1,720,958 research outputs found
Responses of macaque V1 neurons to fixational and voluntary eye movements correlate with receptive field properties
No full textNatural viewing in primates consists of abrupt saccades followed by slower movements. We recorded the activity of single V1 neurons in response to a stationary bar while monkeys performed a fixation task or made voluntary saccades of different sizes. The classical receptive fields (CRFs) were mapped with drifting and flashing bars while compensating for fixational eye movements. Voluntary saccades were elicited so that the CRF would cross the stimulus bar, land on it, or leave it. Three characteristic patterns were found in response to both fixational and voluntary eye movements: 1) “Saccade” cells discharged transiently whenever the CRF was swept across, onto, or off the stimulus, but were not activated during intersaccadic periods even when the CRF was constantly on the stimulus. They had transient responses to flashes and were tuned for relatively high velocity. 2) “Position/drift” cells did not respond to rapid crossings of the stimulus but fired continuously while the stimulus was within the CRF. They had sustained flash responses, preferred low velocity, and tended to be selective for sign of contrast. 3) “Mixed” cells fired bursts of activity following saccades but also continued to fire at a lower rate during intersaccadic intervals, if the CRF remained on the stimulus. Their properties were intermediate between “saccade” and “position/drift” cells. In many “mixed” and “saccade” cells, the response decreased or disappeared with increasing size of crossing saccades. It remains an open question what causes this effect: a high velocity cut-off, an active suppression, or both. Our results suggest that different V1 neurons selectively extract information about motion, change, position and visual detail. Both fixational and voluntary saccades modulated neuronal firing in the absence of a visual stimulus, but the modulation was slower and much weaker than the visual response. Thus an extraretinal input to V1 is effective, even for the smallest saccades
Eye position influences contrast responses in V1 of alert monkey
No full textDo our cells in V1 respond differently when we look in different places? To answer this question, we have studied neuronal responses to moving bars in V1 of an alert monkey while it maintained different directions of gaze. The monkey was trained to fixate on an LED attached to the stimulus screen while the screen was placed in three positions: straight ahead or 0 deg (0 position), approximately 10 deg to the right (10R) or or to the left (10L) in the horizontal plane (h) in a constant vertical position (v). Recorded mean +/− SE eye positions in minarc were: for 0 position (h,v) = (2.5+/− 5.7, 5.3+/−3.8), for 10R position (516+/−16, −32+/−3), for 10L position (−540+/−12, 31+/−5). We have recorded contrast responses in 21 cells. Changing eye position significantly influenced the maximum amplitude of the response in 13 cells. In 4 cells where maximum responses were unchanged, responses to lower contrasts changed significantly for different eye positions. In 7/17 cells in 0 position, in 5/17 cells in 10R position and in 5/17 in 10L position, responses were larger than in other two positions. We have fitted contrast responses r(c) with the Naka-Rushton equation: r(c) = Rmax (c^n /(c^n + c50^n)), where Rmax is the maximum response, c — contrast, c50 -contrast at the half of Rmax, n — nonlinearity. We have analyzed only those responses with a sufficiently good fit (estimated by the RMS). In most cases changing the eye position had small influence on n, but significant influence on Rmax and c50. We have analyzed 18 contrast responses to increment and decrement bars. Rmax changed, more than 20%, in 12 cases and c50 in 14 cases. In 10 measurements both Rmax and c50 changed as the eye position changed. Our preliminary data also suggest that the eye position could differently influence the size of the increment and decrement zones in the classical receptive field of V1 cells
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
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
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
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