3,642 research outputs found
Alterations in white matter microstructure in neurofibromatosis-1.
Neurofibromatosis (NF1) represents the most common single gene cause of learning disabilities. NF1 patients have impairments in frontal lobe based cognitive functions such as attention, working memory, and inhibition. Due to its well-characterized genetic etiology, investigations of NF1 may shed light on neural mechanisms underlying such difficulties in the general population or other patient groups. Prior neuroimaging findings indicate global brain volume increases, consistent with neural over-proliferation. However, little is known about alterations in white matter microstructure in NF1. We performed diffusion tensor imaging (DTI) analyses using tract-based spatial statistics (TBSS) in 14 young adult NF1 patients and 12 healthy controls. We also examined brain volumetric measures in the same subjects. Consistent with prior studies, we found significantly increased overall gray and white matter volume in NF1 patients. Relative to healthy controls, NF1 patients showed widespread reductions in white matter integrity across the entire brain as reflected by decreased fractional anisotropy (FA) and significantly increased absolute diffusion (ADC). When radial and axial diffusion were examined we found pronounced differences in radial diffusion in NF1 patients, indicative of either decreased myelination or increased space between axons. Secondary analyses revealed that FA and radial diffusion effects were of greatest magnitude in the frontal lobe. Such alterations of white matter tracts connecting frontal regions could contribute to the observed cognitive deficits. Furthermore, although the cellular basis of these white matter microstructural alterations remains to be determined, our findings of disproportionately increased radial diffusion against a background of increased white matter volume suggest the novel hypothesis that one potential alteration contributing to increased cortical white matter in NF1 may be looser packing of axons, with or without myelination changes. Further, this indicates that axial and radial diffusivity can uniquely contribute as markers of NF1-associated brain pathology in conjunction with the typically investigated measures
Testing the Flyby Anomaly with the GNSS Constellation
We propose the concept of a space mission to probe the so called flyby
anomaly, an unexpected velocity change experienced by some deep-space probes
using earth gravity assists. The key feature of this proposal is the use of
GNSS systems to obtain an increased accuracy in the tracking of the approaching
spacecraft, mainly near the perigee. Two low-cost options are also discussed to
further test this anomaly: an add-on to an existing spacecraft and a dedicated
mission.Comment: 8 pages, 1 figure, 4 table
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A Review of Default Mode Network Connectivity and Its Association With Social Cognition in Adolescents With Autism Spectrum Disorder and Early-Onset Psychosis
Recent studies have demonstrated substantial phenotypic overlap, notably social impairment, between autism spectrum disorder (ASD) and schizophrenia. However, the neural mechanisms underlying the pathogenesis of social impairments across these distinct neuropsychiatric disorders has not yet been fully examined. Most neuroimaging studies to date have focused on adults with these disorders, with little known about the neural underpinnings of social impairments in younger populations. Here, we present a narrative review of the literature available through April 2020 on imaging studies of adolescents with either ASD or early-onset psychosis (EOP), to better understand the shared and unique neural mechanisms of social difficulties across diagnosis from a developmental framework. We specifically focus on functional connectivity studies of the default mode network (DMN), as the most extensively studied brain network relevant to social cognition across both groups. Our review included 29 studies of DMN connectivity in adolescents with ASD (Mean age range = 11.2â21.6 years), and 14 studies in adolescents with EOP (Mean age range = 14.2â24.3 years). Of these, 15 of 29 studies in ASD adolescents found predominant underconnectivity when examining DMN connectivity. In contrast, findings were mixed in adolescents with EOP, with five of 14 studies reporting DMN underconnectivity, and an additional six of 14 studies reporting both under- and over-connectivity of the DMN. Specifically, intra-DMN networks were more frequently underconnected in ASD, but overconnected in EOP. On the other hand, inter-DMN connectivity patterns were mixed (both under- and over-connected) for each group, especially DMN connectivity with frontal, sensorimotor, and temporoparietal regions in ASD, and with frontal, temporal, subcortical, and cerebellar regions in EOP. Finally, disrupted DMN connectivity appeared to be associated with social impairments in both groups, less so with other features distinct to each condition, such as repetitive behaviors/restricted interests in ASD and hallucinations/delusions in EOP. Further studies on demographically well-matched groups of adolescents with each of these conditions are needed to systematically explore additional contributing factors in DMN connectivity patterns such as clinical heterogeneity, pubertal development, and medication effects that would better inform treatment targets and facilitate prediction of outcomes in the context of these developmental neuropsychiatric conditions
A Review of Default Mode Network Connectivity and Its Association With Social Cognition in Adolescents With Autism Spectrum Disorder and Early-Onset Psychosis
Recent studies have demonstrated substantial phenotypic overlap, notably social impairment, between autism spectrum disorder (ASD) and schizophrenia. However, the neural mechanisms underlying the pathogenesis of social impairments across these distinct neuropsychiatric disorders has not yet been fully examined. Most neuroimaging studies to date have focused on adults with these disorders, with little known about the neural underpinnings of social impairments in younger populations. Here, we present a narrative review of the literature available through April 2020 on imaging studies of adolescents with either ASD or early-onset psychosis (EOP), to better understand the shared and unique neural mechanisms of social difficulties across diagnosis from a developmental framework. We specifically focus on functional connectivity studies of the default mode network (DMN), as the most extensively studied brain network relevant to social cognition across both groups. Our review included 29 studies of DMN connectivity in adolescents with ASD (Mean age range = 11.2â21.6 years), and 14 studies in adolescents with EOP (Mean age range = 14.2â24.3 years). Of these, 15 of 29 studies in ASD adolescents found predominant underconnectivity when examining DMN connectivity. In contrast, findings were mixed in adolescents with EOP, with five of 14 studies reporting DMN underconnectivity, and an additional six of 14 studies reporting both under- and over-connectivity of the DMN. Specifically, intra-DMN networks were more frequently underconnected in ASD, but overconnected in EOP. On the other hand, inter-DMN connectivity patterns were mixed (both under- and over-connected) for each group, especially DMN connectivity with frontal, sensorimotor, and temporoparietal regions in ASD, and with frontal, temporal, subcortical, and cerebellar regions in EOP. Finally, disrupted DMN connectivity appeared to be associated with social impairments in both groups, less so with other features distinct to each condition, such as repetitive behaviors/restricted interests in ASD and hallucinations/delusions in EOP. Further studies on demographically well-matched groups of adolescents with each of these conditions are needed to systematically explore additional contributing factors in DMN connectivity patterns such as clinical heterogeneity, pubertal development, and medication effects that would better inform treatment targets and facilitate prediction of outcomes in the context of these developmental neuropsychiatric conditions
Psychological Approaches to Acute Pediatric Pain Management
Children endure numerous acute painful events, most of which occur within the medical arena. For instance, by the time a child reaches the age of 6, the child will have experienced approximately 30 immunization injections (Centers for Disease Control and Prevention, 2008). Grounded in the Gate Control Theory (Melzack & Wall, 1965), psychological methods of pain management have focused on anxiety and pain management via behavioral means. In addition, ample research has been devoted to how best to prepare children and their parents for upcoming painful or distress-provoking procedures (e.g., surgery, hospitalization, injection). This paper will review the preparation literature, which details how to inform and arm children and their parents for impending procedures and will highlight the psychological pain management literature which includes distraction, cognitive behavioral therapy, and additional promising interventions
Behavioral Approaches for Infant Pain Relief
Infants experience a host of painful medical procedures including heel sticks, venipuncture, and immunizations. Historically, little attention was given to infant pain management due to misconceived myths and beliefs about the experience and long-term effects of pain in infants. Recent data suggest that there are both short- and long-term negative repercussions associated with unmanaged infant pain. In response, a number of non-pharmacological approaches have been developed to provide infants with pain relief associated with medical events. This paper will review these behavioral approaches including positioning, parent training, distraction, sucrose, and skin-to-skin contact. Recommendations for best practices will be provided and future direction for infant pain management will be outlined
Nuclear Modification Factor for Charged Pions and Protons at Forward Rapidity in Central Au+Au Collisions at 200 GeV
We present spectra of charged pions and protons in 0-10% central Au+Au
collisions at GeV at mid-rapidity () and forward
pseudorapidity () measured with the BRAHMS experiment at RHIC. The
spectra are compared to spectra from p+p collisions at the same energy scaled
by the number of binary collisions. The resulting nuclear modification factors
for central Au+Au collisions at both and exhibit suppression
for charged pions but not for (anti-)protons at intermediate . The
ratios have been measured up to GeV/ at the two
rapidities and the results indicate that a significant fraction of the charged
hadrons produced at intermediate range are (anti-)protons at both
mid-rapidity and
Low Freeze-out Temperature and High Collective Velocities in Relativistic Heavy-Ion Collisions
On the basis of a nine-parameter expanding source model that includes special
relativity, quantum statistics, resonance decays, and freeze-out on a realistic
hypersurface in spacetime, we analyze in detail invariant pi+, pi-, K+, and K-
one-particle multiplicity distributions and pi+ and K+ two-particle
correlations in nearly central collisions of Si + Au at a laboratory bombarding
energy per nucleon of 14.6 GeV/c. By considering separately the one-particle
data and the correlation data, we find that the central baryon density, nuclear
temperature, transverse collective velocity, longitudinal collective velocity,
and source velocity are determined primarily by one-particle multiplicity
distributions and that the transverse radius, longitudinal proper time, width
in proper time, and pion incoherence fraction are determined primarily by
two-particle correlations. By considering separately the pion data and the kaon
data, we find that although the pion freeze-out occurs somewhat later than the
kaon freeze-out, the 99% confidence-level error bars associated with the two
freeze-outs overlap. These and other detailed studies confirm our earlier
conclusion based on the simultaneous consideration of the pion and kaon
one-particle and correlation data that the freeze-out temperature is less than
100 MeV and that both the longitudinal and transverse collective
velocities--which are anti-correlated with the temperature--are substantial. We
also discuss the flaws in several previous analyses that yielded a much higher
freeze-out temperature of approximately 140 MeV for both this reaction and
other reactions involving heavier projectiles and/or higher bombarding
energies.Comment: 14 pages. RevTeX 3.1. Submitted to Physical Review C. PostScript
version available at http://t2.lanl.gov/publications/publications.html or at
ftp://t2.lanl.gov/pub/publications/lf
Two-kaon correlations in central Pb + Pb collisions at 158 A GeV/c
Two-particle interferometry of positive kaons is studied in Pb + Pb
collisions at mean transverse momenta and 0.91 GeV/c. A
three-dimensional analysis was applied to the lower data, while a
two-dimensional analysis was used for the higher data. We find that the
source size parameters are consistent with the scaling curve observed in
pion correlation measurements in the same collisions, and that the duration
time of kaon emission is consistent with zero within the experimental
sensitivity.Comment: 4 pages incl. 1 table and 3 fig's; RevTeX; accepted for publication
in PR
Systematic Study of the Kaon to Pion Multiplicity Ratios in Heavy-Ion Collisions
We present a systematic study of the kaon to pion multiplicity ratios (K+/pi+
and K-/pi-) in heavy-ion collisions from AGS to RHIC energy using the
Relativistic Quantum Molecular Dynamics (RQMD) model. The model satisfactorily
describes the available experimental data on K+/pi+ and K-/pi-. Within the
model, we find that the strong increase of the ratios with the number of
participants is mainly due to hadronic rescattering of produced mesons with
ingoing baryons and their resonances. The enhancement of K/pi in heavy-ion
collisions with respect to elementary p+p interactions is larger at AGS energy
than SPS energy, and decreases smoothly with bombarding energy. The total
multiplicity ratios at RHIC energy are predicted by RQMD to be K+/pi+ = 0.19
and K-/pi- = 0.15.Comment: 10 pages, 8 figures, RevTeX style. A section is added to discuss
effects of rope formatio
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