How do health and biological age influence chronological age and sex differences in cognitive aging: Moderating, mediating, or both?

Much research on cognitive competence in normal older adults has documented age and sex differences. The authors used new cross-sectional data from the Victoria Longitudinal Study (VLS) (n = 386; age 61 to 95 years) to examine how health and biological age influence age and sex differences in cognitive aging. The authors found evidence for both moderating and mediating influences. Age differences were moderated by health status, such that the negative effects of age were most pronounced among participants of relatively better health. Sex differences were moderated by health and were more pronounced among participants reporting comparatively poorer health. Although health mediated a notable amount of age-related cognitive variation, BioAge mediated considerably more variance, even after statistical control for differences in health. A complex pattern emerged for the mediation of sex differences: Although BioAge accounted for sex-related variation in cognitive performance, health operated to suppress these differences. Overall, both health and BioAge predicted cognitive variation independently of chronological age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exploring gene–environment interactions: Socioregional moderation of alcohol use.

Examples of gene–environment interaction in human behavioral data are relatively rare; those that exist have used simple, dichotomous measures of the environment. The authors describe a model that allows for the specification of more continuous, more realistic variations in environments as moderators of genetic and environmental influences on behavior. Using data from a population-based Finnish twin study, the authors document strong moderating effects of socioregional environments on genetic and environmental influences on adolescent alcohol use, with nearly a five-fold difference in the magnitude of genetic effects between environmental extremes. The incorporation of specific environmental measures into genetically informative designs should prove to be a powerful method for better understanding the nature of gene–environment interaction and its contribution to the etiology of behavioral variation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in information-processing rate and amount: Implications for group differences in response latency.

Research on group differences in response latency often has as its goal the detection of Group ?×? Treatment interactions. However, accumulating evidence suggests that response latencies for different groups are often linearly related, leading to an increased likelihood of finding spurious overadditive interactions in which the slower group produces a larger treatment effect. The authors propose a rate-amount model that predicts linear relationships between individuals and that includes global processing parameters based on large-scale group differences in information processing. These global processing parameters may be used to linearly transform response latencies from different individuals to a common information-processing scale so that small-scale group differences in information processing may be isolated. The authors recommend linear regression and z-score transformations that may be used to augment traditional analyses of raw response latencies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nature-nurture reconceptualized in developmental perspective: a bioecological model

In response to Anastasi's (1958) long-standing challenge, the authors propose an empirically testable theoretical model that (a) goes beyond and qualifies the established behavioral genetics paradigm by allowing for nonadditive synergistic effects, direct measures of the environment, and mechanisms of organism-environment interaction, called proximal processes, through which genotypes are transformed into phenotypes; (b) hypothesizes that estimates of heritability (e.g., h2) increase markedly with the magnitude of proximal processes; (c) demonstrates that heritability measures the proportion of variation in individual differences attributable only to actualized genetic potential, with the degree of nonactualized potential remaining unknown; (d) proposes that, by enhancing proximal processes and environments, it is possible to increase the extent of actualized genetic potentials for developmental competence.     

Interval timing as an emergent learning property.

Interval timing in operant conditioning is the learned covariation of a temporal dependent measure such as wait time with a temporal independent variable such as fixed-interval duration. The dominant theories of interval timing all incorporate an explicit internal clock, or "pacemaker," despite its lack of independent evidence. The authors propose an alternative, pacemaker-free view that demonstrates that temporal discrimination can be explained by using only 2 assumptions: (a) variation and selection of responses through competition between reinforced behavior and all other, elicited, behaviors and (b) modulation of the strength of response competition by the memory for recent reinforcement. The model departs radically from existing timing models: It shows that temporal learning can emerge from a simple dynamic process that lacks a periodic time reference such as a pacemaker. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Placebo effects. Issues for clinical practice in psychiatry and medicine

Placebo effects are integral to everyday clinical practice; therefore, they should be well understood by all health care practitioners. Despite the rich literature on the topic, placebo effects receive only passing mention in major textbooks of psychiatry and medicine. The authors clarify the placebo construct and offer a selective review of its history, definitions, mechanisms, and relation to experimental methodology and statistics. Also considered are the concept of nocebo, variation in placebo response rates, and some economic and ethical problems with placebos in clinical trials. Directions are suggested for future research.     

Nature-nuture reconceptualized in developmental perspective: A bioecological model.

In response to A. Anastasi's (1958) long-standing challenge, the authors propose an empirically testable theoretical model that (1) goes beyond and qualifies the established behavioral genetics paradigm by allowing for nonadditive synergistic effects, direct measures of the environment, and mechanisms of organism–environment interaction, called proximal processes, through which genotypes are transformed into phenotypes; (2) hypothesizes that estimates of heritability (e.g., h–2) increase markedly with the magnitude of proximal processes; (3) demonstrates that heritability measures the proportion of variation in individual differences attributable only to actualized genetic potential, with the degree of nonactualized potential remaining unknown; and (4) proposes that, by enhancing proximal processes and environments, it is possible to increase the extent of actualized genetic potentials for developmental competence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extremely low birth weight infants have lower Fc gamma RIII (CD 16) plasma levels and their PMN produce less Fc gamma RIII compared to adults

The authors developed a new apparatus for extracting nitrogen or other inert gases from blood by flushing (sparging) the specimen with another gas. To investigate the utility of the new methodology, the apparatus was used in conjunction with a mass spectrometer to measure the blood N2 content of healthy normobaric, non-smoking, adult volunteers; the mean was found to be 11.7 microliters/ml +/- 0.9 microliter. This compares closely with values cited in the literature. The within-subject variation for repeat samples taken several weeks apart was significantly (P < 0.003) less than the variation between different subjects, suggesting that there may be true differences in N2 content between different individuals. These data must be considered preliminary, a larger study is needed to investigate population differences in detail. The advantages of the new method are discussed.     

Method-Specific Variance in the Implicit Association Test.

The Implicit Association Test (IAT; A. G. Greenwald, D. E. McGhee, & J. L. K. Schwartz, 1998) can be used to assess interindividual differences in the strength of associative links between representational structures such as attitude objects and evaluations. Four experiments are reported that explore the extent of method-specific variance in the IAT. The most important findings are that conventionally scored IAT effects contain reliable interindividual differences that are method specific but independent of the measures' content, and that IAT effects can be obtained in the absence of a preexisting association between the response categories. Several techniques to decrease the impact of method-specific variance are evaluated. The best results were obtained with the D measures recently proposed by A. G. Greenwald, B. A. Nosek, and M. R. Banaji (2003). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of sex and gender socialization in stress reactivity.

Individual health is determined by a myriad of factors. Interestingly, simply being male or female is one such factor that carries profound implications for one's well-being. Intriguing differences between men and women have been observed with respect to vulnerability to and prevalence of particular illnesses. The activity of the major stress hormone axis in humans, the hypothalamus-pituitary-adrenal axis, is directly and indirectly associated with the onset and propagation of these conditions. Previous studies have shown differences between men and women at the level of stress hormone regulation, suggesting that the metabolic effects of stress may be related to susceptibility for stress-related disease. While the majority of studies have suggested that biological differences are responsible, few have also considered the role of gender socialization. In this selective review, the authors summarize evidence on sex differences and highlight some recent results from endocrinological, developmental, and neuroimaging studies that suggest an important role of gender socialization on the metabolic effects of stress. Finally, a model is proposed that integrates these specific findings, highlighting gender socialization and stress responsivity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interaction of tannin with human salivary proline-rich proteins

Tannins are polyphenolic compounds, widely distributed in plant-based foods, which have harmful effects on animals including humans. Salivary proline-rich proteins (PRPs) may act as a defence against tannins by forming complexes with them and thereby preventing their interaction with other biological compounds and absorption from the intestinal canal. The aim here was to compare the ability of members of the family of human PRPs to form insoluble complexes with tannin and to assess the stability of such complexes under conditions similar to those in the alimentary tract. Basic PRPs (BPRPs), which have no other known biological functions, were very effective in forming insoluble complexes with both condensed tannin and tannic acid. Practically no tannin bound to acidic PRPs (APRPs) and glycosylated PRPs (GPRPs), suggesting that tannin in the diet would not affect their biological activities. There were only small differences in the tannin-precipitating ability of various BPRPs of different sizes or sequences, indicating that, although there is considerable phenotypic variation of PRPs, it is not likely to cause marked individual variation in tannin-binding ability. Tryptic digestion of an APRP led to a marked increase in tannin binding to the resulting proline-rich peptides, supporting observations in other studies that there may be an interaction between the proline-poor N-terminal and the proline-rich C-terminal regions in native APRPs, which inhibits the biological activities of the proteins. Deglycosylation of a GPRP also led to a dramatic increase in tannin-binding ability, showing that the carbohydrate side-chains prevent binding of tannin. Most of the condensed tannin-PRP complexes remained insoluble under conditions similar to those in the stomach and small intestine, supporting the proposal that PRPs act as a defence against tannin.     

Cumulative effects model: A response to Williams (1994).

The cumulative effects (CE) model explains free-operant choice by the ratio of total numbers of responses and reinforcements, a probability-like variable. B. A. Williams (see record 1995-08399-001) argues that the model is vulnerable to experiments that disprove melioration, a local probability model. The authors note critical differences between the nonlocal CE model and local probability models that allow the CE model to handle some data with which they are incompatible. All models are simplifications of reality; hence, a model's failures are as revealing as its successes. Williams suggests that simple models may need to be abandoned in favor of a "representational" account. The authors point out that representations must be both acquired and acted on. Acquisition requires processing of responses and reinforcers; action requires decision rules. Models are simply testable suggestions for what these rules and processes might be. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An attentional model of dimensional contrast.

In this article, the authors introduce a model of dimensional stimulus control designed to explain dimensional contrast effects. The model suggests that dimensional contrast is the result of the nonuniform allocation of limited attentional resources during discrimination training. Attention in the model is conceived as a gradient that extends throughout a spatial representation of stimuli. The authors examine the results of 5 experiments to assess the quality of fit of the model and its theoretical implications. Variations in training procedures, such as changing presentation probability of stimuli, changing the distribution of training stimuli, and changing the relative difficulty of discrimination, can all be accounted for by differences in the allocation of attentional resources. The good fit of the model indicates that attentional limitations may play an important role in stimulus control phenomena such as dimensional contrast. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Issues for covariance analysis of dichotomous and ordered categorical data from randomized clinical trials and non-parametric strategies for addressing them

Analysis of covariance is an effective method for addressing two considerations for randomized clinical trials. One is reduction of variance for estimates of treatment effects and thereby the production of narrower confidence intervals and more powerful statistical tests. The other is the clarification of the magnitude of treatment effects through adjustment of corresponding estimates for any random imbalances between the treatment groups with respect to the covariables. The statistical basis of covariance analysis can be either non-parametric, with reliance only on the randomization in the study design, or parametric through a statistical model for a postulated sampling process. For non-parametric methods, there are no formal assumptions for how a response variable is related to the covariables, but strong correlation between response and covariables is necessary for variance reduction. Computations for these methods are straightforward through the application of weighted least squares to fit linear models to the differences between treatment groups for the means of the response variable and the covariables jointly with a specification that has null values for the differences that correspond to the covariables. Moreover, such analysis is similarly applicable to dichotomous indicators, ranks or integers for ordered categories, and continuous measurements. Since non-parametric covariance analysis can have many forms, the ones which are planned for a clinical trial need careful specification in its protocol. A limitation of non-parametric analysis is that it does not directly address the magnitude of treatment effects within subgroups based on the covariables or the homogeneity of such effects. For this purpose, a statistical model is needed. When the response criterion is dichotomous or has ordered categories, such a model may have a non-linear nature which determines how covariance adjustment modifies results for treatment effects. Insight concerning such modifications can be gained through their evaluation relative to non-parametric counterparts. Such evaluation usually indicates that alternative ways to compare treatments for a response criterion with adjustment for a set of covariables mutually support the same conclusion about the strength of treatment effects. This robustness is noteworthy since the alternative methods for covariance analysis have substantially different rationales and assumptions. Since findings can differ in important ways across alternative choices for covariables (as opposed to methods for covariance adjustment), the critical consideration for studies with covariance analyses planned as the primary method for comparing treatments is the specification of the covariables in the protocol (or in an amendment or formal plan prior to any unmasking of the study.     

Structural and Orbital Conditions on Response of Large Space Structures

Effects of orbital and structural initial conditions, such as initial structural axial deformation, pitch (attitude) angle, and orbit altitude have been investigated on the subsequent orbital motion (time variation of orbit radius), attitude or pitch motion (time variation of pitch angle), and axial motion (time variation of axial length) of a large space structure in low earth orbit (LEO) and geosynchronous earth orbit (GEO). The space structure is assumed to be only axially flexible and executing a planar motion under the action of the earth's gravitational force. In LEO it is observed that the initial values of the axial deformation and pitch angle have appreciable effects on the structure's subsequent axial and attitude motions, whereas they have negligible effects on the structure's orbital motion. In GEO, the effects are found similar to those in LEO, except that the initial values of pitch angle have no effect on axial deformation. Furthermore, the investigation shows that the response of the space structure is greatly affected by the change in the orbit altitude. The study also indicates that flexibility of the structure has significant influence on its pitch librational motion.     

Detection of EEG abnormalities with feedback stimulation

A feedback method for testing the reactivity of the occipital-parietal EEG in selected brain-lesioned patients revealed abnormalities of (a) insufficient reactivity, (b) bilateral differences in reactivity, and (3) asynchrony. These abnormalities were more evident during feedback stimulation than in the baseline conditions. The utility of feedback method for detecting EEG abnormalities rests on the increased stability or decreased "noisy" variation in the EEG during feedback. The EEG becomes more predictable even to the "on-line" human observer. This makes it easier to detect aberrations or deviations from normal effects. Some effects can only be seen with feedback such as the bilateral differences which occur when the left side controls the feedback compared to when the right side controls it. The results show that feedback EEG is a useful tool in clinical research and indicate that a clinical diagnostic test could be developed with more research. However, the feedback EEG method is not yet a proven diagnostic technique.     

N-acetylcysteine does not influence the activity of endothelium-derived relaxing factor in vivo

Nitric oxide forms complexes with an array of biomolecular carriers that retain biological activity. This reactivity of nitric oxide in physiological systems has led to some dispute as to whether endothelium-derived relaxing factors nitric oxide or a closely related adduct thereof, such as a nitrosothiol. In vitro bioassays used to address this question are limited by the exclusion of biological thiols that are requisite for nitrosothiol formation. Thus, the purpose of this study was to obtain insight into the identity of endothelium-derived relaxing factor in vivo. We reasoned that if endothelium-derived relaxing factor in nitric oxide, infusion of physiological concentrations of thiol would potentiate its bioactivity by analogy with effects seen in vitro, whereas nitrosothiol would be resistant to such modulation. We used venous-occlusion plethysmography to study forearm blood flow in normal subjects. Methacholine (0.3 to 10 micrograms/min) and nitroglycerin (1 to 30 micrograms/min) were infused via the brachial artery to elicit endothelium-dependent and endothelium-independent vasodilation, respectively. Dose-response determinations were made for each drug before and after an intra-arterial infusion of the reduced thiol, N-acetylcysteine, at rates estimated to achieve a physiological concentration of 1 mmol/L. Methacholine increased forearm blood flow in a dose-dependent manner. Infusion of N-acetylcysteine did not change the sensitivity (ED50, 1.7 versus 1.7 micrograms/min, P = NS) or maximal response to methacholine. In contrast, thiol increased the sensitivity to nitroglycerin (ED50, 4.7 versus 2.8 micrograms/min, P < .01). Thus, conflicting with reports in vitro, thiol does not modulate endothelium-derived relaxing factor responses in vivo. These data indicate that sulfhydryl groups are not a limiting factor for endothelium-derived relaxing factor responses in forearm resistance vessels in normal humans and are in keeping with reports that nitrosothiol contributes to endothelium-derived relaxing factor bioactivity in plasma and vascular smooth muscle. Potentiation of the effects of nitroglycerin by N-acetylcysteine can be attributed to its enhanced biotransformation to an endothelium-derived relaxing factor equivalent, such as nitrosothiol. These observations support the notion of an equilibrium between nitric oxide and nitrosothiol in biological systems that may be influenced by redox state.     

The myth of perceptual defect: Sources and evidence.

A hypothesis of a perceptual defect in Black populations, suggested tentatively 20 yrs ago by L. E. Tyler (1956), was found to be still prevalent in the research literature. The hypothesis, its original data base, and more recent literature are examined. It was found that the hypothesis did not distinguish between the effects of race vs early experience on perceptual functioning. Reflecting this confusion, the authors argue that the original data base for the hypothesis was seriously flawed. Many studies assumed that the hypothesis could be demonstrated by lower scores on performance than on verbal subtests of IQ test batteries. The inadequacy of this assumption is discussed, and the use of IQ subtests to assess perceptual functioning is criticized. The need for measurement of response biases when attempting to assess group differences in perception is also stressed. An examination of the literature found few direct tests of ethnic differences in perception. Although some data tentatively suggest that there may be differences in visualization of spatial transformations, similar to the differences that have been found between the sexes, it is concluded that not enough data are available to make any general statement about ethnic differences in perception. (21/4 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A large-scale investigation of lateralization in cortical anatomy and word reading: Are there sex differences?

The authors report findings of a large-scale, multitask investigation of sex differences in both structural asymmetries and lateralization of word reading. Two hundred participants were tested in eight divided visual field lexical tasks, and each received a structural magnetic resonance imaging scan. The authors examined whether there was evidence for sex differences in overall measures of neuroanatomical and behavioral lateralization, in specific language tasks and brain regions, and in variation in asymmetry within and across tasks and brain regions. There was very little evidence for sex differences on any behavioral measure. The few indications of sex differences in the current report accounted for 2% or less of the individual variation in asymmetry and could not be replicated in independent subsamples. No sex differences were observed in the asymmetry of structures in Broca's and Wernicke's areas such as pars triangularis, pars opercularis, the planum temporale, planum parietale, or Heschl's gyrus. There were also no sex differences in the variability of neuroanatomical asymmetries within or between brain regions. However, a significant relationship between planum temporale and behavioral asymmetry was restricted to men. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delta Plots in the Study of Individual Differences: New Tools Reveal Response Inhibition Deficits in AD/HD That Are Eliminated by Methylphenidate Treatment.

The authors highlight the utility of distribution-analytical techniques in the study of individual differences and clinical disorders. Cognitive deficits associated with attention-deficit/hyperactivity disorder (AD/HD) were examined by using delta-plot analyses of performance data (reaction time and accuracy) obtained through the use of a prototypical conflict task, the Eriksen flanker task. In 20 children with AD/HD (compared with matched control participants), overall performance measures indicated a marginal performance deficit. Delta-plot analyses indicated that performance deficits associated with AD/HD involve response inhibition but not automatic response activation. In a within-subjects titration study, the response inhibition deficit was eliminated by methylphenidate treatment, but these effects were highly dose specific. The beneficial effect of methylphenidate was clarified further after correcting for inter-individual variation in sensitivity to medicine dosage. (PsycINFO Database Record (c) 2010 APA, all rights reserved)