1,721,048 research outputs found
Effects of aging on interference control in selective attention and working memory
No full textWorking memory decay in advanced age has been attributed to a concurrent decrease in the ability to control interference. The present study contrasted a form of interference control in selective attention that acts upon the perception of external stimuli (access) with another form that operates on internal representations in working memory (deletion), in order to determine both of their effects on working memory efficiency in younger and older adults. Additionally, we compared memory performance under these access and deletion functions to performance in their respective control conditions. The results indicated that memory accuracy improved in both age groups from the access functions, but that only young adults benefited from the deletion functions. In addition, intrusion effects in the deletion condition were larger in older than in younger adults. The ability to control the irrelevant perception- and memory-elicited interference did not decline in general with advancing age; rather, the control mechanisms that operate on internal memory representations declined specifically
Effects of aging on visual contour integration and segmentation.
Full text linkPURPOSE:
Perception of circular disconnected contours requires the integration of relevant local orientation information across space and the suppression of irrelevant orientations. Using a detection of deviation from circularity (DFC) task, the present study examined whether the efficiency of either integrative or suppressive visual mechanisms, or both, declines with age.
METHODS:
Younger and older observers' sensitivities in detecting the DFC of a contour formed by Gabors were compared in three conditions: when all elements were oriented tangentially to the contour, with and without the presence of randomly oriented background noise; and when they had alternated tangential and orthogonal orientations, without background noise.
RESULTS:
In agreement with previous studies, the authors found that younger observers were not impaired in the mixed condition with respect to the tangential condition, suggesting the involvement of a high-level mechanism responding to the global closure information provided by tangential local orientations, even if they are interspersed with orthogonal ones. Instead, older observers were specifically impaired in the mixed condition, suggesting a reduced capability of suppressing nontangential information along the contour, and were also less efficient in suppressing irrelevant orientations in the background.
CONCLUSIONS:
These results support the suggestion that, whereas integrative mechanisms are not affected by age, suppressive mechanisms are
Neural Restoration Training improves visual functions and expands visual field of patients with homonymous visual field defects
No full textIn recent years, the introduction of visual rehabilitation for patients with homonymous visual field defects has been met with both enthusiasm and caution. Despite the evidence that restitutive training results in expansion of the visual field, several concerns have been raised
The Effects of Aging on Orientation Discrimination
Full text linkVisual perception relies on low-level encoding of local orientation. Recent studies show
an age-dependent impairment in orientation discrimination of stimuli embedded in
external noise, suggesting that encoding of orientation is inefficient in older adults. In
the present study we ask whether aging also reduces decoding, i.e., selecting the
neural representations of target orientation while discarding those conflicting with it.
We compared younger and older participants capability (mean age 24 and 68 years
respectively) in discriminating whether the orientation of a Gabor target was left or right
from the vertical. We measured (d0), an index of discrimination sensitivity, for orientation
offset ranging from 1 to 12. In the isolated target condition, d0 was reduced by
aging and, in the older group, did not increase with orientation offset, thus resulting
in a larger group difference at large than small orientation offsets from the vertical.
Moreover, oriented elements in the background impaired more discrimination in the
older group. However, distractors reduced more d0 when target-background orientation
offset was large than when target and flanker had similar orientation, indicating that
the effect of the background was not local, i.e., due to target inhibition by similarly
oriented flankers. Altogether, these results indicate that aging reduces the efficiency in
discarding the response to orientations differing from the target. Our results suggest
that neural decision-making mechanisms, involving not only signal enhancement but
also non-signal inhibition, become inefficient with age. This suggestion is consistent
with the neurophysiological evidence of inefficient visual cortical inhibition in aging
Perceptual learning improves contrast sensitivity, visual acuity, and foveal crowding in amblyopia
Full text linkBackground: Amblyopic observers present abnormal spatial interactions
between a low-contrast sinusoidal target and high-contrast collinear
flankers. It has been demonstrated that perceptual learning (PL) can
modulate these low-level lateral interactions, resulting in improved
visual acuity and contrast sensitivity.
Objective: We measured the extent and duration of generalization effects
to various spatial tasks (i.e., visual acuity, Vernier acuity, and
foveal crowding) through PL on the target's contrast detection.
Methods: Amblyopic observers were trained on a contrast-detection task
for a central target (i.e., a Gabor patch) flanked above and belowby two
high-contrast Gabor patches. The pre-and post-learning tasks included
lateral interactions at different target-to-flankers separations (i.e.,
2, 3, 4, 8 lambda) and included a range of spatial frequencies and
stimulus durations as well as visual acuity, Vernier acuity,
contrast-sensitivity function, and foveal crowding.
Results: The results showed that perceptual training reduced the
target's contrast-detection thresholds more for the longest
target-to-flanker separation (i.e., 8 lambda). We also found
generalization of PL to different stimuli and tasks: contrast
sensitivity for both trained and untrained spatial frequencies, visual
acuity for Sloan letters, and foveal crowding, and partially for Vernier
acuity. Follow-ups after 5-7 months showed not only complete maintenance
of PL effects on visual acuity and contrast sensitivity function but
also further improvement in these tasks.
Conclusion: These results suggest that PL improves facilitatory lateral
interactions in amblyopic observers, which usually extend over larger
separations than in typical foveal vision. The improvement in these
basic visual spatial operations leads to a more efficient capability of
performing spatial tasks involving high levels of visual processing,
possibly due to the refinement of bottom-up and top-down networks of
visual areas
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
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