8 research outputs found
Disrupted Resting-State Functional Connectivity in Progressive Supranuclear Palsy
BACKGROUND AND PURPOSE: Studies on functional connectivity in progressive supranuclear palsy have been restricted to the thalamus and midbrain tegmentum. The present study aims to evaluate functional connectivity abnormalities of the subcortical structures in these patients. Functional connectivity will be correlated with motor and nonmotor symptoms of the disease. MATERIALS AND METHODS: Nineteen patients with progressive supranuclear palsy (mean age, 70.93 ± 5.19 years) and 12 age-matched healthy subjects (mean age, 69.17 ± 5.20 years) underwent multimodal MR imaging, including fMRI at rest, 3D T1-weighted imaging, and DTI. fMRI data were processed with fMRI of the Brain Software Library tools by using the dorsal midbrain tegmentum, thalamus, caudate nucleus, putamen, and pallidum as seed regions. RESULTS: Patients had lower functional connectivity than healthy subjects in all 5 resting-state networks, mainly involving the basal ganglia, thalamus, anterior cingulate, dorsolateral prefrontal and temporo-occipital cortices, supramarginal gyrus, supplementary motor area, and cerebellum. Compared with healthy subjects, patients also displayed subcortical atrophy and DTI abnormalities. Decreased thalamic functional connectivity correlated with clinical scores, as assessed by the Hoehn and Yahr Scale and by the bulbar and mentation subitems of the Progressive Supranuclear Palsy Rating Scale. Decreased pallidum functional connectivity correlated with lower Mini-Mental State Examination scores; decreased functional connectivity in the dorsal midbrain tegmentum network correlated with lower scores in the Frontal Assessment Battery. CONCLUSIONS: The present study demonstrates a widespread disruption of cortical-subcortical connectivity in progressive supranuclear palsy and provides further insight into the pathophysiologic mechanisms of motor and cognitive impairment in this condition
Disrupted Resting-State Functional Connectivity in Progressive Supranuclear Palsy
BACKGROUND AND PURPOSE: Studies on functional connectivity in progressive supranuclear palsy have been restricted to the thalamus and midbrain tegmentum. The present study aims to evaluate functional connectivity abnormalities of the subcortical structures in these patients. Functional connectivity will be correlated with motor and nonmotor symptoms of the disease. MATERIALS AND METHODS: Nineteen patients with progressive supranuclear palsy (mean age, 70.93 ± 5.19 years) and 12 age-matched healthy subjects (mean age, 69.17 ± 5.20 years) underwent multimodal MR imaging, including fMRI at rest, 3D T1-weighted imaging, and DTI. fMRI data were processed with fMRI of the Brain Software Library tools by using the dorsal midbrain tegmentum, thalamus, caudate nucleus, putamen, and pallidum as seed regions. RESULTS: Patients had lower functional connectivity than healthy subjects in all 5 resting-state networks, mainly involving the basal ganglia, thalamus, anterior cingulate, dorsolateral prefrontal and temporo-occipital cortices, supramarginal gyrus, supplementary motor area, and cerebellum. Compared with healthy subjects, patients also displayed subcortical atrophy and DTI abnormalities. Decreased thalamic functional connectivity correlated with clinical scores, as assessed by the Hoehn and Yahr Scale and by the bulbar and mentation subitems of the Progressive Supranuclear Palsy Rating Scale. Decreased pallidum functional connectivity correlated with lower Mini-Mental State Examination scores; decreased functional connectivity in the dorsal midbrain tegmentum network correlated with lower scores in the Frontal Assessment Battery. CONCLUSIONS: The present study demonstrates a widespread disruption of cortical-subcortical connectivity in progressive supranuclear palsy and provides further insight into the pathophysiologic mechanisms of motor and cognitive impairment in this condition
Revisiting Generalized Chaplygin Gas as a Unified Dark Matter and Dark Energy Model
In this paper, we revisit generalized Chaplygin gas (GCG) model as a unified
dark matter and dark energy model. The energy density of GCG model is given as
,
where and are two model parameters which will be constrained by
type Ia supernova as standard candles, baryon acoustic oscillation as standard
rulers and the seventh year full WMAP data points. In this paper, we will not
separate GCG into dark matter and dark energy parts any more as adopted in the
literatures. By using Markov Chain Monte Carlo method, we find the result:
and .Comment: 6 pages, 4 figure
Contraints on unified models for dark matter and dark energy using H(z)
The differential age data of astrophysical objects that have evolved
passivelly during the history of the universe (e.g. red galaxies) allows to
test theoretical cosmological models through the predicted Hubble function
expressed in terms of the redshift , . We use the observational data
for to test unified scenarios for dark matter and dark energy.
Specifically, we focus our analysis on the Generalized Chaplygin Gas (GCG) and
the viscous fluid (VF) models. For the GCG model, it is shown that the unified
scenario for dark energy and dark matter requires some priors. For the VF model
we obtain estimations for the free parameters that may be compared with further
analysis mainly at perturbative level.Comment: Latex file, 10 pages, 19 figures in eps format. Accepted for
publication in European Journal of Physics
Spherical collapse of a unified dark fluid with constant adiabatic sound speed
In this paper, we test the spherical collapse of a unified dark fluid (UDF)
which has constant adiabatic sound speed. By choosing the different values of
model parameters and , we show the nonlinear collapse for UDF and
baryons which are considered for their formation of the large scale structure
of our Universe. The analyzed results show that larger values of and
make the structure formation faster and earlier.Comment: 5 pages, 4 figures, accepted for publication in Eur. Phys. J.
Does Chaplygin gas have salvation?
Campos JP, Fabris JC, Perez R, Piattella OF, Velten H. Does Chaplygin gas have salvation? European Physical Journal C. 2013;73(4): 2357.We investigate the unification scenario provided by the generalized Chaplygin gas model (a perfect fluid characterized by an equation of state p = -A/rho(alpha)). Our concerns lie with a possible tension existing between background kinematic tests and those related to the evolution of small perturbations. We analyze data from the observation of the differential age of the universe, type Ia supernovae, baryon acoustic oscillations, and the position of the first peak of the angular spectrum of the cosmic background radiation. We show that these tests favor negative values of the parameter alpha: we find alpha = -0.089(-0.128)(+0.161) at the 2 sigma level and that alpha < 0 with 85 % confidence. These would correspond to negative values of the square speed of sound which are unacceptable from the point of view of structure formation. We discuss a possible solution to this problem, when the generalized Chaplygin gas is framed in the modified theory of gravity proposed by Rastall. We show that a fluid description within this theory does not serve the purpose, but it is necessary to frame the generalized Chaplygin gas in a scalar field theory. Finally, we address the standard general relativistic unification picture provided by the generalized Chaplygin gas in the case alpha = 0: this is usually considered to be undistinguishable from the standard Lambda CDM model, but we show that the evolution of small perturbations, governed by the Meszaros equation, is indeed different and the formation of sub-horizon GCG matter halos may be importantly affected in comparison with the Lambda CDM scenario