108 research outputs found
Dynamic functional connectivity analysis reveals transient states of dysconnectivity in schizophrenia
Schizophrenia is a psychotic disorder characterized by functional dysconnectivity or abnormal integration between distant brain regions. Recent functional imaging studies have implicated large-scale thalamo-cortical connectivity as being disrupted in patients. However, observed connectivity differences in schizophrenia have been inconsistent between studies, with reports of hyperconnectivity and hypoconnectivity between the same brain regions. Using resting state eyes-closed functional imaging and independent component analysis on a multi-site data that included 151 schizophrenia patients and 163 age- and gender matched healthy controls, we decomposed the functional brain data into 100 components and identified 47 as functionally relevant intrinsic connectivity networks. We subsequently evaluated group differences in functional network connectivity, both in a static sense, computed as the pairwise Pearson correlations between the full network time courses (5.4minutes in length), and a dynamic sense, computed using sliding windows (44s in length) and k-means clustering to characterize five discrete functional connectivity states. Static connectivity analysis revealed that compared to healthy controls, patients show significantly stronger connectivity, i.e., hyperconnectivity, between the thalamus and sensory networks (auditory, motor and visual), as well as reduced connectivity (hypoconnectivity) between sensory networks from all modalities. Dynamic analysis suggests that (1), on average, schizophrenia patients spend much less time than healthy controls in states typified by strong, large-scale connectivity, and (2), that abnormal connectivity patterns are more pronounced during these connectivity states. In particular, states exhibiting corticalâsubcortical antagonism (anti-correlations) and strong positive connectivity between sensory networks are those that show the group differences of thalamic hyperconnectivity and sensory hypoconnectivity. Group differences are weak or absent during other connectivity states. Dynamic analysis also revealed hypoconnectivity between the putamen and sensory networks during the same states of thalamic hyperconnectivity; notably, this finding cannot be observed in the static connectivity analysis. Finally, in post-hoc analyses we observed that the relationships between sub-cortical low frequency power and connectivity with sensory networks is altered in patients, suggesting different functional interactions between sub-cortical nuclei and sensorimotor cortex during specific connectivity states. While important differences between patients with schizophrenia and healthy controls have been identified, one should interpret the results with caution given the history of medication in patients. Taken together, our results support and expand current knowledge regarding dysconnectivity in schizophrenia, and strongly advocate the use of dynamic analyses to better account for and understand functional connectivity differences.HighlightsâąStudied both static and dynamic connectivity changes in schizophrenia during restâąSmall but significant connectivity differences might be obscured in static analysis.âąPatients show significant differences in dwell times in multiple states.âąDisrupted thalamo-cortical connectivity in schizophrenia in a state-specific manne
Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
Data collected by the Pierre Auger Observatory through 31 August 2007 showed
evidence for anisotropy in the arrival directions of cosmic rays above the
Greisen-Zatsepin-Kuz'min energy threshold, \nobreak{eV}. The
anisotropy was measured by the fraction of arrival directions that are less
than from the position of an active galactic nucleus within 75 Mpc
(using the V\'eron-Cetty and V\'eron catalog). An updated
measurement of this fraction is reported here using the arrival directions of
cosmic rays recorded above the same energy threshold through 31 December 2009.
The number of arrival directions has increased from 27 to 69, allowing a more
precise measurement. The correlating fraction is , compared
with expected for isotropic cosmic rays. This is down from the early
estimate of . The enlarged set of arrival directions is
examined also in relation to other populations of nearby extragalactic objects:
galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in
hard X-rays by the Swift Burst Alert Telescope. A celestial region around the
position of the radiogalaxy Cen A has the largest excess of arrival directions
relative to isotropic expectations. The 2-point autocorrelation function is
shown for the enlarged set of arrival directions and compared to the isotropic
expectation.Comment: Accepted for publication in Astroparticle Physics on 31 August 201
Atmospheric effects on extensive air showers observed with the Surface Detector of the Pierre Auger Observatory
Atmospheric parameters, such as pressure (P), temperature (T) and density,
affect the development of extensive air showers initiated by energetic cosmic
rays. We have studied the impact of atmospheric variations on extensive air
showers by means of the surface detector of the Pierre Auger Observatory. The
rate of events shows a ~10% seasonal modulation and ~2% diurnal one. We find
that the observed behaviour is explained by a model including the effects
associated with the variations of pressure and density. The former affects the
longitudinal development of air showers while the latter influences the Moliere
radius and hence the lateral distribution of the shower particles. The model is
validated with full simulations of extensive air showers using atmospheric
profiles measured at the site of the Pierre Auger Observatory.Comment: 24 pages, 9 figures, accepted for publication in Astroparticle
Physic
Search for First Harmonic Modulation in the Right Ascension Distribution of Cosmic Rays Detected at the Pierre Auger Observatory
We present the results of searches for dipolar-type anisotropies in different
energy ranges above eV with the surface detector array of
the Pierre Auger Observatory, reporting on both the phase and the amplitude
measurements of the first harmonic modulation in the right-ascension
distribution. Upper limits on the amplitudes are obtained, which provide the
most stringent bounds at present, being below 2% at 99% for EeV
energies. We also compare our results to those of previous experiments as well
as with some theoretical expectations.Comment: 28 pages, 11 figure
Estradiol synthesis within the human brain
Estradiol biosynthesis is catalyzed by the enzyme aromatase, the product of the CYP19A1 gene. Aromatase is expressed in the brain, where it is involved not only in the control of neuroendocrine events and reproduction, but also in the regulation of neural development, synaptic plasticity and cell survival. In this review we summarize the existing data related with the detection of aromatase in human brain, with particular emphasis in the so-called ânon-primary reproductiveâ areas. Besides hypothalamus, amygdala and preoptic/septal areas, aromatase is expressed in certain regions of basal forebrain, cerebral cortex, hippocampus, thalamus, cerebellum and brainstem of the human brain. Aromatase in human brain is produced by neurons, but there is also an astrocyte subpopulation that constitutively expresses the enzyme. The use of different methodological approaches, including the in vivo analysis by positron emission tomography of human subjects, has permitted to draw a general map of human brain aromatase, but the detailed distribution map is still far to be completed. On the other hand, despite the fact that there is only one aromatase protein, there are multiple mRNA transcripts that differ in the 5'-untranslated region, where regulatory elements reside. To date, some of the aromatase transcripts characteristic of cerebral cortex, as well as of human cell lines of neural origin, have been identified. This characteristic may confer tissue or even region-specific regulation of the expression and therefore it is conceivable to develop selective aromatase modulators to regulate the expression of the enzyme in the human brai
Upper limit on the cosmic-ray photon fraction at EeV energies from the Pierre Auger Observatory
From direct observations of the longitudinal development of ultra-high energy
air showers performed with the Pierre Auger Observatory, upper limits of 3.8%,
2.4%, 3.5% and 11.7% (at 95% c.l.) are obtained on the fraction of cosmic-ray
photons above 2, 3, 5 and 10 EeV (1 EeV = 10^18 eV) respectively. These are the
first experimental limits on ultra-high energy photons at energies below 10
EeV. The results complement previous constraints on top-down models from array
data and they reduce systematic uncertainties in the interpretation of shower
data in terms of primary flux, nuclear composition and proton-air
cross-section.Comment: 20 pages, 7 figures, 2 tables. Minor changes. Accepted by
Astroparticle Physic
Investigation of hospital discharge cases and SARS-CoV-2 introduction into Lothian care homes
Background
The first epidemic wave of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) in Scotland resulted in high case numbers and mortality in care homes. In Lothian, over one-third of care homes reported an outbreak, while there was limited testing of hospital patients discharged to care homes.
Aim
To investigate patients discharged from hospitals as a source of SARS-CoV-2 introduction into care homes during the first epidemic wave.
Methods
A clinical review was performed for all patients discharges from hospitals to care homes from 1st March 2020 to 31st May 2020. Episodes were ruled out based on coronavirus disease 2019 (COVID-19) test history, clinical assessment at discharge, whole-genome sequencing (WGS) data and an infectious period of 14 days. Clinical samples were processed for WGS, and consensus genomes generated were used for analysis using Cluster Investigation and Virus Epidemiological Tool software. Patient timelines were obtained using electronic hospital records.
Findings
In total, 787 patients discharged from hospitals to care homes were identified. Of these, 776 (99%) were ruled out for subsequent introduction of SARS-CoV-2 into care homes. However, for 10 episodes, the results were inconclusive as there was low genomic diversity in consensus genomes or no sequencing data were available. Only one discharge episode had a genomic, time and location link to positive cases during hospital admission, leading to 10 positive cases in their care home.
Conclusion
The majority of patients discharged from hospitals were ruled out for introduction of SARS-CoV-2 into care homes, highlighting the importance of screening all new admissions when faced with a novel emerging virus and no available vaccine
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