61 research outputs found
The role of the ventrolateral frontal cortex in inhibitory oculomotor control
It has been proposed that the inferior/ventrolateral frontal cortex plays a critical role in the inhibitory control of action during cognitive tasks.However, the contribution of this region to the control of eye movements has not been clearly established.Here, we describe the performance of a group of 23 frontal lobe damaged patients in an oculomotor rule switching task for which the association between a centrally presented visual cue and the
direction of a saccade could change from trial to trial. A subset of 16 patients also completed the standard
antisaccade task.Ventrolateral damage was found to be a significant predictor of errors in both tasks. Analysis
of the rate at which patients corrected errors in the rule switching task also revealed an important dissociation
between left and right hemisphere damaged patients.Whilst patients with left ventrolateral damage usually corrected
response errors with secondary saccades, those with right hemisphere lesions often failed to do so.
The results suggest that the inferior frontal cortex forms part of a wider frontal network mediating inhibitory
control over stimulus elicited eye movements. The critical role played by the right ventrolateral region in
cognitive tasks may arise due to an additional functional specialization for the monitoring and updating of task rules
Mergers and Typical Black Hole Microstates
We use mergers of microstates to obtain the first smooth horizonless
microstate solutions corresponding to a BPS three-charge black hole with a
classically large horizon area. These microstates have very long throats, that
become infinite in the classical limit; nevertheless, their curvature is
everywhere small. Having a classically-infinite throat makes these microstates
very similar to the typical microstates of this black hole. A rough CFT
analysis confirms this intuition, and indicates a possible class of dual CFT
microstates.
We also analyze the properties and the merging of microstates corresponding
to zero-entropy BPS black holes and black rings. We find that these solutions
have the same size as the horizon size of their classical counterparts, and we
examine the changes of internal structure of these microstates during mergers.Comment: 49 pages, 5 figures. v2 references adde
Black Rings in Taub-NUT
We construct the most generic three-charge, three-dipole-charge, BPS
black-ring solutions in a Taub-NUT background. These solutions depend on seven
charges and six moduli, and interpolate between a four-dimensional black hole
and a five-dimensional black ring. They are also instrumental in determining
the correct microscopic description of the five-dimensional BPS black rings.Comment: 16 pages, harvma
Bubbles on Manifolds with a U(1) Isometry
We investigate the construction of five-dimensional, three-charge
supergravity solutions that only have a rotational U(1) isometry. We show that
such solutions can be obtained as warped compactifications with a singular
ambi-polar hyper-Kahler base space and singular warp factors. We show that the
complete solution is regular around the critical surface of the ambi-polar
base. We illustrate this by presenting the explicit form of the most general
supersymmetric solutions that can be obtained from an Atiyah-Hitchin base space
and its ambi-polar generalizations. We make a parallel analysis using an
ambi-polar generalization of the Eguchi-Hanson base space metric. We also show
how the bubbling procedure applied to the ambi-polar Eguchi-Hanson metric can
convert it to a global AdS_2xS^3 compactification.Comment: 33 pages, 5 figures, LaTeX; references adde
Supersymmetric Charged Clouds in AdS_5
We consider supersymmetric holographic flows that involve background gauge
fields dual to chemical potentials in the boundary field theory. We use a
consistent truncation of gauged N=8 supergravity in five dimensions and we give
a complete analysis of the supersymmetry conditions for a large family of
flows. We examine how the well-known supersymmetric flow between two fixed
points is modified by the presence of the chemical potentials and this yields a
new, completely smooth, solution that interpolates between two global AdS
spaces of different radii and with different values of the chemical potential.
We also examine some black-hole-like singular flows and a new
non-supersymmetric black hole solution. We comment on the interpretation of our
new solutions in terms of giant gravitons and discuss the implications of our
work for finding black-hole solutions in AdS geometries.Comment: 31 pages, 6 figures; minor corrections, updated reference
Supergravity Solutions from Floating Branes
We solve the equations of motion of five-dimensional ungauged supergravity
coupled to three U(1) gauge fields using a floating-brane Ansatz in which the
electric potentials are directly related to the gravitational warp factors. We
find a new class of non-BPS solutions, that can be obtained linearly starting
from an Euclidean four-dimensional Einstein-Maxwell base. This class - the
largest known so far - reduces to the BPS and almost-BPS solutions in certain
limits. We solve the equations explicitly when the base space is given by the
Israel-Wilson metric, and obtain solutions describing non-BPS D6 and anti-D6
branes kept in equilibrium by flux. We also examine the action of spectral flow
on solutions with an Israel-Wilson base and show that it relates these
solutions to almost-BPS solutions with a Gibbons-Hawking base.Comment: 24 pages, 1 figur
A (Running) Bolt for New Reasons
We construct a four-parameter family of smooth, horizonless, stationary
solutions of ungauged five-dimensional supergravity by using the
four-dimensional Euclidean Schwarzschild metric as a base space and
"magnetizing" its bolt. We then generalize this to a five-parameter family
based upon the Euclidean Kerr-Taub-Bolt. These "running Bolt" solutions are
necessarily non-static. They also have the same charges and mass as a
non-extremal black hole with a classically-large horizon area. Moreover, in a
certain regime their mass can decrease as their charges increase. The existence
of these solutions supports the idea that the singularities of non-extremal
black holes are resolved by low-mass modes that correct the singularity of the
classical black hole solution on large (horizon-sized) scales.Comment: 25 pages, 3 figures, LaTeX; v2: minor changes, references adde
Multi-Center non-BPS Black Holes - the Solution
We construct multi-center, non-supersymmetric four-dimensional solutions
describing a rotating anti-D6-D2 black hole and an arbitrary number of D4-D2-D0
black holes in a line. These solutions correspond to an arbitrary number of
extremal non-BPS black rings in a Taub-NUT space with a rotating three-charge
black hole in the middle. The positions of the centers are determined by
solving a set of "bubble" or "integrability" equations that contain cubic
polynomials of the inter-center distance, and that allow scaling solutions even
when the total four-dimensional angular momentum of the scaling centers is
non-zero.Comment: 16 pages, LaTe
An Infinite-Dimensional Family of Black-Hole Microstate Geometries
We construct the first explicit, smooth, horizonless black-hole microstate
geometry whose moduli space is described by an arbitrary function of one
variable and is thus infinite-dimensional. This is achieved by constructing the
scalar Green function on a simple D6 anti-D6 background, and using this Green
function to obtain the fully back-reacted solution for a supertube with varying
charge density in this background. We show that this supertube can store
parametrically more entropy than in flat space, confirming the entropy
enhancement mechanism that was predicted using brane probes. We also show that
all the local properties of the fully back-reacted solution can, in fact, be
obtained using the DBI action of an appropriate brane probe. In particular, the
supergravity and the DBI analysis yield identical functional bubble equations
that govern the relative locations of the centers. This indicates that there is
a non-renormalization theorem that protects these functional equations as one
moves in moduli space. Our construction creates configurations that are beyond
the scope of recent arguments that appear to put strong limits on the entropy
that can be found in smooth supergravity solutions.Comment: 46 pages, 1 figure, LaTe
Three novel mutations in KIF21A highlight the importance of the third coiled-coil stalk domain in the etiology of CFEOM1
<p>Abstract</p> <p>Background</p> <p>Congenital fibrosis of the extraocular muscles types 1 and 3 (CFEOM1/CFEOM3) are autosomal dominant strabismus disorders that appear to result from maldevelopment of ocular nuclei and nerves. We previously reported that most individuals with CFEOM1 and rare individuals with CFEOM3 harbor heterozygous mutations in <it>KIF21A</it>. <it>KIF21A </it>encodes a kinesin motor involved in anterograde axonal transport, and the familial and <it>de novo </it>mutations reported to date predictably alter one of only a few KIF21A amino acids – three within the third coiled-coil region of the stalk and one in the distal motor domain, suggesting they result in altered KIF21A function. To further define the spectrum of <it>KIF21A </it>mutations in CFEOM we have now identified all CFEOM probands newly enrolled in our study and determined if they harbor mutations in <it>KIF21A</it>.</p> <p>Results</p> <p>Sixteen CFEOM1 and 29 CFEOM3 probands were studied. Three previously unreported <it>de novo </it>KIF21A mutations were identified in three CFEOM1 probands, all located in the same coiled-coil region of the stalk that contains all but one of the previously reported mutations. Eight additional CFEOM1 probands harbored three of the mutations previously reported in <it>KIF21A</it>; seven had one of the two most common mutations, while one harbored the mutation in the distal motor domain. No mutation was detected in 5 CFEOM1 or any CFEOM3 probands.</p> <p>Conclusion</p> <p>Analysis of sixteen CFEOM1 probands revealed three novel <it>KIF21A </it>mutations and confirmed three reported mutations, bringing the total number of reported <it>KIF21A </it>mutations in CFEOM1 to 11 mutations among 70 mutation positive probands. All three new mutations alter amino acids in heptad repeats within the third coiled-coil region of the KIF21A stalk, further highlighting the importance of alterations in this domain in the etiology of CFEOM1.</p
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