473 research outputs found
Bistable Perception Is Biased by Search Items but Not by Search Priming
Publisher's version (útgefin grein)During visual search, selecting a target facilitates search for similar targets in the future, known as
search priming. During bistable perception, in turn, perceiving one interpretation facilitates
perception of the same interpretation in the future, a form of sensory memory. Previously, we
investigated the relation between these history effects by asking: can visual search influence
perception of a subsequent ambiguous display and can perception of an ambiguous display
influence subsequent visual search? We found no evidence for such influences, however. Here,
we investigated one potential factor that might have prevented such influences from arising: lack of
retinal overlap between the ambiguous stimulus and the search array items. In the present work,
we therefore interleaved presentations of an ambiguous stimulus with search trials in which the
target or distractor occupied the same retinal location as the ambiguous stimulus. Nevertheless,
we again found no evidence for influences of visual search on bistable perception, thus
demonstrating no close relation between search priming and sensory memory. We did,
however, find that visual search items primed perception of a subsequent ambiguous stimulus at
the same retinal location, regardless of whether they were a target or a distractor item: a form of
perceptual priming. Interestingly, the strengths of search priming and this perceptual priming were
correlated on a trial-to-trial basis, suggesting that a common underlying factor influences both.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or
publication of this article: M. A. B. B. is supported by the Icelandic Research Fund (Rannis, #130575-
051). A. K. is supported by the European Research Council (grant 643636), the Icelandic Research
Fund (#152427-051 & #173947-051), and the Research Fund at the University of IcelandPeer Reviewe
Temporal Characteristics of Priming of Attention Shifts Are Mirrored by BOLD Response Patterns in the Frontoparietal Attention Network
Publisher's version (útgefin grein)Priming of attention shifts involves the reduction in search RTs that occurs when target location or target features repeat. We used functional magnetic resonance imaging to investigate the neural basis of such attentional priming, specifically focusing on its temporal characteristics over trial sequences. We first replicated earlier findings by showing that repetition of target color and of target location from the immediately preceding trial both result in reduced blood oxygen level-dependent (BOLD) signals in a cortical network that encompasses occipital, parietal, and frontal cortices: lag-1 repetition suppression. While such lag-1 suppression can have a number of explanations, behaviorally, the influence of attentional priming extends further, with the influence of past search trials gradually decaying across multiple subsequent trials. Our results reveal that the same regions within the frontoparietal network that show lag-1 suppression, also show longer term BOLD reductions that diminish over the course of several trial presentations, keeping pace with the decaying behavioral influence of past target properties across trials. This distinct parallel between the across-Trial patterns of cortical BOLD and search RT reductions, provides strong evidence that these cortical areas play a key role in attentional priming.Icelandic Research Fund (Rannis, #130575-051 to M.B. and J.W.B.); the ERC (grant 643636 to A.K.); the Icelandic Research Fund (#130575-051, #152427-051 and #173947-051); and the Research Fund of the University of Iceland. Netherlands Organization for Scientific Research (grant #452.17.012 to B.M.) and Portuguese Foundation for Science and Technology (grant #IF/01405/2014 to B.M.).Peer Reviewe
Three-Charge Black Holes on a Circle
We study phases of five-dimensional three-charge black holes with a circle in
their transverse space. In particular, when the black hole is localized on the
circle we compute the corrections to the metric and corresponding
thermodynamics in the limit of small mass. When taking the near-extremal limit,
this gives the corrections to the constant entropy of the extremal three-charge
black hole as a function of the energy above extremality. For the partial
extremal limit with two charges sent to infinity and one finite we show that
the first correction to the entropy is in agreement with the microscopic
entropy by taking into account that the number of branes shift as a consequence
of the interactions across the transverse circle. Beyond these analytical
results, we also numerically obtain the entire phase of non- and near-extremal
three- and two-charge black holes localized on a circle. More generally, we
find in this paper a rich phase structure, including a new phase of
three-charge black holes that are non-uniformly distributed on the circle. All
these three-charge black hole phases are found via a map that relates them to
the phases of five-dimensional neutral Kaluza-Klein black holes.Comment: 58 pages, 10 figures; v2: Corrected typos, version appearing in JHE
Boundary Liouville theory at c=1
The c=1 Liouville theory has received some attention recently as the
Euclidean version of an exact rolling tachyon background. In an earlier paper
it was shown that the bulk theory can be identified with the interacting c=1
limit of unitary minimal models. Here we extend the analysis of the c=1-limit
to the boundary problem. Most importantly, we show that the FZZT branes of
Liouville theory give rise to a new 1-parameter family of boundary theories at
c=1. These models share many features with the boundary Sine-Gordon theory, in
particular they possess an open string spectrum with band-gaps of finite width.
We propose explicit formulas for the boundary 2-point function and for the
bulk-boundary operator product expansion in the c=1 boundary Liouville model.
As a by-product of our analysis we also provide a nice geometric interpretation
for ZZ branes and their relation with FZZT branes in the c=1 theory.Comment: 37 pages, 1 figure. Minor error corrected, slight change in result
(1.6
Instabilities of Black Strings and Branes
We review recent progress on the instabilities of black strings and branes
both for pure Einstein gravity as well as supergravity theories which are
relevant for string theory. We focus mainly on Gregory-Laflamme instabilities.
In the first part of the review we provide a detailed discussion of the
classical gravitational instability of the neutral uniform black string in
higher dimensional gravity. The uniform black string is part of a larger phase
diagram of Kaluza-Klein black holes which will be discussed thoroughly. This
phase diagram exhibits many interesting features including new phases,
non-uniqueness and horizon-topology changing transitions. In the second part,
we turn to charged black branes in supergravity and show how the
Gregory-Laflamme instability of the neutral black string implies via a
boost/U-duality map similar instabilities for non- and near-extremal smeared
branes in string theory. We also comment on instabilities of D-brane bound
states. The connection between classical and thermodynamic stability, known as
the correlated stability conjecture, is also reviewed and illustrated with
examples. Finally, we examine the holographic implications of the
Gregory-Laflamme instability for a number of non-gravitational theories
including Yang-Mills theories and Little String Theory.Comment: 119 pages, 16 figures. Invited review for Classical and Quantum
Gravit
Of Bounces, Branes and Bounds
Some recent studies have considered a Randall-Sundrum-like brane world
evolving in the background of an anti-de Sitter Reissner-Nordstrom black hole.
For this scenario, it has been shown that, when the bulk charge is
non-vanishing, a singularity-free ``bounce'' universe will always be obtained.
However, for the physically relevant case of a de Sitter brane world, we have
recently argued that, from a holographic (c-theorem) perspective, such brane
worlds may not be physically viable. In the current paper, we reconsider the
validity of such models by appealing to the so-called ``causal entropy bound''.
In this framework, a paradoxical outcome is obtained: these brane worlds are
indeed holographically viable, provided that the bulk charge is not too small.
We go on to argue that this new finding is likely the more reliable one.Comment: 15 pages, Revtex; references added and very minor change
Protocol: Health, social care and technological interventions to improve functional ability of older adults: Evidence and gap map
This is the final version. Available on open access from Wiley via the DOI in this frecordThis is a protocol for a Campbell Evidence and Gap Map. The objectives are to identify and assess the available evidence on health, social care and technological interventions to improve functional ability among older adults
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