Coordinated optimization of visual cortical maps (II) Numerical studies

It is an attractive hypothesis that the spatial structure of visual cortical architecture can be explained by the coordinated optimization of multiple visual cortical maps representing orientation preference (OP), ocular dominance (OD), spatial frequency, or direction preference. In part (I) of this study we defined a class of analytically tractable coordinated optimization models and solved representative examples in which a spatially complex organization of the orientation preference map is induced by inter-map interactions. We found that attractor solutions near symmetry breaking threshold predict a highly ordered map layout and require a substantial OD bias for OP pinwheel stabilization. Here we examine in numerical simulations whether such models exhibit biologically more realistic spatially irregular solutions at a finite distance from threshold and when transients towards attractor states are considered. We also examine whether model behavior qualitatively changes when the spatial periodicities of the two maps are detuned and when considering more than 2 feature dimensions. Our numerical results support the view that neither minimal energy states nor intermediate transient states of our coordinated optimization models successfully explain the spatially irregular architecture of the visual cortex. We discuss several alternative scenarios and additional factors that may improve the agreement between model solutions and biological observations.Comment: 55 pages, 11 figures. arXiv admin note: substantial text overlap with arXiv:1102.335

Mindfulness in schools: a health promotion approach to improving adolescent mental health.

Between 10 and 20% of adolescents worldwide experience a mental health problem within a given 12-month period. Mental health problems impact on an adolescent’s potential to live a fulfilling and productive life and lead to challenges such as stigma, isolation and discrimination. To address this need, in recent years, there has been growing interest into broad-based school-integrated health promotion interventions that seek to build resilience and augment protective factors in adolescents. Mindfulness-based interventions (MBIs) reflect one such approach that have been administered to adolescent populations in both resilience building and treatment contexts. This paper discusses the utility of school-based MBIs as an adolescent health promotion approach and makes recommendations for intervention design, delivery and evaluation. Emerging evidence indicates that school-integrated MBIs may be a cost-effective means of not only meeting government objectives relating to adolescent mental health, but also for improving the wellbeing of teachers and parents. Furthermore, there is growing evidence indicating that mindfulness can elicit improvements in student learning performance and general classroom behaviour. However, notwithstanding these beneficial properties, there remains a need to conduct large-scale empirical investigations that seek to evaluate the effectiveness of school-integrated MBIs at a regional or national level. A further challenge is the need to ensure that mindfulness instructors are able to impart to adolescents an experiential understanding of this ancient contemplative technique.N

Molecular Mechanics of the α-Actinin Rod Domain: Bending, Torsional, and Extensional Behavior

α-Actinin is an actin crosslinking molecule that can serve as a scaffold and maintain dynamic actin filament networks. As a crosslinker in the stressed cytoskeleton, α-actinin can retain conformation, function, and strength. α-Actinin has an actin binding domain and a calmodulin homology domain separated by a long rod domain. Using molecular dynamics and normal mode analysis, we suggest that the α-actinin rod domain has flexible terminal regions which can twist and extend under mechanical stress, yet has a highly rigid interior region stabilized by aromatic packing within each spectrin repeat, by electrostatic interactions between the spectrin repeats, and by strong salt bridges between its two anti-parallel monomers. By exploring the natural vibrations of the α-actinin rod domain and by conducting bending molecular dynamics simulations we also predict that bending of the rod domain is possible with minimal force. We introduce computational methods for analyzing the torsional strain of molecules using rotating constraints. Molecular dynamics extension of the α-actinin rod is also performed, demonstrating transduction of the unfolding forces across salt bridges to the associated monomer of the α-actinin rod domain

The history of attention deficit hyperactivity disorder

The contemporary concept of attention deficit hyperactivity disorder (ADHD) as defined in the DSM-IV-TR (American Psychiatric Association 2000) is relatively new. Excessive hyperactive, inattentive, and impulsive children have been described in the literature since the nineteenth century. Some of the early depictions and etiological theories of hyperactivity were similar to current descriptions of ADHD. Detailed studies of the behavior of hyperactive children and increasing knowledge of brain function have changed the concepts of the fundamental behavioral and neuropathological deficits underlying the disorder. This article presents an overview of the conceptual history of modern-day ADHD