Mechanisms of perceptual learning of depth discrimination in random dot stereograms.

Perceptual learning is a training induced improvement in performance. Mechanisms underlying the perceptual learning of depth discrimination in dynamic random dot stereograms were examined by assessing stereothresholds as a function of decorrelation. The inflection point of the decorrelation function was defined as the level of decorrelation corresponding to 1.4 times the threshold when decorrelation is 0%. In general, stereothresholds increased with increasing decorrelation. Following training, stereothresholds and standard errors of measurement decreased systematically for all tested decorrelation values. Post training decorrelation functions were reduced by a multiplicative constant (approximately 5), exhibiting changes in stereothresholds without changes in the inflection points. Disparity energy model simulations indicate that a post-training reduction in neuronal noise can sufficiently account for the perceptual learning effects. In two subjects, learning effects were retained over a period of six months, which may have application for training stereo deficient subjects.

Neural analogs of associative learning in {\it Aplysia\/}: Experimental and theoretical approaches

A change in synaptic strength arising from the activation of two neuronal pathways at approximately the same time is a form of associative plasticity and may underlie classical conditioning. Previously, a cellular analog of a classical conditioning protocol has been demonstrated to produce short-term associative plasticity at the connections between sensory and motor neurons in Aplysia. A similar training protocol produced long-term (24 hour) enhancement of excitatory postsynaptic potentials (EPSPs). EPSPs produced by sensory neurons in which activity was paired with a reinforcing stimulus were significantly larger than unpaired controls 24 hours after training. To examined whether the associative plasticity observed at these synapses may be involved in higher-order forms of classical conditioning, a neural analog of contingency was developed. In addition, computer simulations were used to analyze whether the associative plasticity observed in Aplysia could, in theory, account for second-order conditioning and blocking. ^

Survey of VFC provider knowledge of catch-up regimens and contraindications to vaccination in Houston, Texas

In 2004, Houston had one of the lowest childhood immunization levels among major metropolitan cities in the United States at 65% for the 4:3:1:3:3 vaccination series. Delays in the receipt of scheduled vaccinations may be related to missed opportunities due to health care provider lack of knowledge about catch-up regimens and contraindications for pediatric vaccination. The objectives of this study are to identify, measure, and report on VFC provider-practice characteristics, knowledge of catch-up regimens and contraindications, and use of Reminder recall (R/R) and moved or gone elsewhere (MOGE) practices among providers with high (>80%) and low (<70%) immunization coverage among 19-35 month old children. The sampling frame consists of 187 Vaccines for Children (VFC) providers with 2004 clinic assessment software application (CASA) scores. Data were collected by personal interview with each participating practice provider. Only ten VFC providers were successful at maximizing vaccinations for every vignette and no provider administered the maximum possible number of vaccinations at visit 2 for all six vignettes. Both coverage groups administered polio conjugate vaccine (PCV), haemophilus influenza type b (Hib), and diphtheria, tetanus and acellular pertussis (DTaP) most frequently and omitted most frequently varicella zoster vaccine (VZV) and measles, mumps, and rubella (MMR) vaccine. ^

Knowledge of exercise recommendations and energy intake from foods and beverages in relation to exercise behaviors within two Hispanic border communities

This research is a secondary analysis of the Qué Sabrosa Vida population-based cross-sectional study of two predominately Mexican American communities located along the Texas-Mexico border in 2000. There were two aims for this research. The first was to determine the relationship between knowledge of exercise and water recommendations, and exercise behavior and water consumption. The second was to determine the relationship between exercise behavior and percentage of energy consumption from beverages. Chi-square analysis revealed the majority of both populations had adequate knowledge about water and exercise recommendations, although significant percentages of the populations (>40%) did not consume water or exercise in adequate amounts. Knowledge was found to be a component of both behaviors, as it was more prevalent in the adults who exercised and consumed water in adequate amounts. Analysis of variance revealed no significant difference between overall beverage calorie percentage and exercise level (all p-values > 0.05); both regions and genders reported ∼18% of total caloric intake from beverages. There was no disproportionate influence of beverage calories on total caloric intake, after controlling for water consumption and independent of exercise behavior. These findings suggest that overall caloric intake, from both foods and beverages, may be the most influential factor to the energy imbalance contributing to the obesity crisis in these Hispanic border populations. ^

Contraceptive attitudes and knowledge of female adolescents

Despite the recent decline in adolescent pregnancy rates, adolescent pregnancy continues to be a significant public health issue in the United States. The United States consistently reports the highest rate of adolescent pregnancy among developed countries. Adolescent mothers are more likely to have multiple pregnancies, to access welfare and other social services, and to be unmarried. Teen mothers are less likely to complete high school, enter college, and typically command much less earning power throughout their lifetime as compared to women who delay childbirth until later. Moreover, the United States spends approximately $9.1 billion annually on teen pregnancies. ^ Additionally disconcerting is recent data which demonstrates that the decline in teen pregnancy rates is leveling off and that the rate of adolescent pregnancy has increased for the first time since 1993. Contraceptive use is a key component to the prevention of adolescent pregnancy. Contraceptive nonuse and failure result in unintended pregnancies among adolescents. This review sought to assess the levels of knowledge and attitudes toward contraception among adolescent females.^ Levels of knowledge of contraception among adolescents are tolerable; however, there is substantial room for improvement. Misperceptions about the side effects and mechanisms of action of contraception are pervasive among this population. Adolescents who have low levels of knowledge regarding contraception tend to discontinue usage or use inconsistently. Attitudes toward contraception are greatly influenced by levels of knowledge. As a result, adolescents tend to develop more positive attitudes as misperceptions are abated. Moreover, clear disparities persist among adolescents with minority and young adolescents being at increased risk of pregnancy, poor contraceptive use, and insufficient knowledge about contraception.^ Understanding the level of knowledge of and attitudes toward contraceptives among adolescents is essential to the development of effective pregnancy prevention programs. In order to effectively reduce adolescent pregnancy, prevention initiatives must target the vulnerable populations and incorporate the necessary cultural components.^

US medical students' knowledge of obstetric fistula in developing countries

Obstetric fistula is a devastating child birth injury affecting millions of women worldwide. This paper explores the knowledge and understanding of medical students at the University of Texas Health Science Center at San Antonio regarding this global public health issue. Obstetric fistula has been eradicated in most industrialized nations, and has therefore faded from view of many modern medical organizations. The United Nations Population Fund has launched a “Campaign to End Fistula” in an attempt to bring global awareness to this preventable and treatable condition. Based on a survey administered to medical students at UTHSCSA, a baseline understanding of this disorder based on current curriculum is reviewed, with the objective of improving future physicians’ awareness of obstetric fistula. Despite a low survey response rate, there was a significant association between greater knowledge about causes, treatment, and complications of obstetric fistula and advanced years in medical school. However, the fourth year medical students averaged only a 70.5 percent of correct responses on the survey, indicating room for improvement in addressing this topic during medical school. ^

Comparison of machine learning approaches and statistical methods for estimation of airborne chemical exposures

Accurate quantitative estimation of exposure using retrospective data has been one of the most challenging tasks in the exposure assessment field. To improve these estimates, some models have been developed using published exposure databases with their corresponding exposure determinants. These models are designed to be applied to reported exposure determinants obtained from study subjects or exposure levels assigned by an industrial hygienist, so quantitative exposure estimates can be obtained. ^ In an effort to improve the prediction accuracy and generalizability of these models, and taking into account that the limitations encountered in previous studies might be due to limitations in the applicability of traditional statistical methods and concepts, the use of computer science- derived data analysis methods, predominantly machine learning approaches, were proposed and explored in this study. ^ The goal of this study was to develop a set of models using decision trees/ensemble and neural networks methods to predict occupational outcomes based on literature-derived databases, and compare, using cross-validation and data splitting techniques, the resulting prediction capacity to that of traditional regression models. Two cases were addressed: the categorical case, where the exposure level was measured as an exposure rating following the American Industrial Hygiene Association guidelines and the continuous case, where the result of the exposure is expressed as a concentration value. Previously developed literature-based exposure databases for 1,1,1 trichloroethane, methylene dichloride and, trichloroethylene were used. ^ When compared to regression estimations, results showed better accuracy of decision trees/ensemble techniques for the categorical case while neural networks were better for estimation of continuous exposure values. Overrepresentation of classes and overfitting were the main causes for poor neural network performance and accuracy. Estimations based on literature-based databases using machine learning techniques might provide an advantage when they are applied to other methodologies that combine `expert inputs' with current exposure measurements, like the Bayesian Decision Analysis tool. The use of machine learning techniques to more accurately estimate exposures from literature-based exposure databases might represent the starting point for the independence from the expert judgment.^