Bayesian inference in probabilistic risk assessment—The current state of the art

Markov chain Monte Carlo (MCMC) approaches to sampling directly from the joint posterior distribution of aleatory model parameters have led to tremendous advances in Bayesian inference capability in a wide variety of fields, including probabilistic risk analysis. The advent of freely available software coupled with inexpensive computing power has catalyzed this advance. This paper examines where the risk assessment community is with respect to implementing modern computational-based Bayesian approaches to inference. Through a series of examples in different topical areas, it introduces salient concepts and illustrates the practical application of Bayesian inference via MCMC sampling to a variety of important problems.     

Polybrominated diphenyl ethers (PBDEs) in Lake Michigan forage fish

Polybrominated diphenyl ethers (PBDEs) were analyzed in 88 forage fish samples collected from Lake Michigan in 1995 and in 2002/2003. Lipid-normalized total PBDE concentrations ranged from 149 to 1094 ng/g. Total PBDEs in alewife and deepwater sculpin did not change significantly from 1995 to 2002/2003, while the levels in bloater chub and the slimy sculpin decreased. BDE-47 was the most abundant congener in the fish. All of the forage fish were depleted in BDE-99 relative to what would be expected based on the congener composition of the commercial formulation in use. The deepwater sculpins were particularly lacking in BDE-99. Changes in the food web brought about by the dramatic decline of Diporeia abundance (due to the invasion of zebra and quagga mussels) may have affected the levels of PBDEs in some of the forage fish.     

Wavefront-based models for inverse electrocardiography

We introduce two wavefront-based methods for the inverse problem of electrocardiography, which we term wavefront-based curve reconstruction (WBCR) and wavefront-based potential reconstruction (WBPR). In the WBCR approach, the epicardial activation wavefront is modeled as a curve evolving on the heart surface, with the evolution governed by factors derived phenomenologically from prior measured data. The body surface potential/wavefront relationship is modeled via an intermediate mapping of wavefront to epicardial potentials, again derived phenomenologically. In the WBPR approach, we iteratively construct an estimate of epicardial potentials from an estimated wavefront curve according to a simplified model and use it as an initial solution in a Tikhonov regularization scheme. Initial simulation results using measured canine epicardial data show considerable improvement in reconstructing activation wavefronts and epicardial potentials with respect to standard Tikhonov solutions. In particular the WBCR method accurately finds the anisotropic propagation early after epicardial pacing, and the WBPR method finds the wavefront (regions of sharp gradient of the potential) both accurately and with minimal smoothing.     

Mediators of a brief hypnosis intervention to control side effects in breast surgery patients: Response expectancies and emotional distress.

Objective: The present study was designed to test the hypotheses that response expectancies and emotional distress mediate the effects of an empirically validated presurgical hypnosis intervention on postsurgical side effects (i.e., pain, nausea, and fatigue). Method: Women (n = 200) undergoing breast-conserving surgery (mean age = 48.50 years; 63% White, 15% Hispanic, 13% African American, and 9% other) were randomized to a hypnosis or to an attention control group. Prior to surgery, patients completed assessments of hypothesized mediators (response expectancies and emotional distress), and following surgery, patients completed assessments of outcome variables (pain, nausea, and fatigue). Results: Structural equation modeling revealed the following: (a) Hypnotic effects on postsurgical pain were partially mediated by pain expectancy (p p = .12); (b) hypnotic effects on postsurgical nausea were partially mediated by presurgical distress (p = .02) but not by nausea expectancy (p = .10); and (c) hypnotic effects on postsurgical fatigue were partially mediated by both fatigue expectancy (p = .0001) and presurgical distress (p = .02). Conclusions: The results demonstrate the mediational roles of response expectancies and emotional distress in clinical benefits associated with a hypnotic intervention for breast cancer surgical patients. More broadly, the results improve understanding of the underlying mechanisms responsible for hypnotic phenomena and suggest that future hypnotic interventions target patient expectancies and distress to improve postsurgical recovery. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optimal linear inverse solution with multiple priors in diffuse optical tomography

A general framework for incorporating single and multiple priors in diffuse optical tomography is described. We explore the use of this framework for simultaneously utilizing spatial and spectral priors in the context of imaging breast cancer. The utilization of magnetic resonance images of water and lipid content as a statistical spatial prior for the diffuse optical image reconstructions is also discussed. Simulations are performed to demonstrate the significant improvement in image quality afforded by combining spatial and spectral priors.     

Selection of a target for defensive projection.

This hypothesis was tested and supported (p     

Radial localization in the aged.

Elderly subjects were 41% less accurate than young subjects in localizing a point in the frontal plane. The decline could be ascribed neither to an age difference in image formation or skill acquisition nor to a difference in motivational level or trace retention. Evidently the "ambient" or "transient" visual system is compromised at an elementary level. Reasons why this deficit may not be compounded at more complex levels of spatial processing are suggested. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relation of depression and help-seeking history to attitudes toward seeking professional psychological help.

We investigated the relation of help-seeking history, sex, and depression to college students' attitudes, beliefs, and intentions about obtaining professional psychological help. College students completed questionnaires that included the Beck Depression Inventory (Beck, Ward, Mendelson, Mock, & Erbaugh, 1961), an inquiry about help-seeking history, and an attitude scale constructed according to the method posited in the theory of reasoned action (Ajzen & Fishbein, 1980). Of these 429, 126 who represented extremes of the depression continuum were selected as subjects for data analyses. Though sex differences were not found, results indicated that the experience of having sought help is positively related to how one feels about seeking help and that the experience of depression, regardless of help-seeking history, is also related to more positive attitudes, beliefs, and intentions. Implications for educative interventions are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)