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Linear Changes (linear + change)
Selected AbstractsDrug effect on EEG connectivity assessed by linear and nonlinear couplingsHUMAN BRAIN MAPPING, Issue 3 2010Joan F. Alonso Abstract Quantitative analysis of human electroencephalogram (EEG) is a valuable method for evaluating psychopharmacological agents. Although the effects of different drug classes on EEG spectra are already known, interactions between brain locations remain unclear. In this work, cross mutual information function and appropriate surrogate data were applied to assess linear and nonlinear couplings between EEG signals. The main goal was to evaluate the pharmacological effects of alprazolam on brain connectivity during wakefulness in healthy volunteers using a cross-over, placebo-controlled design. Eighty-five pairs of EEG leads were selected for the analysis, and connectivity was evaluated inside anterior, central, and posterior zones of the scalp. Connectivity between these zones and interhemispheric connectivity were also measured. Results showed that alprazolam induced significant changes in EEG connectivity in terms of information transfer in comparison with placebo. Trends were opposite depending on the statistical characteristics: decreases in linear connectivity and increases in nonlinear couplings. These effects were generally spread over the entire scalp. Linear changes were negatively correlated, and nonlinear changes were positively correlated with drug plasma concentrations; the latter showed higher correlation coefficients. The use of both linear and nonlinear approaches revealed the importance of assessing changes in EEG connectivity as this can provide interesting information about psychopharmacological effects. Hum Brain Mapp, 2010. © 2009 Wiley-Liss, Inc. [source] Early detection of relapse in panic disorderACTA PSYCHIATRICA SCANDINAVICA, Issue 5 2004M. R. Mavissakalian Objective:, To explore predictive models of relapsing based on change in symptoms at a time when panic disorder patients are still in remission following discontinuation of antidepressants. Method:, Forty-seven subjects, who were randomized to double-blind placebo and who had valid data at four time points: pretreatment, randomization to placebo substitution, an assessment on placebo prior to the last assessment or relapse and their last assessment (relapsers n = 15, non-relapsers n = 32) were studied using descriptive, growth curve analysis and logistic regression methodologies. Results:, Measures of generalized anxiety, fearfulness and disability at work and at home were better predictors of relapse than measures of panic and anxiety sensitivity. Logistic regression models using any one of these four general variables and its linear change correctly predicted relapse for 78.7,84.4% of the study subjects. Conclusion:, It is possible to gauge, with a fair degree of accuracy, the probability of relapsing in panic disorder patients who have discontinued serotonergic antidepressants 2 months prior to the return of panic. [source] Asymptotic upper bounds for the errors of Richardson extrapolation with practical application in approximate computationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2009Aram Soroushian Abstract The results produced by Richardson extrapolation, though, in general, very accurate, are inexact. Numerical evaluation of this inexactness and implementation of the evaluation in practice are the objectives of this paper. First, considering linear changes of errors in the convergence plots, asymptotic upper bounds are proposed for the errors. Then, the achievement is extended to the results produced by Richardson extrapolation, and finally, an error-controlling procedure is proposed and successfully implemented in approximate computations originated in science and engineering. Copyright © 2009 John Wiley & Sons, Ltd. [source] Morphological variation and floral abnormalities in a trigger plant across a narrow altitudinal gradientAUSTRAL ECOLOGY, Issue 7 2009ARY A. HOFFMANN Abstract Local adaptation in alpine plants has been demonstrated across wide altitudinal gradients, but has rarely been examined across the alpine-to-montane transition that often encompasses only a few hundred metres. Here we characterize morphological variation in leaf and floral characteristics of the trigger plant Stylidium armeria along a narrow altitudinal gradient in the Bogong High Plains in Victoria. Across this gradient, which encompasses the high-elevation limit of this species, linear changes were found for floral scape height, leaf length and flower number. All these traits decreased with increasing altitude, whereas the frequency of abnormal flowers increased. When plants were grown in a common garden environment, an altitudinal pattern for flower abnormalities was no longer detected. However, altitudinal patterns for leaf length and scape height were maintained, albeit weaker than in the field. This indicates heritable variation for these morphological traits; the altitudinal patterns are likely to reflect the effects of selection by environmental factors that vary with altitude. Selection pressures remain to be identified but have generated both cogradient and countergradient patterns of variation. [source] | ||||||||||