Modelling spatial intensity for replicated inhomogeneous point patterns in brain imaging

Summary.  Pharmacological experiments in brain microscopy study patterns of cellular activ- ation in response to psychotropic drugs for connected neuroanatomic regions. A typical ex- perimental design produces replicated point patterns having highly complex spatial variability. Modelling this variability hierarchically can enhance the inference for comparing treatments. We propose a semiparametric formulation that combines the robustness of a nonparametric kernel method with the efficiency of likelihood-based parameter estimation. In the convenient framework of a generalized linear mixed model, we decompose pattern variation by kriging the intensities of a hierarchically heterogeneous spatial point process. This approximation entails discretizing the inhomogeneous Poisson likelihood by Voronoi tiling of augmented point patterns. The resulting intensity-weighted log-linear model accommodates spatial smoothing through a reduced rank penalized linear spline. To correct for anatomic distortion between subjects, we interpolate point locations via an isomorphic mapping so that smoothing occurs relative to common neuroanatomical atlas co-ordinates. We propose a criterion for choosing the degree and spatial locale of smoothing based on truncating the ordered set of smoothing covariates to minimize residual extra-dispersion. Additional spatial covariates, experimental design factors, hierarchical random effects and intensity functions are readily accommodated in the linear predictor, enabling comprehensive analyses of the salient properties underlying replicated point patterns. We illustrate our method through application to data from a novel study of drug effects on neuronal activation patterns in the brain of rats.     

Sexual Revictimization: Double Betrayal and the Risk Associated with Dissociative Amnesia

This study aimed to identify new treatment targets in order to develop more empirically informed initiatives to prevent sexual revictimization. A retrospective Web-based survey employing a mixed-methods design attracted a self-selecting sample of 481 community respondents, 183 of whom indicated a history of childhood sexual abuse. Seventy-four percent were females whose ages ranged from 16 to 69 years (mean = 31.2 years). Betrayal trauma referred to CSA committed by a trusted perpetrator (often caregivers). Disclosure experiences in childhood were reported though open-dialogue boxes. Double betrayal referred to high-betrayal trauma being combined with a negative response to a disclosure. This was associated with both higher incidences of prior psychogenic amnesia for CSA and sexual revictimization in later life. The findings have implications for educating the guardians of children about the prevalence and implications of CSA as well as the importance of early recognition and appropriate responding.     

Ethical publishing: the innocent author's guide to avoiding misconduct

Publication misconduct includes a range of unethical behaviours, such as plagiarism, breach of confidence and in appropriate authorship. The most egregious cases are easy to recognize and widely condemned, but the gradient between normal and unethical behaviour is often a gradual one. Clinicians and researchers should be aware of the full spectrum of publication misconduct and understand that some widely accepted practices may be unethical. This paper describes the various types of publication misconduct and offers guidance to authors, reviewers and journal editors about ways to detect and prevent them.     

Meta Analysis of Functional Neuroimaging Data via Bayesian Spatial Point Processes

As the discipline of functional neuroimaging grows there is an increasing interest in meta analysis of brain imaging studies. A typical neuroimaging meta analysis collects peak activation coordinates (foci) from several studies and identifies areas of consistent activation. Most imaging meta analysis methods only produce null hypothesis inferences and do not provide an interpretable fitted model. To overcome these limitations, we propose a Bayesian spatial hierarchical model using a marked independent cluster process. We model the foci as offspring of a latent study center process, and the study centers are in turn offspring of a latent population center process. The posterior intensity function of the population center process provides inference on the location of population centers, as well as the inter-study variability of foci about the population centers. We illustrate our model with a meta analysis consisting of 437 studies from 164 publications, show how two subpopulations of studies can be compared and assess our model via sensitivity analyses and simulation studies. Supplemental materials are available online.     

MODEL SELECTION FOR PENALIZED SPLINE SMOOTHING USING AKAIKE INFORMATION CRITERIA

Two different forms of Akaike's information criterion (AIC) are compared for selecting the smooth terms in penalized spline additive mixed models. The conditional AIC (cAIC) has been used traditionally as a criterion for both estimating penalty parameters and selecting covariates in smoothing, and is based on the conditional likelihood given the smooth mean and on the effective degrees of freedom for a model fit. By comparison, the marginal AIC (mAIC) is based on the marginal likelihood from the mixed‐model formulation of penalized splines which has recently become popular for estimating smoothing parameters. To the best of the authors' knowledge, the use of mAIC for selecting covariates for smoothing in additive models is new. In the competing models considered for selection, covariates may have a nonlinear effect on the response, with the possibility of group‐specific curves. Simulations are used to compare the performance of cAIC and mAIC in model selection settings that have correlated and hierarchical smooth terms. In moderately large samples, both formulations of AIC perform extremely well at detecting the function that generated the data. The mAIC does better for simple functions, whereas the cAIC is more sensitive to detecting a true model that has complex and hierarchical terms.     

Researching Sexual Revictimisation: Associated Ethical and Methodological Issues,and Possible Solutions

This paper has been inspired by the processes of preparing for ethical scrutiny and seeking ethical approval for a series of studies examining causal mechanisms that might facilitate sexual revictimisation. The focus here is on just four of the issues that arose in the context of the first study: a web‐based survey. One of the aims of the survey is to test whether victims of child sexual abuse who experienced a period of psychogenic or dissociative amnesia demonstrate an exaggerated risk for adolescent/adult sexual assault during this amnesic phase. That is, cases where survivors report ‘suddenly remembering’ in adulthood that they were abused as children, but state that prior to this ‘remembering’ they had no prior knowledge of their abuse. The study design is considered to be the first ethical issue. To enhance the methodological robustness a strategy has been employed to reduce the erroneous inclusion of currently amnesic participants in the non‐abused comparison group. Secondly, consideration is given to the likely harms and benefits that might be incurred or bestowed upon the participants. Thirdly, problems of both re‐traumatisation and vicarious traumatisation in relation to the researcher are contemplated and juxtaposed against the possibility of the facilitation of post‐traumatic growth and a personal shift towards wisdom and generativity. Finally, the survey title was originally criticised as negating ‘fully’ informed consent and a defence is therefore offered that ultimately gained ethical approval. It is hoped that these deliberations and insights may prove useful to others in planning their own research and ethics proposals.     

The Impact of Poverty on Children and Young People’s Use of Services

This article describes a qualitative study exploring the impact of poverty on children’s access to and use of services, which took a comparative approach to gather the views of children from more and less affluent households. Findings suggest affordability and related factors including limited mobility constrained service use for less affluent children, resulting in cumulative missed opportunities. However, extended family, friends and agencies facilitated service access, mitigating the impact of poverty on service use to some extent. Research implications include the importance of listening to and taking account of the views of children from lower income families in service planning.     

Genetic and environmental effects on sexual excitation and sexual inhibition in men

The Sexual Inhibition and Sexual Excitation Scales (SIS/SES) measure the propensity for sexual inhibition and excitation in men. According to the theoretical model underlying the SIS/SES, sexual response and associated behavior depend on dual control mechanisms in the brain involving the balance of excitatory and inhibitory systems which impinge on sexual response. Previous research with the SIS/SES has indicated one higher-order excitatory factor and two higher-order inhibitory factors affecting sexual response. The present study analyzed the item structure and the psychometric properties of the instrument in a population based sample of Finnish male twins (N = 1,289), and, including 37 out of 45 items of the original scales, estimated the heritability of and the environmental influences on the excitatory and inhibitory mechanisms. The twin correlations and the structural equation modeling suggested modest heritability for both inhibitory mechanisms. Sexual excitation, in contrast, was not influenced by genetic effects and similarities between twins for this mechanism seemed to be caused by the common environment of the twins.