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At least 1,783 records · Page 99Linked to original sources
PubMed2002

Mental models and counterfactual thoughts about what might have been.

Counterfactual thoughts about what might have been ('if only em leader ') are pervasive in everyday life. They are related to causal thoughts, they help people learn from experience and they influence diverse cognitive activities, from creativity to probability judgements. They give rise to emotions and social ascriptions such as guilt, regret and blame. People show remarkable regularities in the aspects of the past they mentally 'undo' in their counterfactual thoughts. These regularities provide clues about their mental representations and cognitive processes, such as keeping in mind true possibilities, and situations that are false but temporarily supposed to be true.

Journal Article↗
PubMed2004

Outlasting excitability shifts induced by direct current stimulation of the human brain.

tDCS appears to be a promising tool in neuroplasticity research with some perspectives in clinical neurophysiology. It is closely related to modulation of cortical excitability and activity which are key mechanisms for modulating neuroplasticity. Long-term potentiation and long-term depression-like effects have been shown to be involved in learning processes in animal studies so far. Stimulation with weak direct currents is capable of inducing stimulation-polarity-dependent, prolonged, diminutions or elevations of cortical activity and excitability, most probably elicited by a hyper- or depolarisation of resting membrane potentials. Moreover, these modulations are functionally important, since they affect learning processes and epileptic activity. Here excitability changes have been accomplished in the human by non-invasive transcranial direct current stimulation (tDCS). They share some important features with these well-known neuroplastic changes: The duration of the effects depends on stimulation duration and intensity, they are of intracortical origin, and the prolonged effects depend on NMDA-receptor activity. Thus, this technique is a promising method in the field of neuroplastic research in animals and humans and could evolve as a therapeutic tool in some neuro-psychiatric disorders which benefit from modulation of cortical excitability.

Brain↗
PubMedDate not supplied

Immunohistochemical analysis and prognostic value of cathepsin D determination in laryngeal squamous cell carcinoma.

Cathepsin D, a protease with the capability of degrading matrix proteins, is implicated in the process of breast and colorectal cancer invasion and metastasis. Biochemical studies in laryngeal cancer have shown a potential prognostic significance of cathepsin D content determination. We studied immunohistochemical positivity of cathepsin D in tumor epithelium and stroma of 61 surgical specimens of squamous cell laryngeal cancer. Immunohistochemical reaction was quantitatively assessed using a PC-based image analysis system SFORM-VAMS. The results were correlated to clinical and morphological parameters and survival. Immunohistochemical positivity was noted in neoplastic cells and tumor stroma. Significant prognostic value for cathepsin D was established separately for epithelial tumor component and tumor stroma using log-rank test, the Cox proportional hazards regression model, and C4.5 machine learning system. In all groups, patients above the median cathepsin D staining showed significantly shorter survival time. C4.5 machine learning system extracted cutoff values for the decision tree that defines the probabilities of patients survival and death with high sensitivity (92.8% alive, 73.6% dead), 100% specificity, and 86.9% accuracy. This makes immunohistochemical cathepsin D estimation an independent prognostic parameter in laryngeal carcinomas within a 5-year period from the time of tumor surgery.

Carcinoma, Squamous Cell↗
PubMed2003

Item recognition memory and the receiver operating characteristic.

Four experiments were conducted to investigate the effects of study time, study repetition, semantic and orthographic similarity, and category length on item recognition memory receiver operating characteristics (ROCs). Analyses of ROC shape rejected A. P. Yonelinas's (1994) dual-process model. The normal unequal variance signal-detection model provided a better account of the data, except for a small but consistent excess of high-confidence errors. It was found that z-transformed ROC slope was increased by similarity, category length, and study item repetition, rejecting R. Ratcliff, G. McKoon, and M. Tindall's (1994) "constancy-of-slopes" generalization for these variables, but slope was relatively unaffected by massed study time.

Humans↗
PubMed2002

The evolution of inaccurate mimics.

Instances of strikingly accurate Batesian mimicry (in which a palatable prey organism closely resembles an aversive model) are often cited to illustrate the power of natural selection. Less attention has been paid to those mimics, such as many hoverfly (Syrphidae) mimics of wasps or bees, that resemble their models only poorly. Attempts to provide an adaptive explanation for imperfect mimicry have suggested that what seems a crude resemblance to human observers may appear a close match to predators, or that inaccurate mimics may bear a general resemblance to several different model species. I show here, however, that truly inaccurate mimicry of a single model organism may be favoured over perfect resemblance, by kin selection. Signal detection theory predicts that predators will modify their level of discrimination adaptively in response to the relative frequencies and similarity of models and mimics. If models are rare and/or weakly aversive, greater local similarity of mimics can thus lead to greater attack rates. Where individual mimics are related to others in their vicinity, kin selection will then oppose the evolution of accurate mimicry.

Adaptation, Physiological↗
PubMedDate not supplied

Problems of aging: urinary incontinence prevention.

This exploratory study focused on identification of risk factors, the criteria establishing risk, and associated preventive strategies for diagnosis and treatment of urinary incontinence. Sixty-eight women were assessed for actual and potential urinary incontinence. Data collected each month included demographics, medical diagnoses, medications, environmental features, mobility, mental status, and presence or absence of eleven probable risk factors drawn from an extensive review of the literature. Women learned one or more noninvasive treatment strategies linked to their risks. Pretreatment analysis identified 55 women at risk and 13 as incontinent. Posttreatment, 9 were incontinent (1 at-risk woman became incontinent). Greater numbers of risk factors were experienced by the incontinent women. Posttreatment, 7 of the incontinent women eliminated from 1 to 5 risk factors. Risk-factor identification and correction are essential for concerted prevention efforts. The results are clinically important.

Aged↗
PubMed2005

Can video games be used to predict or improve laparoscopic skills?

BACKGROUND AND PURPOSE: Performance of laparoscopic surgery requires adequate hand-eye coordination. Video games are an effective way to judge one's hand-eye coordination, and practicing these games may improve one's skills. Our goal was to see if there is a correlation between skill in video games and skill in laparoscopy. Also, we hoped to demonstrate that practicing video games can improve one's laparoscopic skills. SUBJECTS AND METHODS: Eleven medical students (nine male, two female) volunteered to participate. On day 1, each student played three commercially available video games (Top Spin, XSN Sports; Project Gotham Racing 2, Bizarre Creations; and Amped 2, XSN Sports) for 30 minutes on an X-box (Microsoft, Seattle, WA) and was judged both objectively and subjectively. Next, the students performed four laparoscopic tasks (object transfer, tracing a figure-of-eight, suture placement, and knot-tying) in a swine model and were assessed for time to complete the task, number of errors committed, and hand-eye coordination. The students were then randomized to control (group A) or "training" (i.e., video game practicing; group B) arms. Two weeks later, all students repeated the laparoscopic skills laboratory and were reassessed. RESULTS: Spearman correlation coefficients demonstrated a significant relation between many of the parameters, particularly time to complete each task and hand-eye coordination at the different games. There was a weaker association between video game performance and both laparoscopic errors committed and hand-eye coordination. Group B subjects did not improve significantly over those in group A in any measure (P >0.05 for all). CONCLUSION: Video game aptitude appears to predict the level of laparoscopic skill in the novice surgeon. In this study, practicing video games did not improve one's laparoscopic skill significantly, but a larger study with more practice time could prove games to be helpful.

Adult↗
PubMed1992

Breast reconstruction with tissue expanders: obtaining an optimal result.

A large personal experience with breast reconstruction using tissue expanders (149 patients with Radovans, and more than 150 patients with Beckers), with many suboptimal results especially in the early learning stages, has brought about changes in approach offering a much higher probability of acceptable breasts. This report attempts to combine multiple factors useful in yielding such results. Areas addressed include immediate versus delayed reconstruction, selection of candidates, selection of expander type, appropriate placement of expander at a site minimizing the requirement for pocket modification, choosing the optimal size expander, importance of maximal overexpansion to yield a good submammary fold, and means of determining adequate overexpansion to match an unmodified contralateral breast and the risks inherent in overexpansion. Timing, interval, and length of maintenance of hyperexpansion are described along with deflation and timing of port removal. Both the skate and star techniques of nipple and areolar reconstruction in the hyperexpanded patient yield very acceptable results despite thinned skin and minimal subcutaneous tissue. Good, satisfactory, and suboptimal clinical results will be presented. In our experience, tissue expansion reconstruction offers distinct advantages in a large majority of patients with the proviso that patients are willing to accept the time required for hyperexpansion and the waiting period for deflation.

Female↗
PubMed2000

Influence of fatigue on EMG/force ratio and cocontraction in cycling.

PURPOSE: The purpose of the present study was to observe force and power losses and electromyographic manifestations of fatigue during repeated sprints performed on a friction-loaded cycle ergometer. METHODS: Ten subjects performed 15 maximal 5-s sprints with 25-s rests between them. Power, velocity, and torque were measured during sprints 1 and 13 and during two submaximal constant-velocity (50 rpm) periods of cycling performed before and after the sprints. The EMG signals of five leg muscles were stored to determine the EMG/force ratio of power producer muscles and the coactivation of antagonist muscles. The power producer muscles were activated to the same level during sprints 1 and 13, despite a loss of force, whereas the vastus lateralis muscle was recruited more during the submaximal cycling period under fatigue conditions. RESULTS: This led to an increased EMG/force ratio for the power producer muscles, indicating the peripheral fatigue status of these muscles. Antagonist muscles were less activated during the sprints after fatigue; whereas they stayed unchanged during the last submaximal cycling period. CONCLUSIONS: This suggests that there is a decrease in coactivation as agonist force is lost. This decrease in coactivation under fatigue conditions has not been previously reported and is probably due to the training status of the subjects. Subjects may have learned to better use their antagonist muscles to efficiently transfer force and power to the rotating pedal. This coordination can be adapted to cope with fatigue of the power producer muscles.

Adult↗
PubMed1999

Higher-order probabilistic perceptrons as Bayesian inference engines.

An explicit structural connection is established between the Bayes optimal classifier operating on K binary input variables and a corresponding two-layer perceptron having normalized output activities and couplings from input to output units of all orders up to K. With suitable modification of connection weights and biases, such a higher-order probabilistic perceptron should in principle be able to learn the statistics of the classification problem and match the a posteriori probabilities given by Bayes optimal inference. Specific training algorithms are developed that allow this goal to be approximated in a controlled variational sense. An application to the task of discriminating between stable and unstable nuclides in nuclear physics yields network models with predictive performance comparable to the best that has been achieved with conventional multilayer perceptrons containing only pairwise connections.

Journal Article↗
PubMed2005

A model selection algorithm for a posteriori probability estimation with neural networks.

This paper proposes a novel algorithm to jointly determine the structure and the parameters of a posteriori probability model based on neural networks (NNs). It makes use of well-known ideas of pruning, splitting, and merging neural components and takes advantage of the probabilistic interpretation of these components. The algorithm, so called a posteriori probability model selection (PPMS), is applied to an NN architecture called the generalized softmax perceptron (GSP) whose outputs can be understood as probabilities although results shown can be extended to more general network architectures. Learning rules are derived from the application of the expectation-maximization algorithm to the GSP-PPMS structure. Simulation results show the advantages of the proposed algorithm with respect to other schemes.

Algorithms↗
PubMed1985

Suicide and suicide attempts in the European Economic Community: an analysis of trends, with special emphasis upon trends among the young.

An attempt is made to explain the increase in adolescent suicidal behavior reported for most countries in the European Economic Community over the last two decades, within the framework of a social learning theory. A typology of suicidal acts based on an outcome-expectancy model is proposed that would make intelligible the observed positive correlation between the incidence of lethal and nonlethal suicidal acts, the latter having grown to epidemic proportions among the young. This epidemic can be attributed to the interplay of three groups of factors, namely, the socialization of a specific problem-solving behavior repertoire, socioeconomic conditions, and attitudes toward suicide. The implications for suicide prevention are briefly discussed.

Adolescent↗