Probing the time course of nonlinear discriminations during human electrodermal conditioning

Animal-based theories of Pavlovian conditioning propose that patterning discriminations are solved using unique cues or immediate configuring. Recent studies with humans, however, provided evidence that in positive and negative patterning two different rules are utilized. The present experiment was designed to provide further support for this proposal by tracking the time course of the allocation of cognitive resources. One group was trained in a positive patterning; schedule (A-, B-, AB+) and a second in a negative patterning schedule (A+, B+, AB-). Electrodermal responses and secondary task probe reaction time were measured. In negative patterning, reaction times were slower during reinforced stimuli than during non-reinforced stimuli at both probe positions while there were no differences in positive patterning. These results support the assumption that negative patterning is solved using a rule that is more complex and requires more resources than does the rule employed to solve positive patterning. (C) 2001 Elsevier Science (USA).

Latent inhibition and schizophrenia: Pavlovian conditioning of autonomic responses

Latent inhibition (LI) is an important model for understanding cognitive deficits in schizophrenia, Disruption of LI is thought to result from an inability to ignore irrelevant stimuli. The study investigated LI in schizophrenic patients by using Pavlovian conditioning of electrodermal responses in a complete within-subject design. Thirty-two schizophrenic patients, ( 16 acute. unmedicated and 16 medicated patients) and 16 healthy control subjects (matched with respect to age and gender) participated in the study. The experiment consisted of two stages: preexposure and conditioning. During preexposure two visual stimuli were presented, one of which served as the to-be-conditioned stimulus (CSp +) and the other one was the not-to-be-conditioned stimulus (CSp -) during the following conditioning ( = acquisition). During acquisition. two novel visual stimuli (CSn + and CSn -) were introduced. A reaction time task was used as the unconditioned stimulus (US). LI was defined as the difference in response differentiation observed between proexposed and non-preexposed sets of CS + and CS -. During preexposure. the schizophrenic patients did not differ in electrodermal responding from the control subjects, neither concerning the extent of orienting nor the course of habituation. The exposure to novel stimuli at the beginning of the acquisition elicited reduced orienting responses in unmedicated patients compared to medicated patients and control subjects, LI was observed in medicated schizophrenic patients and healthy controls. but not in acute unmedicated patients. Furthermore LI was found to be correlated with the duration of illness: it was attenuated in patients who had suffered their first psychotic episode. (C) 2002 Elsevier Science B.V. All rights reserved.

ROM-based computation: Quantum versus classical

We introduce a model of computation based on read only memory (ROM), which allows us to compare the space-efficiency of reversible, error-free classical computation with reversible, error-free quantum computation. We show that a ROM-based quantum computer with one writable qubit is universal, whilst two writable bits are required for a universal classical ROM-based computer. We also comment on the time-efficiency advantages of quantum computation within this model.

The modeling of turbulent reactive flows based on multiple mapping conditioning

A new modeling approach-multiple mapping conditioning (MMC)-is introduced to treat mixing and reaction in turbulent flows. The model combines the advantages of the probability density function and the conditional moment closure methods and is based on a certain generalization of the mapping closure concept. An equivalent stochastic formulation of the MMC model is given. The validity of the closuring hypothesis of the model is demonstrated by a comparison with direct numerical simulation results for the three-stream mixing problem. (C) 2003 American Institute of Physics.

Classical approach to interpretation of the charge-dependence of peptide mobilities obtained by capillary zone electrophoresis

Published mobility measurements obtained by capillary zone electrophoresis of human growth hormone peptides are described reasonably well by the classical theoretical relationships for electrophoretic migration. This conformity between theory and experiment has rendered possible a more critical assessment of a commonly employed empirical relationship between mobility (u), net charge (z) and molecular mass (M) of peptides in capillary electrophoresis. The assumed linear dependence between u and z/M-2/3 is shown to be an approximate description of a shallow curvilinear dependence convex to the abscissa. An improved procedure for the calculation of peptide charge (valence) is also described. (C) 2003 Elsevier B.V. All rights reserved.

Microcanonical temperature for a classical field: Application to Bose-Einstein condensation

We show that the projected Gross-Pitaevskii equation (PGPE) can be mapped exactly onto Hamilton's equations of motion for classical position and momentum variables. Making use of this mapping, we adapt techniques developed in statistical mechanics to calculate the temperature and chemical potential of a classical Bose field in the microcanonical ensemble. We apply the method to simulations of the PGPE, which can be used to represent the highly occupied modes of Bose condensed gases at finite temperature. The method is rigorous, valid beyond the realms of perturbation theory, and agrees with an earlier method of temperature measurement for the same system. Using this method we show that the critical temperature for condensation in a homogeneous Bose gas on a lattice with a uv cutoff increases with the interaction strength. We discuss how to determine the temperature shift for the Bose gas in the continuum limit using this type of calculation, and obtain a result in agreement with more sophisticated Monte Carlo simulations. We also consider the behavior of the specific heat.

Traffic control: p120-catenin acts as a gatekeeper to control the fate of classical cadherins in mammalian cells

Proteins of the p120 family have been implicated in the regulation of cadherin-based cell adhesion, but their relative importance in this process and their mechanism of action have remained less clear. Three papers in this issue suggest that p120 plays a key role in maintaining normal levels of cadherin in mammalian cells, and that it may do so by regulating cadherin trafficking.

Evaluative learning in human Pavlovian conditioning: Extinct, but still there?

Previous studies of human affective learning, the acquisition of likes and dislikes, provided evidence that extinction training does not affect changes in conditional stimulus (CS) valence as indexed by paper/pencil ratings. Experiment 1 (N = 32) investigated whether this is an artifact of the CS valence assessment, which is taken in test sessions before and after training. Pleasantness ratings were collected in pre/post training tests and, for half of the participants, on-line during training. Rated unpleasantness of the CS that preceded the aversive US (CS+) increased during acquisition and decreased during extinction back to neutral. However, as in previous studies, post extinction paper/pencil ratings revealed the maintenance of rated CS+ unpleasantness. Experiment 2 (N = 34) replicated this finding for two measures of CS valence, paper/pencil and the continuous measure used during training. The present results indicate that previous reports of failures to find extinction of affective learning may reflect renewal rather than maintenance of acquired CS valence across extinction training. (C) 2003 Elsevier Science (USA). All rights reserved.

The effects of unconditional stimulus valence and conditioning paradigm on verbal, skeleto-motor, and autonomic indices of human Pavlovian conditioning

The effects of unconditional stimulus (US) valence (aversive electro-tactile stimulus vs. nonaversive imperative stimulus of a RT task) and conditioning paradigm (delay vs. trace) on affective learning as indexed by verbal ratings of conditional stimulus (CS) pleasantness and blink startle modulation and on relational learning as indexed by electrodermal responses were investigated. Affective learning was not affected by the conditioning paradigm; however, electrodermal responses and blink latency shortening indicated delayed learning in the trace procedure. Changes in rated CS pleasantness were found with the aversive US, but not with the non-aversive US. Differential conditioning as indexed by electrodermal responses and startle modulation was found regardless of US valence. The finding of significant differential blink modulation and electrodermal responding in the absence of a change in rated CS pleasantness as a result of conditioning with a non-aversive US was replicated in a second experiment. These results seem to indicate that startle modulation during conditioning is mediated by the arousal level of the anticipated US, rather than by the valence of the CS. (C) 2002 Elsevier Science (USA). All rights reserved.

Single-subject research designs and data analyses for assessing elite athletes' conditioning

Research in conditioning (all the processes of preparation for competition) has used group research designs, where multiple athletes are observed at one or more points in time. However, empirical reports of large inter-individual differences in response to conditioning regimens suggest that applied conditioning research would greatly benefit from single-subject research designs. Single-subject research designs allow us to find out the extent to which a specific conditioning regimen works for a specific athlete, as opposed to the average athlete, who is the focal point of group research designs. The aim of the following review is to outline the strategies and procedures of single-subject research as they pertain to.. the assessment of conditioning for individual athletes. The four main experimental designs in single-subject research are: the AB design, reversal (withdrawal) designs and their extensions, multiple baseline designs and alternating treatment designs. Visual and statistical analyses commonly used to analyse single-subject data, and advantages and limitations are discussed. Modelling of multivariate single-subject data using techniques such as dynamic factor analysis and structural equation modelling may identify individualised models of conditioning leading to better prediction of performance. Despite problems associated with data analyses in single-subject research (e.g. serial dependency), sports scientists should use single-subject research designs in applied conditioning research to understand how well an intervention (e.g. a training method) works and to predict performance for a particular athlete.

IR as Practical Philosophy: Defining a 'Classical Approach'

This article addresses the centrality of normativity to IR (International Relations) by engaging in an investigation of the meaning of a 'classical' approach (Bull 1969). It demonstrates how a classical approach, properly understood, might provide common ground for IR theorists. The substantive argument is that IR can benefit from reflection on the classical understanding of the relationship between theory and practice, and in particular on the understanding of this relationship provided by philosophical hermeneutics. Philosophical hermeneutics is an approach to the human sciences informed by Aristotle's conception of a practical philosophy. A practical philosophy in the classical sense sees theory as a moral and political inquiry involving a body of knowledge and a philosophy of practice engaging in reflection upon the nature of the good life and the means to achieve it.

Classical cadherin adhesion molecules: coordinating cell adhesion, signaling and the cytoskeleton

Classical cadherin adhesion molecules are fundamental determinants of tissue organization in both health and disease. Recent advances in understanding the molecular and cellular basis of cadherin function have revealed that these adhesion molecules serve as molecular couplers, linking cell surface adhesion and recognition to both the actin cytoskeleton and cell signalling pathways. We will review some of these developments. to provide an overview of progress in this rapidly-developing area of cell and developmental biology.