114 research outputs found
Frontoparietal function in young people with dysthymic disorder (DSM-5: Persistent depressive disorder) during spatial working memory
Background Dysthymic disorder (DD) is a depressive disorder characterised by persistent low and/or irritable mood and has been identified as a major risk factor for developing major depressive disorder (MDD). MDD and DD have been associated with executive function difficulties of working memory and attention. Little is known about how executive function networks in the brain are affected in children and adolescents with MDD and even less in DD. This study used fMRI and two spatial working memory paradigms to investigate associated brain function in young people with DD and an age-, gender- and IQ- matched typically developing group. Methods Nineteen male patients with DD (mean age 11.2±1.5 years) diagnosed according to DSM-IV criteria and 16 typically developing boys (mean age 10.5±1.1 years) performed a mental rotation and a delay-match to sample (DMTS) task while undergoing fMRI. All participants were medication-naïve at the time of testing. Results Compared to typically developing young people, the DD group showed less activation in left frontal regions including left ventro- and dorsolateral prefrontal cortices (PFC) during mental rotation. Medial frontal regions including dorsomedial PFC, anterior cingulate cortex and frontal pole also showed relatively reduced activation. During the DMTS task patients showed significantly more activation in the right precuneus and posterior cingulate cortex. Limitations This was a cross-sectional study with a small sample limiting the generalizability of the results. Conclusions The results complement previous findings in adults with MDD that have shown differential activation of left PFC regions during working memory tasks. Additionally, altered function of cortical midline structures in young patients with DD was identified. This supports findings in children, adolescents and adults with MDD suggesting that the pathophysiology of depressive disorders extends to DD as a risk factor for MDD and exhibits continuity over the lifespan
Active Galactic Nuclei in Groups and Clusters of Galaxies: Detection and Host Morphology
The incidence and properties of Active Galactic Nuclei (AGN) in the field,
groups, and clusters can provide new information about how these objects are
triggered and fueled, similar to how these environments have been employed to
study galaxy evolution. We have obtained new XMM-Newton observations of seven
X-ray selected groups and poor clusters with 0.02 < z < 0.06 for comparison
with previous samples that mostly included rich clusters and optically-selected
groups. Our final sample has ten groups and six clusters in this low-redshift
range (split at a velocity dispersion of km/s). We find that the
X-ray selected AGN fraction increases from in clusters to for the
groups (85% significance), or a factor of two, for AGN above an 0.3-8keV X-ray
luminosity of erg/s hosted by galaxies more luminous than .
The trend is similar, although less significant, for a lower-luminosity host
threshold of mag. For many of the groups in the sample we have also
identified AGN via standard emission-line diagnostics and find that these AGN
are nearly disjoint from the X-ray selected AGN. Because there are substantial
differences in the morphological mix of galaxies between groups and clusters,
we have also measured the AGN fraction for early-type galaxies alone to
determine if the differences are directly due to environment, or indirectly due
to the change in the morphological mix. We find that the AGN fraction in
early-type galaxies is also lower in clusters compared to
for the groups (92% significance), a result consistent with the hypothesis that
the change in AGN fraction is directly connected to environment.Comment: 18 pages, 9 figures; accepted by The Astrophysical Journal; for
higher-resolution versions of some figures, see
http://u.arizona.edu/~tjarnold/Arnold09
Host Galaxies of Luminous Type 2 Quasars at z ~ 0.5
We present deep Gemini GMOS optical spectroscopy of nine luminous quasars at
redshifts z ~ 0.5, drawn from the SDSS type 2 quasar sample. Our targets were
selected to have high intrinsic luminosities (M_V < -26 mag) as indicated by
the [O III] 5007 A emission-line luminosity (L_[O III]). Our sample has a
median black hole mass of ~ 10^8.8 M_sun inferred assuming the local
M_BH-sigma_* relation and a median Eddington ratio of ~ 0.7, using stellar
velocity dispersions sigma_* measured from the G band. We estimate the
contamination of the stellar continuum from scattered quasar light based on the
strength of broad H-beta, and provide an empirical calibration of the
contamination as a function of L_[O III]; the scattered light fraction is ~ 30%
of L_5100 for objects with L_[O III] = 10^9.5 L_sun. Population synthesis
indicates that young post-starburst populations (< 0.1 Gyr) are prevalent in
luminous type 2 quasars, in addition to a relatively old population (> 1 Gyr)
which dominates the stellar mass. Broad emission complexes around He II 4686 A
with luminosities up to 10^8.3 L_sun are unambiguously detected in three out of
the nine targets, indicative of Wolf-Rayet populations. Population synthesis
shows that ~ 5-Myr post-starburst populations contribute substantially to the
luminosities (> 50% of L_5100) of all three objects with Wolf-Rayet detections.
We find two objects with double cores and four with close companions. Our
results may suggest that luminous type 2 quasars trace an early stage of galaxy
interaction, perhaps responsible for both the quasar and the starburst
activity.Comment: 20 pages, 13 figures, 7 tables; accepted to Ap
Theory of mind mediates the prospective relationship between abnormal social brain network morphology and chronic behavior problems after pediatric traumatic brain injury
Childhood and adolescence coincide with rapid maturation and synaptic reorganization of distributed neural networks that underlie complex cognitive-affective behaviors. These regions, referred to collectively as the ‘social brain network’ (SBN) are commonly vulnerable to disruption from pediatric traumatic brain injury (TBI); however, the mechanisms that link morphological changes in the SBN to behavior problems in this population remain unclear. In 98 children and adolescents with mild to severe TBI, we acquired 3D T1-weighted MRIs at 2–8 weeks post-injury. For comparison, 33 typically developing controls of similar age, sex and education were scanned. All participants were assessed on measures of Theory of Mind (ToM) at 6 months post-injury and parents provided ratings of behavior problems at 24-months post-injury. Severe TBI was associated with volumetric reductions in the overall SBN package, as well as regional gray matter structural change in multiple component regions of the SBN. When compared with TD controls and children with milder injuries, the severe TBI group had significantly poorer ToM, which was associated with more frequent behavior problems and abnormal SBN morphology. Mediation analysis indicated that impaired theory of mind mediated the prospective relationship between abnormal SBN morphology and more frequent chronic behavior problems. Our findings suggest that sub-acute alterations in SBN morphology indirectly contribute to long-term behavior problems via their influence on ToM. Volumetric change in the SBN and its putative hub regions may represent useful imaging biomarkers for prediction of post-acute social cognitive impairment, which may in turn elevate risk for chronic behavior problems
Developmental brain trajectories in children with ADHD and controls: a longitudinal neuroimaging study
BACKGROUND: The symptom profile and neuropsychological functioning of individuals with Attention Deficit/Hyperactivity Disorder (ADHD), change as they enter adolescence. It is unclear whether variation in brain structure and function parallels these changes, and also whether deviations from typical brain development trajectories are associated with differential outcomes. This paper describes the Neuroimaging of the Children\u27s Attention Project (NICAP), a comprehensive longitudinal multimodal neuroimaging study. Primary aims are to determine how brain structure and function change with age in ADHD, and whether different trajectories of brain development are associated with variations in outcomes including diagnostic persistence, and academic, cognitive, social and mental health outcomes. METHODS/DESIGN: NICAP is a multimodal neuroimaging study in a community-based cohort of children with and without ADHD. Approximately 100 children with ADHD and 100 typically developing controls will be scanned at a mean age of 10 years (range; 9-11years) and will be re-scanned at two 18-month intervals (ages 11.5 and 13 years respectively). Assessments include a structured diagnostic interview, parent and teacher questionnaires, direct child cognitive/executive functioning assessment and magnetic resonance imaging (MRI). MRI acquisition techniques, collected at a single site, have been selected to provide optimized information concerning structural and functional brain development. DISCUSSION: This study will allow us to address the primary aims by describing the neurobiological development of ADHD and elucidating brain features associated with differential clinical/behavioral outcomes. NICAP data will also be explored to assess the impact of sex, ADHD presentation, ADHD severity, comorbidities and medication use on brain development trajectories. Establishing which brain regions are associated with differential clinical outcomes, may allow us to improve predictions about the course of ADHD
Uncovering the neuroanatomical correlates of cognitive, affective and conative theory of mind in paediatric traumatic brain injury: a neural systems perspective
Deficits in theory of mind (ToM) are common after neurological insult acquired in the first and second decade of life, however the contribution of large-scale neural networks to ToM deficits in children with brain injury is unclear. Using paediatric traumatic brain injury (TBI) as a model, this study investigated the sub-acute effect of paediatric traumatic brain injury on grey-matter volume of three large-scale, domain-general brain networks (the Default Mode Network, DMN; the Central Executive Network, CEN; and the Salience Network, SN), as well as two domain-specific neural networks implicated in social-affective processes (the Cerebro-Cerebellar Mentalizing Network, CCMN and the Mirror Neuron/Empathy Network, MNEN). We also evaluated prospective structure–function relationships between these large-scale neural networks and cognitive, affective and conative ToM. 3D T1- weighted magnetic resonance imaging sequences were acquired sub-acutely in 137 children [TBI: n = 103; typically developing (TD) children: n = 34]. All children were assessed on measures of ToM at 24-months post-injury. Children with severe TBI showed sub-acute volumetric reductions in the CCMN, SN, MNEN, CEN and DMN, as well as reduced grey-matter volumes of several hub regions of these neural networks. Volumetric reductions in the CCMN and several of its hub regions, including the cerebellum, predicted poorer cognitive ToM. In contrast, poorer affective and conative ToM were predicted by volumetric reductions in the SN and MNEN, respectively. Overall, results suggest that cognitive, affective and conative ToM may be prospectively predicted by individual differences in structure of different neural systems—the CCMN, SN and MNEN, respectively. The prospective relationship between cerebellar volume and cognitive ToM outcomes is a novel finding in our paediatric brain injury sample and suggests that the cerebellum may play a role in the neural networks important for ToM. These findings are discussed in relation to neurocognitive models of ToM. We conclude that detection of sub-acute volumetric abnormalities of large-scale neural networks and their hub regions may aid in the early identification of children at risk for chronic social-cognitive impairment
The UV-Optical Color Dependence of Galaxy Clustering in the Local Universe
We measure the UV-optical color dependence of galaxy clustering in the local
universe. Using the clean separation of the red and blue sequences made
possible by the NUV - r color-magnitude diagram, we segregate the galaxies into
red, blue and intermediate "green" classes. We explore the clustering as a
function of this segregation by removing the dependence on luminosity and by
excluding edge-on galaxies as a means of a non-model dependent veto of highly
extincted galaxies. We find that \xi (r_p, \pi) for both red and green galaxies
shows strong redshift space distortion on small scales -- the "finger-of-God"
effect, with green galaxies having a lower amplitude than is seen for the red
sequence, and the blue sequence showing almost no distortion. On large scales,
\xi (r_p, \pi) for all three samples show the effect of large-scale streaming
from coherent infall. On scales 1 Mpc/h < r_p < 10 Mpc/h, the projected
auto-correlation function w_p(r_p) for red and green galaxies fits a power-law
with slope \gamma ~ 1.93 and amplitude r_0 ~ 7.5 and 5.3, compared with \gamma
~ 1.75 and r_0 ~ 3.9 Mpc/h for blue sequence galaxies. Compared to the
clustering of a fiducial L* galaxy, the red, green, and blue have a relative
bias of 1.5, 1.1, and 0.9 respectively. The w_p(r_p) for blue galaxies display
an increase in convexity at ~ 1 Mpc/h, with an excess of large scale
clustering. Our results suggest that the majority of blue galaxies are likely
central galaxies in less massive halos, while red and green galaxies have
larger satellite fractions, and preferentially reside in virialized structures.
If blue sequence galaxies migrate to the red sequence via processes like
mergers or quenching that take them through the green valley, such a
transformation may be accompanied by a change in environment in addition to any
change in luminosity and color.Comment: accepted by MNRA
Baryon Acoustic Oscillations in the Sloan Digital Sky Survey Data Release 7 Galaxy Sample
The spectroscopic Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) galaxy
sample represents the final set of galaxies observed using the original SDSS
target selection criteria. We analyse the clustering of galaxies within this
sample, including both the Luminous Red Galaxy (LRG) and Main samples, and also
include the 2-degree Field Galaxy Redshift Survey (2dFGRS) data. Baryon
Acoustic Oscillations are observed in power spectra measured for different
slices in redshift; this allows us to constrain the distance--redshift relation
at multiple epochs. We achieve a distance measure at redshift z=0.275, of
r_s(z_d)/D_V(0.275)=0.1390+/-0.0037 (2.7% accuracy), where r_s(z_d) is the
comoving sound horizon at the baryon drag epoch,
D_V(z)=[(1+z)^2D_A^2cz/H(z)]^(1/3), D_A(z) is the angular diameter distance and
H(z) is the Hubble parameter. We find an almost independent constraint on the
ratio of distances D_V(0.35)/D_V(0.2)=1.736+/-0.065, which is consistent at the
1.1sigma level with the best fit Lambda-CDM model obtained when combining our
z=0.275 distance constraint with the WMAP 5-year data. The offset is similar to
that found in previous analyses of the SDSS DR5 sample, but the discrepancy is
now of lower significance, a change caused by a revised error analysis and a
change in the methodology adopted, as well as the addition of more data. Using
WMAP5 constraints on Omega_bh^2 and Omega_ch^2, and combining our BAO distance
measurements with those from the Union Supernova sample, places a tight
constraint on Omega_m=0.286+/-0.018 and H_0 = 68.2+/-2.2km/s/Mpc that is robust
to allowing curvature and non-Lambda dark energy. This result is independent of
the behaviour of dark energy at redshifts greater than those probed by the BAO
and supernova measurements. (abridged)Comment: 22 pages, 16 figures, minor changes to match version published in
MNRA
Star formation in quasar hosts and the origin of radio emission in radio-quiet quasars
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record [Nadia L. Zakamska, et al., 'Star formation in quasar hosts and the origin of radio emission in radio-quiet quasars', MNRAS, 455(4): 4191-4211, first published online December 4, 2015, is available online via doi: 10.1093/mnras/stv2571 Published by Oxford University Press on behalf of the Royal Astronomical Society. Copyright 2015 The AuthorsRadio emission from radio-quiet quasars may be due to star formation in the quasar host galaxy, to a jet launched by the supermassive black hole, or to relativistic particles accelerated in a wide-angle radiatively driven outflow. In this paper, we examine whether radio emission from radio-quiet quasars is a byproduct of star formation in their hosts. To this end, we use infrared spectroscopy and photometry from Spitzer and Herschel to estimate or place upper limits on star formation rates in hosts of ∼300 obscured and unobscured quasars at z < 1. We find that low-ionization forbidden emission lines such as [Ne II] and [Ne III] are likely dominated by quasar ionization and do not provide reliable star formation diagnostics in quasar hosts, while polycyclic aromatic hydrocarbon (PAH) emission features may be suppressed due to the destruction of PAH molecules by the quasar radiation field. While the bolometric luminosities of our sources are dominated by the quasars, the 160 μm fluxes are likely dominated by star formation, but they too should be used with caution. We estimate median star formation rates to be 6–29 M yr−1, with obscured quasars at the high end of this range. This star formation rate is insufficient to explain the observed radio emission from quasars by an order of magnitude, with log (Lradio, obs/Lradio, SF) = 0.6–1.3 depending on quasar type and star formation estimator. Although radio-quiet quasars in our sample lie close to the 8–1000 μm infrared/radio correlation characteristic of the star-forming galaxies, both their infrared emission and their radio emission are dominated by the quasar activity, not by the host galaxy.Peer reviewedFinal Published versio
Observing the Evolution of the Universe
How did the universe evolve? The fine angular scale (l>1000) temperature and
polarization anisotropies in the CMB are a Rosetta stone for understanding the
evolution of the universe. Through detailed measurements one may address
everything from the physics of the birth of the universe to the history of star
formation and the process by which galaxies formed. One may in addition track
the evolution of the dark energy and discover the net neutrino mass.
We are at the dawn of a new era in which hundreds of square degrees of sky
can be mapped with arcminute resolution and sensitivities measured in
microKelvin. Acquiring these data requires the use of special purpose
telescopes such as the Atacama Cosmology Telescope (ACT), located in Chile, and
the South Pole Telescope (SPT). These new telescopes are outfitted with a new
generation of custom mm-wave kilo-pixel arrays. Additional instruments are in
the planning stages.Comment: Science White Paper submitted to the US Astro2010 Decadal Survey.
Full list of 177 author available at http://cmbpol.uchicago.ed
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