Neuropathology of Rett syndrome

Rett Syndrome is unlike any other pediatric neurologic disease, and its clinical-pathologic correlation can not be defined with standard histology techniques. Based on hypotheses suggested by careful clinical observations, the nervous system of the Rett child has been explored utilizing morphometry, golgi preparations, computerized tomography, magnetic resonance imaging, chemistry, immunocytochemistry, autoradiography, and molecular biologic techniques. From these many perspectives we conclude that Rett syndrome is not a typical degenerative disorder, storage disorder, nor the result of gross malformation, infectious or neoplastic processes. There remain regions of the brain that have not been studied in detail but the available data suggest that the neuropathology of Rett syndrome can be summarized as follows: the Rett brain is small for the age and the height of the patient; it does not become progressively smaller over three to four decades; it has small dendritic trees in pyramidal neurons of layers III and V in selected lobes (frontal, motor, and temporal); it has small neurons with an increased neuronal packing density; it has an immature expression of microtubular protein-2 and cyclooxygenase; it exhibits a changing pattern of neurotransmitter receptors with an apparent reduction in many neurotransmitters, possibly contributing to some symptomatology. A mutation in Mecp2 causes this unique disorder of brain development. Neuronal mosaicism for normal and mutated Mecp2 produces a consistent phenotype in the classic female patient and a small brain with some preserved islands of function, but with an inability to support hand use and speech. This paper summarizes our current observations about neuropathology of Rett syndrome. MRDD Research Reviews 2002;8:72-76.     

Infants and toddlers discriminate amount: are they measuring?

Four experiments that show an early ability to encode and retain information about extent are presented. We found that infants discriminate between the heights of dowels in a habituation task. We also found that toddlers discriminate between heights on a choice task in which a target dowel is presented and removed and they then choose between the target and a foil. Until 4 years of age, however, discrimination occurs only in the presence of a perceptually salient standard. Adults do not require a perceptually present standard; they can assess extent across temporal or spatial gaps by imposing a standard (measure). The present findings indicate that infants and toddlers do not possess an adult ability to establish extent, but that they do possess a skill that provides a start point for this important intellectual achievement.     

Reduction Invariance and Prelec's Weighting Functions

Within the framework of separable utility theory, a condition, called reduction invariance, is shown to be equivalent to the 2-parameter family of weighting functions that Prelec (1998) derived from the condition called compound invariance. Reduction invariance, which is a variant on the reduction of compound gambles, is appreciably simpler and more easily testable than compound invariance, and a simpler proof is provided. Both conditions are generalized leading to more general weighting functions that include, as special cases, the families of functions that Prelec called exponential-power and hyperbolic logarithm and that he derived from two other invariance principles. However, of these various families, only Prelec's compound-invariance family includes, as a special case, the power function, which arises from the simplest probabilistic assumption of reduction of compound gambles. Copyright 2001 Academic Press.     

Parents who report using illicit drugs: findings and implications from the DRUGNET study

In recent years, a national discussion has emerged concerning what parents should tell their children about their own past drug use. DRUGNET is an ongoing, on-line survey of successful, healthy, adults who occasionally use illicit drugs. This paper reviews data from a subset of this survey, namely, those respondents who were parents with self-reported use of at least one illicit drug. The sample (n = 325) was predominantly white men who reported having above average education and household incomes. Their mental health as measured by the General Well-being Schedule was similar to the national norm. Respondents reported using drugs to manage parental stress and expressed concerns over how to communicate with their children and legal risks related to their own drug use. The limitations and the implications of these data are discussed.     

From the interpersonal to the international: understanding commitment to the "war on terror"

Applying constructs from the investment model used traditionally to understand interpersonal commitment, the present investigation seeks to elucidate social cognitive antecedents of commitment to the war on terror waged by the United States. In Study 1, satisfaction with, investments in, and alternatives to the war on terror predict levels of commitment to the war beyond several important control variables. In Study 2, levels of satisfaction with, investments in, and alternatives to the war are experimentally manipulated. The highest levels of commitment to the war are observed among participants exposed to a high satisfaction, high investment, and low alternatives scenario, and the lowest levels are among those exposed to a low satisfaction, low investment, and high alternatives scenario. These results support broadening the targets of commitment normally considered within the context of the investment model and suggest applying relational models to understanding broader societal concerns.     

Potential moral stigma and reactions to sexually transmitted diseases: evidence for a disjunction fallacy

Five experiments demonstrate how potential moral stigma leads people to underplay their susceptibility to sexually transmitted diseases (STDs) and dampens their interest in getting tested. After adding unprotected sex to a list of otherwise innocuous possible vectors for a disease, the authors found that infected people were perceived to be less moral (Experiment 1a), and individuals believed that if they had the disease, others would see them as less moral too (Experiment 1b). Adding this stigmatized vector also reduced reported testing intentions (Experiment 2) and perceived risk of exposure (Experiment 3)--a disjunction fallacy because adding a potential cause reduced estimated likelihood, in violation of basic probability rules. Finally, the authors replicated the effect in a computer virus analog (Experiment 4) and showed that it did not result from simply knowing that one has not engaged in the stigmatized behavior. Results suggest that avoidance of potential stigma can have dramatic health consequences, both for an individual's health decision and for health policy.     

Taxometric analysis of the antisocial features scale of the personality assessment inventory in federal prison inmates

The Antisocial Features (ANT) scale of the Personality Assessment Inventory (PAI) was subjected to taxometric analysis in a group of 2,135 federal prison inmates. Scores on the three ANT subscales-Antisocial Behaviors (ANT-A), Egocentricity (ANT-E), and Stimulus Seeking (ANT-S)-served as indicators in this study and were evaluated using the following taxometric procedures: mean above minus below a cut (MAMBAC), maximum eigenvalue (MAXEIG), and latent mode factor analysis (L-Mode). Objective and subjective evaluation of the results revealed consistent support for a dimensional interpretation of latent structure across the di ferent taxometric procedures as well as across gender, race, and security level. As a dimensional construct, antisocial personality disorder arranges respondents along one or more quantitative dimensions (degree of antisociality), rather than assigning them to qualitatively distinct categories (antisocial or not antisocial).     

Bilateral entorhinal cortex lesions impair acquisition of delayed spatial alternation in rats

Entorhinal cortex lesions induce significant reorganization of several homotypic and heterotypic inputs to the hippocampus. This investigation determined whether surviving heterotypic inputs after bilateral entorhinal lesions would support the acquisition of a learned alternation task. Rats with entorhinal lesions or sham operations were trained to acquire a spatial alternation task. Although the sham-operated rats acquired the task within about 3 weeks postsurgery, rats with bilateral entorhinal lesions failed to learn the task after 12 consecutive weeks of training despite heterotypic sprouting of the cholinergic septodentate pathway and the expansion of the commissural/associational fiber plexus within the dentate gyrus. Thus, heterotypic sprouting failed to ameliorate significantly the effects of bilateral entorhinal lesions. Rather, entorhinal lesions produced a persistent impairment of spatial memory, characterized by a mixture of random error production and perseverative responding.     

Parental influence on youth propensity to join the military

The purpose of this research was to apply the Theory of Planned Behavior (TPB) in a model of youths’ career choice intentions and parents’ recommendation intentions. Specifically, a TPB model was developed for youth-parent dyads and tested with SEM to examine parental influence on youth intentions as well as behavior. Results indicated that a modified TPB model is useful for describing how youth and parent beliefs translate into enlistment intentions and pre-enlistment behavior. The strongest impact parents appeared to have on their children was through efficacy beliefs, followed by the link between parents’ attitudes and youths’ normative beliefs. Implications for recruitment and outreach efforts are discussed.