1,721,051 research outputs found
The transfer of visual information across the corpus callosum: spatial and temporal properties
No full textThe role of gamma-aminobutyric acid mediated inhibition in the response properties of cat lateral geniculate nucleus neurones.
No full textWe studied the effect of local ionophoretic application of bicuculline on the response of cat lateral geniculate nucleus (laminae A) cells to stimulation by sinusoidal gratings and spots of light. Application of bicuculline produced an increase both of spontaneous and visually driven discharge of both X and Y cells. On stimulation by drifting sinusoidal gratings, the average discharge of both X and Y cells remained constant with increasing contrast under normal conditions. Application of bicuculline caused the average discharge to increase with contrast, indicating that the constancy of the average discharge was maintained by gamma-aminobutyric acid mediated inhibition. Under normal conditions, the amplitude of response modulation of both X and Y cells to sinusoidal grating stimulation increased monotonically with stimulus contrast. During bicuculline application, the slope of the contrast-response curve for X cells but not for Y cells increased, indicating that the inhibition which dampened the modulation of X cells (but not Y cells) was contrast dependent. Application of acetylcholine also increased the average discharge and the amplitude of modulation of the cell responses, but this increase did not depend on stimulus contrast. Under normal conditions, X but not Y cells showed an attenuation of response and an increase in contrast threshold to low spatial frequencies. This attenuation vanished during bicuculline application. The shape of Y-cell response curves was unaffected by bicuculline. Bicuculline had the same effect on the non-linear component of Y-cell response as on the linear component. Although bicuculline had a different effect on the response of X and Y cells to stimulation by gratings, it reduced the antagonistic surround of both X and Y cells to a similar extent (revealed by plotting the cell receptive fields with flashed spots of light)
Development of gamma-aminobutyric acid mediated inhibition of X cells of the cat lateral geniculate nucleus.
No full textWe studied the development of gamma-aminobutyric (GABA) mediated inhibitory processes of the lateral geniculate nucleus cells in kittens of various age groups, by measuring the effect of ionophoretic application of GABA and bicuculline on cell response to sinusoidal gratings. In young kittens (less than 30 days) we found very few Y cells only X cells and weakly responsive cells which fitted neither X nor Y classifications ('immature' cells). As with adult cells, GABA inhibits the visual response of young kitten cells. Simultaneous application of bicuculline restored responsiveness. The mean GABA current to silence cell response in young kittens was significantly higher than that obtained in adult cats. Application of bicuculline alone had little effect on young kitten X-cell responsiveness, either on the average discharge or on the amplitude of modulation to stimulation by sinusoidal gratings. For older kittens (40-45 days), bicuculline increased X-cell responsiveness, and the increase in responsiveness was dependent on stimulus contrast and spatial frequency. However, the increased responsiveness was less than that for adults. At 100 days the changes of slope of X-cell contrast-response curves during bicuculline application were similar to those observed for adult X cells. We conclude that, although GABA receptors may be present at 30 days, the GABA mediated inhibitory system does not begin to function until about 45 days and does not mature fully until about 100 days
Interocular transfer of the adaptation after effect in neurons of area 17 and 18 of split-chiasm cats
No full textThe transfer of visual information across the corpus callosum in cats, monkeys and human beings: spatial and temporal properties.
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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
Martialis Epigrammaton liber decimus: Strategies for a second edition
No full textAnalisi del decimo libro degli Epigrammi, con lo scopo di individuare le caratteristiche strutturali della seconda edizione curata dal poeta nel 98 d.C
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