272 research outputs found
Isolation rearing impairs novel object recognition and attentional set shifting performance in female rats
YesIt has been suggested that the isolation rearing paradigm models certain
aspects of schizophrenia symptomatology. This study aimed to investigate
whether isolation rearing impairs rats’ performance in two models of
cognition: the novel object recognition (NOR) and attentional set-shifting
tasks, tests of episodic memory and executive function, respectively.
Two cohorts of female Hooded-Lister rats were used in these experiments.
Animals were housed in social isolation or in groups of five from weaning,
post-natal day 28. The first cohort was tested in the NOR test with
inter-trial intervals (ITIs) of 1 min up to 6 h. The second cohort was
trained and tested in the attentional set-shifting task. In the NOR test,
isolates were only able to discriminate between the novel and familiar
objects up to 1-h ITI, whereas socially reared animals remembered the
familiar object up to a 4-h ITI. In the attentional set-shifting task,
isolates were significantly and selectively impaired in the
extra-dimensional shift phase of the task (P < 0.01). Rats reared in
isolation show impaired episodic memory in the NOR task and reduced
ability to shift attention between stimulus dimensions in the attentional
set-shifting task. Because schizophrenic patients show similar deficits in
performance in these cognitive domains, these data further support
isolation rearing as a putative preclinical model of the cognitive deficits
associated with schizophrenia
Black Hole Emission in String Theory and the String Phase of Black Holes
String theory properly describes black-hole evaporation. The quantum string
emission by Black Holes is computed. The black-hole temperature is the Hawking
temperature in the semiclassical quantum field theory (QFT) regime and becomes
the intrinsic string temperature, T_s, in the quantum (last stage) string
regime. The QFT-Hawking temperature T_H is upper bounded by the string
temperature T_S. The black hole emission spectrum is an incomplete gamma
function of (T_H - T_S). For T_H << T_S, it yields the QFT-Hawking emission.
For T_H \to T_S, it shows highly massive string states dominate the emission
and undergo a typical string phase transition to a microscopic `minimal' black
hole of mass M_{\min} or radius r_{\min} (inversely proportional to T_S) and
string temperature T_S. The string back reaction effect (selfconsistent black
hole solution of the semiclassical Einstein equations) is computed. Both, the
QFT and string black hole regimes are well defined and bounded.The string
`minimal' black hole has a life time tau_{min} simeq (k_B c)/(G hbar [T_S]^3).
The semiclassical QFT black hole (of mass M and temperature T_H) and the string
black hole (of mass M_{min} and temperature T_S) are mapped one into another by
a `Dual' transform which links classical/QFT and quantum string regimes.Comment: LaTex, 22 pages, Lectures delivered at the Chalonge School, Nato ASI:
Phase Transitions in the Early Universe: Theory and Observations. To appear
in the Proceedings, Editors H. J. de Vega, I. Khalatnikov, N. Sanchez.
(Kluwer Pub
Epigenome-wide association study in the European Prospective Investigation into Cancer and Nutrition (EPIC-Turin) identifies novel genetic loci associated with smoking
Asymmetric c-fos expression in the ventral orbital cortex is associated with impaired reversal learning in a right-sided neuropathy
BACKGROUND:
Recently we showed that unilateral peripheral neuropathic lesions impacted differentially on rat's emotional/cognitive behavior depending on its left/right location; importantly, this observation recapitulates clinical reports. The prefrontal cortex (PFC), a brain region morphofunctionally affected in chronic pain conditions, is involved in the modulation of both emotion and executive function and displays functional lateralization. To test whether the PFC is involved in the lateralization bias associated with left/right pain, c-fos expression in medial and orbital areas was analyzed in rats with an unilateral spared nerve injury neuropathy installed in the left or in the right side after performing an attentional set-shifting, a strongly PFC-dependent task.
RESULTS:
SNI-R animals required more trials to successfully terminate the reversal steps of the attentional set-shifting task. A generalized increase of c-fos density in medial and orbital PFC (mPFC/OFC), irrespectively of the hemisphere, was observed in both SNI-L and SNI-R. However, individual laterality indexes revealed that contrary to controls and SNI-L, SNI-R animals presented a leftward shift in c-fos density in the ventral OFC (VO). None of these effects were observed in the neighboring primary motor area.
CONCLUSIONS:
Our results demonstrate that chronic neuropathic pain is associated with a bilateral mPFC and OFC hyperactivation. We hypothesize that the impaired performance of SNI-R animals is associated with a left/right activity inversion in the VO, whose functional integrity is critical for reversal learning.This work was granted by the Portuguese Science Foundation (FCT) project PTDC/SAU-NEU/108557/2008 and grant SFRH/BPD/80118/2011
Vacuum Ambiguity in de Sitter Space at Strong Coupling
It is well known that in the weak coupling regime, quantum field theories in
de Sitter space do not have a unique vacuum, but a class of vacua parametrized
by a complex parameter , i.e., the so-called -vacua. In this
article, using gauge/gravity duality, we calculate the symmetric two-point
function of strongly coupled supersymmetric Yang-Mills theory on
. We find that there is a class of de Sitter invariant vacua,
parametrized by a set of complex parameters .Comment: 17 pages in JHEP style, references adde
No chiral truncation of quantum log gravity?
At the classical level, chiral gravity may be constructed as a consistent
truncation of a larger theory called log gravity by requiring that left-moving
charges vanish. In turn, log gravity is the limit of topologically massive
gravity (TMG) at a special value of the coupling (the chiral point). We study
the situation at the level of linearized quantum fields, focussing on a unitary
quantization. While the TMG Hilbert space is continuous at the chiral point,
the left-moving Virasoro generators become ill-defined and cannot be used to
define a chiral truncation. In a sense, the left-moving asymptotic symmetries
are spontaneously broken at the chiral point. In contrast, in a non-unitary
quantization of TMG, both the Hilbert space and charges are continuous at the
chiral point and define a unitary theory of chiral gravity at the linearized
level.Comment: 20 pages, no figures, references adde
Nonminimal Couplings in the Early Universe: Multifield Models of Inflation and the Latest Observations
Models of cosmic inflation suggest that our universe underwent an early phase
of accelerated expansion, driven by the dynamics of one or more scalar fields.
Inflationary models make specific, quantitative predictions for several
observable quantities, including particular patterns of temperature anistropies
in the cosmic microwave background radiation. Realistic models of high-energy
physics include many scalar fields at high energies. Moreover, we may expect
these fields to have nonminimal couplings to the spacetime curvature. Such
couplings are quite generic, arising as renormalization counterterms when
quantizing scalar fields in curved spacetime. In this chapter I review recent
research on a general class of multifield inflationary models with nonminimal
couplings. Models in this class exhibit a strong attractor behavior: across a
wide range of couplings and initial conditions, the fields evolve along a
single-field trajectory for most of inflation. Across large regions of phase
space and parameter space, therefore, models in this general class yield robust
predictions for observable quantities that fall squarely within the "sweet
spot" of recent observations.Comment: 17pp, 2 figs. References added to match the published version.
Published in {\it At the Frontier of Spacetime: Scalar-Tensor Theory, Bell's
Inequality, Mach's Principle, Exotic Smoothness}, ed. T. Asselmeyer-Maluga
(Springer, 2016), pp. 41-57, in honor of Carl Brans's 80th birthda
A de Sitter Hoedown
Rotating black holes in de Sitter space are known to have interesting limits
where the temperatures of the black hole and cosmological horizon are equal. We
give a complete description of the thermal phase structure of all allowed
rotating black hole configurations. Only one configuration, the rotating Nariai
limit, has the black hole and cosmological horizons both in thermal and
rotational equilibrium, in that both the temperatures and angular velocities of
the two horizons coincide. The thermal evolution of the spacetime is shown to
lead to the pure de Sitter spacetime, which is the most entropic configuration.
We then provide a comprehensive study of the wave equation for a massless
scalar in the rotating Nariai geometry. The absorption cross section at the
black hole horizon is computed and a condition is found for when the scattering
becomes superradiant. The boundary-to-boundary correlators at finite
temperature are computed at future infinity. The quasinormal modes are obtained
in explicit form. Finally, we obtain an expression for the expectation value of
the number of particles produced at future infinity starting from a vacuum
state with no incoming particles at past infinity. Some of our results are used
to provide further evidence for a recent holographic proposal between the
rotating Nariai geometry and a two-dimensional conformal field theory.Comment: 35 + 1 pages, 9 figures; v3: typos correcte
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