1,720,972 research outputs found
Repetita iuvant: object-centered neglect with non-verbal visual stimuli induced by repetition.
No full textNeglect can be ego-centered or object-centered depending on the reference frames for "left" and "right", of either the body or an object. It has been suggested that object-centered neglect is not a general phenomenon but is limited to words because only they have a true canonical representation. Here, we examined whether object-centered neglect could be observed for non-verbal material by creating, after repeated exposure, a canonical representation of a nonsense figure. Fourteen neglect patients repeatedly bisected a series of asymmetrical nonsense drawings containing two different shapes at their right and left end-points (canonical trials). In the critical trials, which were the last three in the series, the position of the two shapes was mirror-reversed. Afterwards, neglect patients were asked to draw the stimulus, which provided a further measure of whether a canonical representation of the object has been built by the patients. All the patients made rightward errors with the canonical stimuli. With mirror-reversed stimuli, the bisection errors were reversed to the contralesional side in one patient, returned to zero in one patient and significantly decreased in three patients. In addition, 10 patients reliably drew the canonical stimulus at the end of the series of trials, providing an indication that they built up a canonical representation of the stimulus. The present data provide evidence that object-centered neglect is a phenomenon that is not limited to words. The nature of a stimulus, verbal or non-verbal, is not critical for observing object-centered neglect. What is critical is the way in which material is represented by the patients
The two sides of spatial representation in neglect patients: the same spatial distortion for different patterns of performance.
No full textPatients with neglect show disorders in horizontal space perception. It has been argued that these disorders may depend on a distortion of space that takes the form of a left–right relaxation of the representational medium that becomes progressively “relaxed” toward the contralesional space and progressively “compressed” toward the ipsilesional space (the space anisometry hypothesis). In the present paper we tested this hypothesis by using the Oppel–Kundt illusion that consists of the perception of a filled space as larger than an empty space of the same size. Two experiments were carried out with 14 brain-damaged patients with neglect, 9 brain-damaged patients without neglect and 12 healthy subjects. In the first experiment participants were requested to bisect and read words with different letter spacing simulating the way space is thought to be distorted in neglect. In the second experiment we asked the participants to physically and numerically bisect numerical intervals. The results of the two experiments are in line with the predictions of the space anisometry hypothesis. Specifically, with a background resembling the space distortion proposed by the space anisometry hypothesis, neglect signs are ameliorated in reading words and in numerically bisect numerical intervals, while they are worsened in bisecting words and physically bisect numerical intervals. These results support the idea that the abnormalities observed in typical neglect tests are due to a distorted internal representation of the outside world that takes the form of a mental continuum logarithmically distorted along the horizontal dimension
Rightward and leftward bisection biases in spatial neglect: two sides of the same coin?
No full textNeglect patients, when asked to bisect a horizontal line, typically show large rightward errors with long lines and a decreased error with medium length lines. With very short lines the bisection bias reverses from the right to left side of the line physical centre (the so-called crossover effect). It is commonly pointed out that such a leftward bias is difficult to explain by traditional theories of neglect. Several accounts propose two distinct mechanisms, one that works for short lines and one that works for long. In the present study we demonstrated that the crossover effect can be explained by means of a unitary mechanism that derives from the space anisometry hypothesis. This hypothesis postulates that in neglect patients representational space is progressively 'relaxed' contralesionally and progressively 'compressed' ipsilesionally. In a series of five experiments, we investigated the crossover effect in 26 right-brain damaged patients: 17 with neglect without hemianopia, 4 with neglect and hemianopia and 6 without neglect or hemianopia. Patients were to bisect or extend lines of objectively and subjectively different lengths. The modulation of subjective length was created by an Oppel-Kundt illusion that is thought to resemble the distortion of representational space that occurs with neglect. All groups, except for the patients with neglect and hemianopia, were prone to the illusion. The rightward bias was reduced when the illusion induced a perceptual distortion opposite to that thought to underlie neglect. Importantly, the strength of the illusion decreased with reducing the physical line length and reversed with very short lines. These results argue for a simple and unitary explanation of the crossover effect in spatial neglect within the framework of the space anisometry hypothesis
What kind of visual spatial attention is impaired in neglect?
No full textThe distribution of spatial attention across the horizontal meridian of the visual field, as assessed by a simple reaction time (RT) paradigm, is dramatically abnormal in neglect patients. In the contralesional hemifield, RT increases sharply from centre to periphery, while in the ipsilesional hemifield, it decreases paradoxically from centre to mid-periphery. In the present study, we firstly asked whether this abnormal distribution of spatial attention is still present when patients know in advance the location of the impending stimulus, and second whether and to which extent it may be influenced by the concomitant presence of hemianopia. In Experiment 1, the stimuli were presented either predictably (blocks of same-point presentations) or unpredictably (blocks of randomised presentations) to one of several contralesional and ipsilesional field locations. As was the case for control subjects, neglect patients showed an overall RT decrease with same-point presentations. However, their abnormal contralesional RT lengthening and ipsilesional speeding were still present. In Experiment 2, the trials were blocked to same-hemifield presentations. In the ipsilesional field condition, neglect patients with and without hemianopia showed the same distorted distribution of attention favouring mid-periphery over central field locations. Two conclusions can be drawn from these experiments: first, the bulk of the abnormal deployment of spatial attention in neglect patients is related to an impairment of exogenous attention which cannot be compensated for by a spared endogenous control. Second, hemianopia does not affect the paradoxical speeding up of RT typically found in the mid-periphery of the ipsilesional field of neglect patients
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
Dalla giurisdizione all'amministrazione? Temi e problemi del percorso di rettificazione anagrafica del sesso
No full textIl saggio analizza l'intero percorso legislativo e giurisprudenziale italiano che ha condotto al riconoscimento progressivo dei vari diritti delle persone transgender. Si analizzano le questioni ancora aperte e, al proposito, si confrontano sinteticamente alcune esperienze straniere
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
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