1,720,956 research outputs found
Covert orienting and focusing of attention in children withattention deficit hyperactivity disorder
Full text linkPerformance on the covert visuo-spatial attentional functions of orienting and focusing by a group of ADHD children (n = 20) was compared to that of age and sex-matched control children. In Experiment 1, responses were given to cued targets at valid and invalid locations. In Experiment 2, responses were given to targets presented in small, medium-sized or large visual field locations. For both experiments, the hypotheses that reaction times of ADHD children would be greater than those of control children and that performance would be asymmetrical, were supported. For Experiment 1, ADHD children showed bilaterally greater 'benefits' from having directed attention to the cued location and greater 'costs' in having to relocate the attentional focus than controls. In Experiment 2, the hypothesis that the function of focusing attention by ADHD children may show breakdown in the usual pattern of an increase in reaction time with focus area was partly supported by the finding of similar reaction times to targets presented in medium-sized and large regions of the left visual hemifield. These results have been interpreted as reflecting a stronger anchorage of attention by ADHD children upon a cued location and an inability to shift covert attention easily to an alternative location. The breakdown of the focusing function suggests adoption of similar time response sets across focus area size by the more compromised right hemisphere
Sudden and gradual presentation of distractor objects: differential interference effects
Full text linkIn solving the selection-for-action problem, it
is believed that attentional mechanisms enable dominance
of target over non-target objects. However, under
some conditions, information from non-target objects
“interferes” with the action to a relevant target. We investigated
the possibility that this interference may result
when the irrelevant object activates a specific subset of
visuomotor pathways. Participants reached to grasp
three-dimensional stimuli while actively attending to a
nearby flanker object. The means by which the flanker
was presented was manipulated. This relevant object was
illuminated either abruptly or gradually. The parvocellular
pathway in early visual processing is equally activated
in both conditions. The magnocellular pathway is
strongly activated by abrupt presentation and weakly activated
with gradual presentation of the flanker object.
Kinematics of the reach-to-grasp action to the target
showed signs of interference only in the sudden illumination
condition. This suggests a dissociation between
dorsal and ventral cortical streams in terms of relevance
for action. Our data suggests that this effect is not due to
early visual-pathway differences, but instead reveals a
property of a transient object-based visual attention
mechanism
The reach-to-grasp movement in Parkinson's disease before and after dopaminergic medication
No full textThe aim of the present study was to assess the effects of dopaminergic medication on the organisation of the reach-to-grasp
movement in Parkinson's disease. A three-dimensional kinematic system (ELITE, B|T|S| Italy) was used to record reach-to-grasp
movements to objects of either small (0.7 cm) or large (8 cm) diameter placed at a reaching distance of either 20 or 30 cm.
Vision of the reaching limb and target was also manipulated. Parkinson's disease participants (N =14) were assessed in `OFF'
(12 h without medication) and `ON' (1±2 h post-administration of medication) states. In the `ON' state, movement duration and
the time spent in arm deceleration were significantly less than in the `OFF' state. The amplitudes of peak reaching velocity,
acceleration and deceleration were all higher in the `ON' than in the `OFF' state. Further, in the `ON' state, the acceleration
profile no longer exhibited small irregular adjustments, the number of significant correlations between parameters measured
from the transport and manipulation components was greater, and the movement was more direct in both the mediolateral
horizontal and vertical planes. These results indicate that dopaminergic medication is of benefit in reducing bradykinesia and in
fine-tuning kinematic parameterisation of a selected reach-to-grasp action
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
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