1,720,982 research outputs found
Spatial attention asymmetries: behavioral and neural evidence
Full text linkHealthy individuals show a leftward attentional bias in the orienting of spatial attention, a phenomenon known as pseudoneglect. Spatial asymmetries have been demonstrated also in different planes (vertical and radial) and in the absence of any visual input (representational pseudoneglect). However, the relationship between spatial asymmetries across orientations and the underlying mechanisms of representational biases are still unclear and require further investigations.
Study 1 describes a psychophysical investigation on the effect of cognitive load on horizontal and vertical spatial asymmetries. Indeed, increasing cognitive load by introducing a secondary task, reduces the leftward bias in the horizontal plane. We investigated whether cognitive load has a similar effect on horizontal and vertical attentional asymmetries. Healthy participants were asked to carry out a line bisection and a landmark task in single and dual-task (while concurrently performing an auditory working memory task) conditions, in both horizontal and vertical orientations. We demonstrated that increasing cognitive load reduced the typical leftward/upward bias in the line bisection task, whereas it increased attentional biases in the landmark task. Interestingly, no differences were found between horizontal and vertical orientations, thus suggesting these biases may result from a common mechanism. However, the disparate effect of load across tasks suggests that these paradigms may engage different mechanisms.
In Study 2, we examined the role of a normal binocular vision in visual and haptic pseudoneglect. Indeed, strabismic amblyopes do not exhibit pseudoneglect in visual line bisection, suggesting that the right-hemisphere dominance in the control of spatial attention may depend on a normal binocular vision. We aimed to investigate whether an abnormal binocular experience also affects spatial attention in the haptic modality. Hence, we compared normally sighted, strabismic and early monocular blind participants in a visual and a haptic line bisection task. In visual line bisection, strabismic individuals tended to err to the right of the veridical centre, in contrast with normally sighted participants who showed pseudoneglect. Monocular blind participants exhibited high variability in their visual performance, with a tendency to bisect toward the direction of the functioning eye. In haptic bisection, all participants consistently erred towards the left of the veridical centre. Our findings support the view that pseudoneglect in the visual and haptic modality relies on different functional and neural mechanisms.
In Study 3, we explored the neural correlates of both perceptual and representational spatial asymmetries. Indeed, prior studies suggested a possible role of cerebellar regions in mediating spatial attention mechanisms; however, the extent and significance of the cerebellar contribution are not clear. Here, we aimed to shed light on this issue by means of two TMS experiments. In Experiment 3a participants completed a landmark task in two orientations (horizontal and vertical) while receiving single-pulse TMS over the cerebellar vermis, the visual cortex and the vertex (control sites). TMS over the vermis did not modulate participants' bias or response times, whereas TMS over the visual cortex delayed response latencies. In Experiment 3b, participants completed a landmark task and a number bisection task while TMS was delivered over the cerebellar vermis, the left cerebellar hemisphere and the vertex. TMS over the left cerebellar hemisphere delayed participants' response latencies in the number bisection task. Our data suggest that the left cerebellar hemisphere (but not the vermis) is causally implied in spatial attentional mechanisms in numeric intervals, but not physical lines, bisection.
Finally, the last chapter of the dissertation discusses and integrates the main findings of the studies illustrated in the experimental chapters.Healthy individuals show a leftward attentional bias in the orienting of spatial attention, a phenomenon known as pseudoneglect. Spatial asymmetries have been demonstrated also in different planes (vertical and radial) and in the absence of any visual input (representational pseudoneglect). However, the relationship between spatial asymmetries across orientations and the underlying mechanisms of representational biases are still unclear and require further investigations.
Study 1 describes a psychophysical investigation on the effect of cognitive load on horizontal and vertical spatial asymmetries. Indeed, increasing cognitive load by introducing a secondary task, reduces the leftward bias in the horizontal plane. We investigated whether cognitive load has a similar effect on horizontal and vertical attentional asymmetries. Healthy participants were asked to carry out a line bisection and a landmark task in single and dual-task (while concurrently performing an auditory working memory task) conditions, in both horizontal and vertical orientations. We demonstrated that increasing cognitive load reduced the typical leftward/upward bias in the line bisection task, whereas it increased attentional biases in the landmark task. Interestingly, no differences were found between horizontal and vertical orientations, thus suggesting these biases may result from a common mechanism. However, the disparate effect of load across tasks suggests that these paradigms may engage different mechanisms.
In Study 2, we examined the role of a normal binocular vision in visual and haptic pseudoneglect. Indeed, strabismic amblyopes do not exhibit pseudoneglect in visual line bisection, suggesting that the right-hemisphere dominance in the control of spatial attention may depend on a normal binocular vision. We aimed to investigate whether an abnormal binocular experience also affects spatial attention in the haptic modality. Hence, we compared normally sighted, strabismic and early monocular blind participants in a visual and a haptic line bisection task. In visual line bisection, strabismic individuals tended to err to the right of the veridical centre, in contrast with normally sighted participants who showed pseudoneglect. Monocular blind participants exhibited high variability in their visual performance, with a tendency to bisect toward the direction of the functioning eye. In haptic bisection, all participants consistently erred towards the left of the veridical centre. Our findings support the view that pseudoneglect in the visual and haptic modality relies on different functional and neural mechanisms.
In Study 3, we explored the neural correlates of both perceptual and representational spatial asymmetries. Indeed, prior studies suggested a possible role of cerebellar regions in mediating spatial attention mechanisms; however, the extent and significance of the cerebellar contribution are not clear. Here, we aimed to shed light on this issue by means of two TMS experiments. In Experiment 3a participants completed a landmark task in two orientations (horizontal and vertical) while receiving single-pulse TMS over the cerebellar vermis, the visual cortex and the vertex (control sites). TMS over the vermis did not modulate participants' bias or response times, whereas TMS over the visual cortex delayed response latencies. In Experiment 3b, participants completed a landmark task and a number bisection task while TMS was delivered over the cerebellar vermis, the left cerebellar hemisphere and the vertex. TMS over the left cerebellar hemisphere delayed participants' response latencies in the number bisection task. Our data suggest that the left cerebellar hemisphere (but not the vermis) is causally implied in spatial attentional mechanisms in numeric intervals, but not physical lines, bisection.
Finally, the last chapter of the dissertation discusses and integrates the main findings of the studies illustrated in the experimental chapters
Cerebellar contribution to emotional body language perception: a TMS study
No full textConsistent evidence suggests that the cerebellum contributes to the processing of emotional facial expressions. However, it is not yet known whether the cerebellum is recruited when emotions are expressed by body postures or movements, or whether it is recruited differently for positive and negative emotions. In this study, we asked healthy participants to discriminate between body postures (with masked face) expressing emotions of opposite valence (happiness vs. anger, Experiment 1), or of the same valence (negative: anger vs. sadness; positive: happiness vs. surprise, Experiment 2). Whilst performing the task, participants received online TMS over a region of the posterior left cerebellum and over two control sites (early visual cortex and vertex). We found that TMS over the cerebellum affected participants' ability to discriminate emotional body postures, but only when one of the emotions was negatively valenced (i.e., anger). These findings suggest that the cerebellar region we stimulated is involved in processing the emotional content conveyed by body postures and gestures. Our findings complement prior evidence on the role of the cerebellum in emotional face processing and have important implications from a clinical perspective, where non-invasive cerebellar stimulation is a promising tool in the treatment of motor, cognitive and affective deficits
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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