1,926 research outputs found
Age of second language acquisition affects nonverbal conflict processing in children : an fMRI study
Background: In their daily communication, bilinguals switch between two languages, a process that involves the selection of a target language and minimization of interference from a nontarget language. Previous studies have uncovered the neural structure in bilinguals and the activation patterns associated with performing verbal conflict tasks. One question that remains, however is whether this extra verbal switching affects brain function during nonverbal conflict tasks.
Methods: In this study, we have used fMRI to investigate the impact of bilingualism in children performing two nonverbal tasks involving stimulus-stimulus and stimulus-response conflicts. Three groups of 8-11-year-old children - bilinguals from birth (2L1), second language learners (L2L), and a control group of monolinguals (1L1) - were scanned while performing a color Simon and a numerical Stroop task. Reaction times and accuracy were logged.
Results: Compared to monolingual controls, bilingual children showed higher behavioral congruency effect of these tasks, which is matched by the recruitment of brain regions that are generally used in general cognitive control, language processing or to solve language conflict situations in bilinguals (caudate nucleus, posterior cingulate gyrus, STG, precuneus). Further, the activation of these areas was found to be higher in 2L1 compared to L2L.
Conclusion: The coupling of longer reaction times to the recruitment of extra language-related brain areas supports the hypothesis that when dealing with language conflicts the specialization of bilinguals hampers the way they can process with nonverbal conflicts, at least at early stages in life
Measurements of Sunyaev-Zel'dovich Effect Scaling Relations for Clusters of Galaxies
We present new measurements of the Sunyaev-Zel'dovich (SZ) effect from
clusters of galaxies using the Sunyaev-Zel'dovich Infrared Experiment (SuZIE
II). We combine these new measurements with previous cluster observations with
the SuZIE instrument to form a sample of 15 clusters of galaxies. For this
sample we calculate the central Comptonization, y, and the integrated SZ flux
decrement, S, for each of our clusters. We find that the integrated SZ flux is
a more robust observable derived from our measurements than the central
Comptonization due to inadequacies in the spatial modelling of the
intra-cluster gas with a standard Beta model. This is highlighted by comparing
our central Comptonization results with values calculated from measurements
using the BIMA and OVRO interferometers. On average, the SuZIE calculated
central Comptonizations are approximately 60% higher in the cooling flow
clusters than the interferometric values, compared to only approximately 12%
higher in the non-cooling flow clusters. We believe this discrepancy to be in
large part due to the spatial modelling of the intra-cluster gas. From our
cluster sample we construct y-T and S-T scaling relations. The y-T scaling
relation is inconsistent with what we would expect for self-similar clusters;
however this result is questionable because of the large systematic uncertainty
in the central Comptonization. The S-T scaling relation has a slope and
redshift evolution consistent with what we expect for self-similar clusters
with a characteristic density that scales with the mean density of the
universe. We rule out zero redshift evolution of the S-T relation at 90%
confidence.Comment: Accepted to Astrophysical Journal. 52 pages, 14 tables, 7 figures
;replaced to match ApJ accepted versio
Age-related delay in visual and auditory evoked responses is mediated by white- and grey-matter differences
Slowing is a common feature of ageing, yet a direct relationship between neural slowing and brain atrophy is yet to be established in healthy humans. We combine magnetoencephalo-graphic (MEG) measures of neural processing speed with magnetic resonance imaging (MRI) measures of white and grey matter in a large population-derived cohort to investigate the relationship between age-related structural differences and visual evoked field (VEF) and auditory evoked field (AEF) delay across two different tasks. Here we use a novel technique to show that VEFs exhibit a constant delay, whereas AEFs exhibit delay that accumulates over time. White-matter (WM) microstructure in the optic radiation partially mediates visual delay, suggesting increased transmission time, whereas grey matter (GM) in auditory cortex partially mediates auditory delay, suggesting less efficient local processing. Our results demonstrate that age has dissociable effects on neural processing speed, and that these effects relate to different types of brain atrophy.Peer reviewe
Single-probe serial position recall: evidence of modularity for olfactory, visual and auditory short-term memory
The present study examined and compared order memory for a list of sequentially presented odours, unfamiliar-faces and pure-tone. Employing single-probe serial position recall and following a correction for a response bias, qualitatively different serial position functions were observed across stimuli. Participants demonstrated an ability to perform absolute order memory judgments for odours. Furthermore, odours produced an absence of serial position effects, unfamiliar-faces produced both primacy and recency and pure-tones produced recency but not primacy. Such a finding is contrary to the proposal by Ward, Avons and Melling (2005) that the serial position function is task, rather than modality, dependent. In contrast, the observed functions support a modular conceptualisation of short-term memory (e.g. Andrade and Donaldson, 2007; Baddeley and Hitch, 1974), whereby separate modality-specific memorial systems operate. An alternative amodal interpretation is also discussed wherein serial position function disparities are accommodated via differences in the psychological distinctiveness of stimuli (Hay, Smyth, Hitch and Horton, 2007)
A Bell Inequality Analog in Quantum Measure Theory
One obtains Bell's inequalities if one posits a hypothetical joint
probability distribution, or {\it measure}, whose marginals yield the
probabilities produced by the spin measurements in question. The existence of a
joint measure is in turn equivalent to a certain causality condition known as
``screening off''. We show that if one assumes, more generally, a joint {\it
quantal measure}, or ``decoherence functional'', one obtains instead an
analogous inequality weaker by a factor of . The proof of this
``Tsirel'son inequality'' is geometrical and rests on the possibility of
associating a Hilbert space to any strongly positive quantal measure. These
results lead both to a {\it question}: ``Does a joint measure follow from some
quantal analog of `screening off'?'', and to the {\it observation} that
non-contextual hidden variables are viable in histories-based quantum
mechanics, even if they are excluded classically.Comment: 38 pages, TeX. Several changes and added comments to bring out the
meaning more clearly. Minor rewording and extra acknowledgements, now closer
to published versio
Influence of Lorentz violation on Dirac quasinormal modes in the Schwarzschild black hole spacetime
Using the third-order WKB approximation and monodromy methods, we investigate
the influence of Lorentz violating coefficient (associated with a special
axial-vector field) on Dirac quasinormal modes in the Schwarzschild
black hole spacetime. At fundamental overtone, the real part decreases linearly
as the parameter increases. But the variation of the imaginary part with
becomes more complex. For the larger multiple moment , the magnitude of
imaginary part increases with the increase of , which means that presence of
Lorentz violation makes Dirac field damps more rapidly. At high overtones, it
is found that the real part of high-damped quasinormal frequency does not tend
to zero, which is quite a different from the symptotic Dirac quasinormal modes
without Lorentz violation.Comment: 10 pages, 4 figur
Causation, Measurement Relevance and No-conspiracy in EPR
In this paper I assess the adequacy of no-conspiracy conditions employed in
the usual derivations of the Bell inequality in the context of EPR
correlations. First, I look at the EPR correlations from a purely
phenomenological point of view and claim that common cause explanations of
these cannot be ruled out. I argue that an appropriate common cause explanation
requires that no-conspiracy conditions are re-interpreted as mere common
cause-measurement independence conditions. In the right circumstances then,
violations of measurement independence need not entail any kind of conspiracy
(nor backwards in time causation). To the contrary, if measurement operations
in the EPR context are taken to be causally relevant in a specific way to the
experiment outcomes, their explicit causal role provides the grounds for a
common cause explanation of the corresponding correlations.Comment: 20 pages, 1 figur
Parallel Unsmoothed Aggregation Algebraic Multigrid Algorithms on GPUs
We design and implement a parallel algebraic multigrid method for isotropic
graph Laplacian problems on multicore Graphical Processing Units (GPUs). The
proposed AMG method is based on the aggregation framework. The setup phase of
the algorithm uses a parallel maximal independent set algorithm in forming
aggregates and the resulting coarse level hierarchy is then used in a K-cycle
iteration solve phase with a -Jacobi smoother. Numerical tests of a
parallel implementation of the method for graphics processors are presented to
demonstrate its effectiveness.Comment: 18 pages, 3 figure
Quantum Histories and Quantum Gravity
This paper reviews the histories approach to quantum mechanics. This
discussion is then applied to theories of quantum gravity. It is argued that
some of the quantum histories must approximate (in a suitable sense) to
classical histories, if the correct classical regime is to be recovered. This
observation has significance for the formulation of new theories (such as
quantum gravity theories) as it puts a constraint on the kinematics, if the
quantum/classical correspondence principle is to be preserved. Consequences for
quantum gravity, particularly for Lorentz symmetry and the idea of "emergent
geometry", are discussed.Comment: 35 pages (29 pages main body), two figure
- âŚ