outputs found
Spontaneous saccades in young awake monkey.
No full textThe aim of this study is to compare the static and dynamic characteristics of young monkey's saccades with adult monkey's. The experiments were carried out on one young monkey of 80-90 days of life and on three adult monkeys. The eye movements were detected by magnetic field technique, in the dark and in the light. A soft cup was used for painless fixation of young animal's head. The analysis of eye movements was done by a PDP 11/73. The results show that the spatio-temporal pattern of eye movements is prevalently vertical or slightly oblique in young monkey, contrary it is prevalently horizontal or slightly oblique in the adult: besides the amplitudes are smaller and the velocities are slower in the adult. From these preliminary results we may think that maturation modifies the static and dynamic characteristics of eye movements
The saccadic eye movements in infant monkey.
No full textPrevious studies showed that the static and dynamic characteristics of eye movements between cat and kitten are different. The aim of this research is to study the effects of maturation, if there are any effects, on spatio-temporal characteristics of eye movements in the monkey. The experiments were carried out on one infant monkey (aged 80-90 days) and three adult monkey (Macaca nemestrina). Eye movements were detected by means of a magnetic field technique, in the dark and in the light. For painless fixation of the head Evart's technique was employed in adult monkeys while in the infant monkey a soft cup fixed to a suitable chair was used. The behavioural state was monitored by EEG and EMG. Eye movements were analised off-line by a PDP 11/73. Preliminary results show that the spatio-temporal pattern is prevalently vertical or slightly oblique in the infant monkey; on the contrary it is prevalently horizontal or oblique in the adults. Furthermore, the amplitudes of the saccades are smaller and the peak velocities are slower in the infant than in the adults. We may then argue that maturative processes act on ocular motility
Glial reaction to volkensin-induced selective degeneration of central neurons
No full textVolkensin, a highly toxic protein retrogradely transported through axons, was used to target primary neuronal death in brainstem precerebellar relays after injection in the cerebellar cortex of rats. The reaction of astrocytes and microglia was studied with immunohistochemistry in the inferior olivary and pontine nuclei from 6 h to 14 days. Neurodegenerative features were evident since the first hours, especially in the pontine nuclei, and neuronal loss reached a plateau at 7 days in the inferior olive and at 10 days in the pons. Astrocytic activation, revealed by glial fibrillary acidic protein immunoreactivity, was concomitant with early signs of neuronal death and gradually increased. Microglia activation, revealed by OX-42 immunoreactivity, was evident at 2 days and became rapidly intense in precerebellar relays. At 1 week, marked ED-1 immunoreactivity also revealed phagocytic features of microglia, which persisted during the second week. In addition, major histocompatibility complex antigens (MHC) class I and II were induced in cells exhibiting microglial features. In the inferior olive, MHC I immunoreactivity was evident since 4 days and persisted at 14 days, whereas MHC II induction was intense at 7 days and subsided at 2 weeks. In the pontine nuclei high expression of both MHC antigens persisted instead at 14 days, probably reflecting the progression of neuronal death. Thus, targeted lethal injury of central neurons elicited prompt activation of both astrocytes and microglia; the marked microglia activation resulted in phagocytic features and immunophenotypic changes, with a temporal regulation that paralleled the evolution of neurodegenerative phenomena. Copyright © 2001 Elsevier Science Inc
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
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
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
Suicide retrograde transport of volkensin in cerebellar afferents: direct evidence, neuronal lesions and comparison with ricin
No full textVolkensin and ricin, either free or conjugated with colloidal gold, were injected into the cerebellar cortex of rats. The inferior olive and pontine nuclei were examined to verify the retrograde axonal transport of these two toxins, and the consequent neuronal damage. No evidence was obtained of a retrograde axonal transport of ricin in these pathways. Injection of gold-conjugated volkensin in the cerebellar cortex resulted in retrogradely labelled neurones in the inferior olive after 3 h, and in the pontine nuclei after 6 h. Degenerative changes were very severe in the retrogradely labelled neurones 48 h after the gold-conjugated volkensin injection. In the Nissl-stained material, neuronal degeneration started to be evident in the inferior olive 12 h, and in pontine nuclei 6 h, after volkensin injection. The neuronal degeneration in both the inferior olive and pons increased up to 4 days after the injection. These findings provide direct evidence of the retrograde axonal transport of volkensin in the cen tral nervous system, and the time course of the consequent degenerative changes in the afferents to the cerebellar cortex
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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