Simulating three dimensional self-assembly of shape modified particles using magnetic dipolar forces

The feasibility of 3D self-assembly of milli-magnetic particles that interact via magnetic dipolar forces is investigated. Typically magnetic particles, such as isotropic spheres, self-organize in stable 2D configurations. By modifying the shape of the particles, 3D self-assembly may be enabled. The design of the particles and the experimental setup are presented. The magnetic configurations of simple particle arrangements are obtained via energy minimization in simulations. The simulations show that a 3D configuration can become energetically favourable over 2D configurations, if the shape of the particle is modified

The attentional blink modulates activity in the early visual cortex

The attentional blink (AB) documents a particularly strong case of visual attentional competition, in which subjects' ability to identify a second target (T2) is significantly impaired when it is presented with a short SOA after a first target (T1). We used functional magnetic resonance imaging to investigate the impact of the AB on visual activity in individually defined retinotopic representations of the target stimuli. Our results show reduction of neural response in V3 and marginally in V2 and V1, paralleling the behavioral AB effect. Reduction of visual activity was accompanied by reduced neural response in the inferior parietal cortex. This indicates that attentional competition modulates activity in higher-order parietal regions and the early visual cortex, providing a plausible neural basis of the behavioral AB effect

Humane risicobeoordeling in zicht : een inventarisatie van de mogelijkheden voor het optimaliseren van het gebruik van humane data bij de risicobeoordeling van chemische stoffen in de voeding

Het doel van deze studie was het identificeren van visies op het huidige risicobeoordelingsproces, het optimaliseren van het gebruik van humane data en de samenwerking tussen toxicologie en epidemiologie. Gegevens zijn verkregen middels 23 semigestructureerde interview

The effectiveness of Video-feedback Intervention to promote Positive Parenting for Foster Care (VIPP-FC)

Background: Foster children are at higher risk of the development of behavior and emotional problems, which can contribute to the development of insecure attachment bonds with their foster parents and (subsequently) to placement breakdown. Sensitive parenting might minimize the adverse effects of the behavior and emotional problems. Video-feedback Intervention to promote Positive Parenting and Sensitive Discipline in Foster Care (VIPP-FC) is an adaptation of the evidence-based Video-feedback Intervention to promote Positive Parenting and Sensitive Discipline (VIPP-SD) and aims at increasing sensitive parenting and the use of sensitive discipline strategies of foster parents. The current study is the first to examine the effectiveness of VIPP-FC. Methods: A randomized controlled trial is used with 60 foster parent-child dyads (intervention group n=30, control group n=30). The primary outcomes are parental sensitivity, parental disciplining, and parental attitudes towards parenting. Data about attachment (in)security, behavioral and emotional problems, neurobiological parameters, and possible confounders is additionally collected. Discussion: Examining the effectiveness of VIPP-FC contributes to the knowledge of evidence-based prevention and intervention programs needed in foster care practice

Estimation of conditional laws given an extreme component

Let $(X,Y)$ be a bivariate random vector. The estimation of a probability of the form $P(Y\leq y \mid X >t)$ is challenging when $t$ is large, and a fruitful approach consists in studying, if it exists, the limiting conditional distribution of the random vector $(X,Y)$, suitably normalized, given that $X$ is large. There already exists a wide literature on bivariate models for which this limiting distribution exists. In this paper, a statistical analysis of this problem is done. Estimators of the limiting distribution (which is assumed to exist) and the normalizing functions are provided, as well as an estimator of the conditional quantile function when the conditioning event is extreme. Consistency of the estimators is proved and a functional central limit theorem for the estimator of the limiting distribution is obtained. The small sample behavior of the estimator of the conditional quantile function is illustrated through simulations.Comment: 32 pages, 5 figur

Forward models demonstrate that repetition suppression is best modelled by local neural scaling

Inferring neural mechanisms from functional magnetic resonance imaging (fMRI) is challenging because the fMRI signal integrates over millions of neurons. One approach is to compare computational models that map neural activity to fMRI responses, to see which best predicts fMRI data. We use this approach to compare four possible neural mechanisms of fMRI adaptation to repeated stimuli (scaling, sharpening, repulsive shifting and attractive shifting), acting across three domains (global, local and remote). Six features of fMRI repetition effects are identified, both univariate and multivariate, from two independent fMRI experiments. After searching over parameter values, only the local scaling model can simultaneously fit all data features from both experiments. Thus fMRI stimulus repetition effects are best captured by down-scaling neuronal tuning curves in proportion to the difference between the stimulus and neuronal preference. These results emphasize the importance of formal modelling for bridging neuronal and fMRI levels of investigation.This work was supported by British Academy postdoctoral fellowship and a Marie Curie fellowship (753441) to A.A., a Cambridge University international scholarship and IDB merit scholarship award to H.A., and Medical Research Council programme grant (SUAG/010 RG91365) to R.N.H

Spatial band-pass filtering aids decoding musical genres from auditory cortex 7T fMRI

Spatial filtering strategies, combined with multivariate decoding analysis of BOLD images, have been used to investigate the nature of the neural signal underlying the discriminability of brain activity patterns evoked by sensory stimulation – primarily in the visual cortex. Previous research indicates that such signals are spatially broadband in nature, and are not primarily comprised of fine-grained activation patterns. However, it is unclear whether this is a general property of the BOLD signal, or whether it is specific to the details of employed analyses and stimuli. Here we applied an analysis strategy from a previous study on decoding visual orientation from V1 to publicly available, high-resolution 7T fMRI on the response BOLD response to musical genres in primary auditory cortex. The results show that the pattern of decoding accuracies with respect to different types and levels of spatial filtering is comparable to that obtained from V1, despite considerable differences in the respective cortical circuitry

Multivoxel Pattern Analysis Reveals Auditory Motion Information in MT+ of Both Congenitally Blind and Sighted Individuals

Cross-modal plasticity refers to the recruitment of cortical regions involved in the processing of one modality (e.g. vision) for processing other modalities (e.g. audition). The principles determining how and where cross-modal plasticity occurs remain poorly understood. Here, we investigate these principles by testing responses to auditory motion in visual motion area MT+ of congenitally blind and sighted individuals. Replicating previous reports, we find that MT+ as a whole shows a strong and selective responses to auditory motion in congenitally blind but not sighted individuals, suggesting that the emergence of this univariate response depends on experience. Importantly, however, multivoxel pattern analyses showed that MT+ contained information about different auditory motion conditions in both blind and sighted individuals. These results were specific to MT+ and not found in early visual cortex. Basic sensitivity to auditory motion in MT+ is thus experience-independent, which may be a basis for the region's strong cross-modal recruitment in congenital blindness

Predicting growth curves of early childhood externalizing problems: Differential susceptibility of children with difficult temperament

Using an accelerated longitudinal design, the development of externalizing problems from age 2 to 5 years was investigated in relation to maternal psychopathology, maternal parenting, gender, child temperament, and the presence of siblings. The sample consisted of 150 children selected at age 2-3 years for having high levels of externalizing problems. Parenting was measured using observational methods, and maternal reports were used for the other variables. Overall, mean levels of externalizing problems decreased over time, and higher initial levels (intercept) were related to a stronger decrease (negative slope) in externalizing problems. Results showed that higher levels of maternal psychopathology were related to less decrease in early childhood externalizing problems. Parental sensitive behavior predicted a stronger decrease in externalizing problems, but only for children with difficult temperaments. A stronger decrease of externalizing problems in children with older siblings also pertained only to children with difficult temperaments. Thus, temperamentally difficult children appear to be more susceptible to environmental influences on the development of externalizing behaviors. Our results indicate that the role of siblings in early childhood externalizing problems deserves more research attention, and that intervention efforts need to take into account temperamental differences in children's susceptibility to environmental influences. © 2009 Springer Science+Business Media, LLC