2,227 research outputs found
Simulation of cholinergic and noradrenergic modulation of behavior in uncertain environments
Attention is a complex neurobiological process that involves rapidly and flexibly balancing sensory input and goal-directed predictions in response to environmental changes. The cholinergic and noradrenergic systems, which have been proposed to respond to expected and unexpected environmental uncertainty, respectively, play an important role in attention by differentially modulating activity in a multitude of cortical targets. Here we develop a model of an attention task that involves expected and unexpected uncertainty. The cholinergic and noradrenergic systems track this uncertainty and, in turn, influence cortical processing in five different, experimentally verified ways: (1) nicotinic enhancement of thalamocortical input, (2) muscarinic regulation of corticocortical feedback, (3) noradrenergic mediation of a network reset, (4) locus coeruleus (LC) activation of the basal forebrain (BF), and (5) cholinergic and noradrenergic balance between sensory input and frontal cortex predictions. Our results shed light on how the noradrenergic and cholinergic systems interact with each other and a distributed set of neural areas, and how this could lead to behavioral adaptation in the face of uncertainty
Drug Adverse Event Detection in Health Plan Data Using the Gamma Poisson Shrinker and Comparison to the Tree-based Scan Statistic
Background: Drug adverse event (AE) signal detection using the Gamma Poisson Shrinker (GPS) is commonly applied in spontaneous reporting. AE signal detection using large observational health plan databases can expand medication safety surveillance. Methods: Using data from nine health plans, we conducted a pilot study to evaluate the implementation and findings of the GPS approach for two antifungal drugs, terbinafine and itraconazole, and two diabetes drugs, pioglitazone and rosiglitazone. We evaluated 1676 diagnosis codes grouped into 183 different clinical concepts and four levels of granularity. Several signaling thresholds were assessed. GPS results were compared to findings from a companion study using the identical analytic dataset but an alternative statistical method—the tree-based scan statistic (TreeScan). Results: We identified 71 statistical signals across two signaling thresholds and two methods, including closely-related signals of overlapping diagnosis definitions. Initial review found that most signals represented known adverse drug reactions or confounding. About 31% of signals met the highest signaling threshold. Conclusions: The GPS method was successfully applied to observational health plan data in a distributed data environment as a drug safety data mining method. There was substantial concordance between the GPS and TreeScan approaches. Key method implementation decisions relate to defining exposures and outcomes and informed choice of signaling thresholds
Supergoop Dynamics
We initiate a systematic study of the dynamics of multi-particle systems with
supersymmetric Van der Waals and electron-monopole type interactions. The
static interaction allows a complex continuum of ground state configurations,
while the Lorentz interaction tends to counteract this configurational fluidity
by magnetic trapping, thus producing an exotic low temperature phase of matter
aptly named supergoop. Such systems arise naturally in gauge
theories as monopole-dyon mixtures, and in string theory as collections of
particles or black holes obtained by wrapping D-branes on internal space
cycles. After discussing the general system and its relation to quiver quantum
mechanics, we focus on the case of three particles. We give an exhaustive
enumeration of the classical and quantum ground states of a probe in an
arbitrary background with two fixed centers. We uncover a hidden conserved
charge and show that the dynamics of the probe is classically integrable. In
contrast, the dynamics of one heavy and two light particles moving on a line
shows a nontrivial transition to chaos, which we exhibit by studying the
Poincar\'e sections. Finally we explore the complex dynamics of a probe
particle in a background with a large number of centers, observing hints of
ergodicity breaking. We conclude by discussing possible implications in a
holographic context.Comment: 35 pages,11 figures. v2: updated references to include a previous
proof of classical integrability, exchanged a figure for a prettier versio
KL Estimation of the Power Spectrum Parameters from the Angular Distribution of Galaxies in Early SDSS Data
We present measurements of parameters of the 3-dimensional power spectrum of
galaxy clustering from 222 square degrees of early imaging data in the Sloan
Digital Sky Survey. The projected galaxy distribution on the sky is expanded
over a set of Karhunen-Loeve eigenfunctions, which optimize the signal-to-noise
ratio in our analysis. A maximum likelihood analysis is used to estimate
parameters that set the shape and amplitude of the 3-dimensional power
spectrum. Our best estimates are Gamma=0.188 +/- 0.04 and sigma_8L = 0.915 +/-
0.06 (statistical errors only), for a flat Universe with a cosmological
constant. We demonstrate that our measurements contain signal from scales at or
beyond the peak of the 3D power spectrum. We discuss how the results scale with
systematic uncertainties, like the radial selection function. We find that the
central values satisfy the analytically estimated scaling relation. We have
also explored the effects of evolutionary corrections, various truncations of
the KL basis, seeing, sample size and limiting magnitude. We find that the
impact of most of these uncertainties stay within the 2-sigma uncertainties of
our fiducial result.Comment: Fig 1 postscript problem correcte
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