bluuebunny/crossref_metadata_2025 huggingface dataset:
BIOLOGY ANDPOLITICS: Linking Nature and Nurture
Authors: Masters R.D.
Published: July 2002

▪ Abstract  Although millions of Americans take psychoactive medicines (e.g. Prozac and Ritalin), few social scientists believe biological theories and findings should be integrated with research on human behavior. Four topics illustrate current studies linking politics and the life sciences: (a) Developments in genetics and medicine indicate that governmental policies have greatly underrated the dangers posed by radiation and the social transformations that will result from DNA sequencing. (b) Research on brain structures and neurochemistry shows how toxic chemicals undermine normal emotions and behavior. Heavy metal burdens are higher in violent criminals, and exposure to these toxins is significantly correlated with rates of violence (controlling for socioeconomic, ethnic, and demographic factors). (c) An untested chemical used to treat water supplied to 140 million Americans significantly increases both odds of dangerous lead uptake and behavioral dysfunctions in children and adults. (d) The complexity of gene-environment interactions challenges accepted theories of gender, sociopolitical inequalities, ethnocentrism, and history. Such research in biopolitics can illuminate policy controversies in education, substance abuse, and crime.
CREATIVE HYPOTHESIS GENERATING IN PSYCHOLOGY: Some Useful Heuristics
Authors: McGuire William J.
Published: July 2002

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▪ Abstract  To correct a common imbalance in methodology courses, focusing almost entirely on hypothesis-testing issues to the neglect of hypothesis-generating issues which are at least as important, 49 creative heuristics are described, divided into 5 categories and 14 subcategories. Each of these heuristics has often been used to generate hypotheses in psychological research, and each is teachable to students. The 49 heuristics range from common sense perceptiveness of the oddity of natural occurrences to use of sophisticated quantitative data analyses in ways that provoke new insights.
Theories of Associative Learning in Animals
Authors: Pearce John M. , Bouton Mark E.
Published: July 2002

▪ Abstract  Theories of associative learning are concerned with the factors that govern association formation when two stimuli are presented together. In this article we review the relative merits of the currently influential theories of associative learning. Some theories focus on the role of attention in association formation, but differ in the rules they propose for determining whether or not attention is paid to a stimulus. Other theories focus on the nature of the association that is formed, but differ as to whether this association is regarded as elemental, configural, or hierarchical. Recent developments involve modifications to existing theories in order to account for associative learning between two stimuli, A and B, when A is accompanied, not by B, but by a stimulus that has been paired with B. The implications of the theories for understanding how humans derive causal judgments and solve categorization problems is considered.
Effects of Psychological and Social Factors on Organic Disease: A Critical Assessment of Research on Coronary Heart Disease
Authors: Krantz David S. , McCeney Melissa K.
Published: July 2002

▪ Abstract  An extensive research literature in the behavioral sciences and medicine suggests that psychological and social factors may play a direct role in organic coronary artery disease (CAD) pathology. However, many in the medical and scientific community regard this evidence with skepticism. This chapter critically examines research on the impact of psychological and psychosocial factors on the development and outcome of coronary heart disease, with particular emphasis on studies employing verifiable outcomes of CAD morbidity or mortality. Five key variables identified as possible psychosocial risk factors for CAD are addressed: acute and chronic stress, hostility, depression, social support, and socioeconomic status. Evidence regarding the efficacy of psychosocial interventions is also presented. It is suggested that, taken as a whole, evidence for a psychological and social impact on CAD morbidity and mortality is convincing. However, continued progress in this area requires multidisciplinary research integrating expertise in cardiology and the behavioral sciences, and more effective efforts to communicate research findings to a biomedical audience.
THE HUMAN HEALTH EFFECTS OF DDT (DICHLORODIPHENYLTRICHLOROETHANE) AND PCBS (POLYCHLORINATED BIPHENYLS) AND AN OVERVIEW OF ORGANOCHLORINES IN PUBLIC HEALTH
Authors: Longnecker Matthew P. , Rogan Walter J. , Lucier George
Published: July 2002

▪ Abstract  Organochlorines are a diverse group of persistent synthetic compounds, some of which are detectable in nearly everyone. Many organochlorines are endocrine disruptors or carcinogens in experimental assays. p,p′-DDE (dichlorodiphenyl- dichloroethene) and PCBs (polychlorinated biphenyls) comprise the bulk of orga- nochlorine residues in human tissues. We reviewed relevant human data cited in the 1991–1995 Medline database and elsewhere. High-level exposure to selected organochlorines appears to cause abnormalities of liver function, skin (chloracne), and the nervous system. Of more general interest, however, is evidence suggesting insidious effects of background exposure. Of particular concern is the finding of neonatal hypotonia or hyporeflexia in relation to PCB exposure. The epidemiologic data reviewed, considered in isolation, provide no convincing evidence that organochlorines cause a large excess number of cancers. A recent risk assessment that considered animal data, however, gives a cancer risk estimate for background exposure to dioxin and dioxin-like compounds (e.g. some PCBs) with an upper bound in the range of 10−4 per year.
MUSINGS ON SIXTY YEARS IN PUBLIC HEALTH
Authors: Breslow Lester
Published: July 2002

▪ Abstract  These reflections on six decades in public health work come from both personal experiences and observations in the field. Attention is given to changes in health problems during the period and how public health workers have responded to them. The commentary also touches on how one proceeds in public health, includes suggestions for effectiveness, notes some difficulties encountered, and briefly describes health progress. The evolution of public health to encompass a much broader scope of activity than in the 1930s and how that has come about is emphasized.
Cultural and Social-Structural Explanations of Cross-National Psychological Differences
Authors: Schooler Carmi
Published: July 2002

This chapter examines cross-national differences in individual values, attitudes, and behaviors. The central question raised is how social-structural and cultural factors account for the differences found. After discussing a series of theoretical issues raised by this question, the chapter reviews the findings of four quantitative sociological research programs on modern cross-national differences. The program on individual modernity led by Alex Inkeles established that social-structural conditions associated with industrialization are linked to an increase in individuals' being open to new experience, rejecting traditional authority, and taking a rational, ambitious, orderly approach to both work and human problems. The cross-national research on the Kohn-Schooler hypothesis that self-directed work increases intellectual functioning and self-directed orientations confirmed the generality of that hypothesis and established that the social status and social class differences in these psychological characteristics found within different countries are largely the result of social-structurally determined differences in the opportunity for occupational self-direction. Eric Wright's cross-national research program on class structure and class consciousness provides evidence that in a range of countries social classes directly affect political attitudes, while acting as tangible barriers to mobility and personal relationships. The research deriving from John Meyer's theories on institutionalization highlights the importance of institutions and socially constructed views of reality for the development and maintenance of cross-national differences and similarities in cultural values and their behavioral embodiment. All four of the programs provide evidence of the continuing importance of historically determined cultural differences. All are also congruent with the hypothesis that speed of change generally decreases as we go from psychological to social-structural to cultural levels of phenomena—a possibility whose confirmation would provide a valuable tool for understanding how culture and social structure affect cross-national differences in values and behavior.
Wealth Inequality in the United States
Authors: Keister Lisa A. , Moller Stephanie
Published: July 2002

Wealth ownership in the United States has long been concentrated in the hands of a small minority of the population, yet researchers have paid relatively little attention to the causes and consequences of this inequality. In this essay, we review the literature that does exist on wealth accumulation and distribution. We begin with an examination of the reasons that wealth inequality has received little empirical attention. We then discuss methods of creating empirical estimates of wealth accumulation and distribution, and we present some estimates of recent trends in wealth inequality. We explore a diverse collection of research that explains these trends, covering treatments of aggregate influences and individual and household factors. We conclude the chapter with a review of research on intergenerational processes and wealth mobility.
Functional Significance of Prorenin Internalization in the Rat Heart
Authors: Peters Jörg , Farrenkopf Raphaela , Clausmeyer Susanne , Zimmer Jutta , Kantachuvesiri Surasak , Sharp Matthew G.F. , Mullins John J.
Published: July 2002

Intracardiac renin is considered to be involved in the pathogenesis of cardiac hypertrophy, fibrosis, and myocardial infarction. Cardiac renin is predominantly derived from the circulation, because preprorenin is not expressed locally and uptake of renin has been demonstrated. One mechanism of internalization recently described involves the mannose-6-phosphate receptor and requires glycosylation of renin. Based on previous observations, we considered the existence of another pathway of uptake, not requiring glycosylation and predominantly involving prorenin. This hypothesis and its functional consequences were investigated in vitro and in vivo. We demonstrate that isolated adult cardiomyocytes internalize unglycosylated prorenin, which is followed by the generation of angiotensins. We further show that transgenic rats, expressing the
ren-2
d
renin gene in an inducible manner, exhibit markedly enhanced levels of unglycosylated renin within intracellular compartments in the heart as a consequence of the induction of hepatic transgene expression and the rise of circulating unglycosylated prorenin levels. Because in this model severe cardiac damage occurs as a consequence of the rise of circulating prorenin levels, internalization of prorenin into cardiac cells is likely to play a key role in this process.
Hemicraniectomy and Moderate Hypothermia in Patients With Severe Ischemic Stroke
Authors: Georgiadis D. , Schwarz S. , Aschoff A. , Schwab S.
Published: July 2002

Background and Purpose

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We compared the clinical course of 36 consecutive patients with severe acute ischemic stroke (more than two thirds of the middle cerebral artery territory) treated with hemicraniectomy (CE; n=17) or moderate hypothermia (MH; n=19) in terms of intracranial pressure control, mortality, and specific treatment parameters.

Methods

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Over a period of 18 months, patients with severe ischemic stroke were treated with CE when the nondominant hemisphere was affected and with MH when the dominant hemisphere was affected. MH (33°C) was induced with either cold blankets and fans (n=11) or endovascular cooling (n=8). Intracranial pressure was monitored invasively in all cases.

Results

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Age, sex, cranial CT findings, level of consciousness, and time to treatment were similar between the 2 groups; significant differences were noted in National Institute of Health Stroke Scale (NIHSS) score (20 [range, 18 to 22] and 17 [range, 16 to 18] for MH and CE, respectively) but were not present when NIHSS score was corrected for aphasia (17 [range, 15 to 19] and 17 [range, 16 to 18] for MH and CE, respectively). Mortality was 12% for CE and 47% for MH; 1 patient treated with MH died as a result of treatment complications (sepsis) and 3 of intracranial pressure crises that occurred during rewarming. Duration of mechanical ventilation and of neurological intensive care unit stay did not significantly differ, but duration of catecholamine application and maximal catecholamine dosage were significantly higher in the MH group.

Conclusions

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In patients with severe ischemic stroke, CE results in lower mortality and lower complication rates compared with MH. Both treatment modalities, however, are associated with intensive medical treatment and a prolonged stay in the neurological intensive care unit.
What Single Voice? European Institutions and EU–U.S. Trade Negotiations
Authors: Meunier Sophie
Published: July 2002

The member states of the European Union (EU) have transferred their sovereignty over trade policymaking to the supranational level. When entering into trade negotiations with third countries, they must first reach a common bargaining position among themselves and later defend that position with a “single voice” at the international table. How do the institutional rules, through which the fifteen different voices are aggregated into a single one, affect international outcomes? Differentiating between a “conservative” and a “reformist” negotiating context, I argue that voting rules and negotiating competence in the EU determine both the probability that the negotiating parties conclude an international agreement and the substantive outcome of the negotiations. The recent EU–U.S. trade negotiations on agriculture, public procurement, and open skies are all evidence that, for a given distribution of preferences, internal EU institutional mechanisms affect the outcomes of international trade agreements.
Liberal Social Reconstruction and the Resolution of Civil Wars in Central America
Authors: Peceny Mark , Stanley William
Published: July 2002

The international community, in its efforts to overcome the security dilemmas that inhibit conflict resolution, need not always offer forceful security guarantees to combatants in civil wars. We argue that noncoercive, liberal international intervention can end civil wars. As suggested by a constructivist perspective and the insights of the democratic peace, the promotion of liberal democracy can successfully resolve civil wars by transforming the identities and institutions of the combatants. We develop this argument by examining the resolution of civil wars in Central America during the 1990s. Of the Central American cases, Nicaragua, the country subject to the strongest security guarantees, has been the least stable of the three. El Salvador and Guatemala, in contrast, have experienced more successful conflict resolution despite the lack of any forceful security guarantees by the international community. The termination of these civil wars can be best explained by the adherence of local actors to liberal democratic norms and institutions in response to a variety of international pressures and opportunities.
No Vacancy: The Political Geography of Immigration Control in Advanced Industrial Countries
Authors: Money Jeannette
Published: July 2002

This article examines the domestic political sources of immigration control in advanced market economy countries after World War II. Immigration control can be distinguished from the broader concept of immigration policy by its emphasis on state policies that define the permissible level of resident alien admissions. The analysis is based on the well-established fact that immigrant communities are geographically concentrated. I argue that this geographic concentration creates an uneven distribution of costs and benefits, providing a spatial context for immigration politics. In this context, net public demand for tighter immigration control increases in localities where immigrants concentrate when those areas experience higher unemployment, rapid increases in immigration, higher immigrant proportions, and more generous immigrant access to social services. Each of these conditions aggravates competition between immigrants and natives, and hence native hostility, in these communities while employer support for immigration usually diminishes. Yet national politicians may ignore changes in the demand for immigration control unless these constituencies are also able to swing a national election from one party to another. The larger and less “safe” the local constituencies, the greater their influence in this sense. Evidence from the United Kingdom between 1955 and 1981 is consistent with these propositions.
The Third Leg of the Kantian Tripod for Peace: International Organizations and Militarized Disputes, 1950–85
Authors: Russett Bruce , Oneal John R. , Davis David R.
Published: July 2002

Immanuel Kant believed that democracy, economic interdependence, and international law and organizations could establish the foundations for “perpetual peace.” Our analyses of politically relevant dyads show that each of the three elements of the Kantian peace makes a statistically significant, independent contribution to peaceful interstate relations. These benefits are evident even when the influence of other theoretically interesting factors—such as relative power, alliances, geographic contiguity, and economic growth—is held constant. Increasing the number of shared memberships in intergovernmental organizations (IGOs) by one standard deviation reduces the incidence of militarized disputes by about 23 percent from the baseline rate for a typical pair of bordering states. If both members of a dyad are democratic, conflict is 35 percent less likely than the baseline; increasing both the dyadic trade–GDP ratio and the trend in trade by a standard deviation reduces the chance of conflict by 38 percent. Together, all the Kantian variables lower the probability of a dispute by 72 percent. We check for reverse causation and find reason to believe that a feedback system is at work, with IGOs reducing conflict and low-conflict dyads joining IGOs. Democracies and interdependent states are more likely to join IGOs with one another, bringing together the three elements of a system for Kantian peace.
Economic Interests, Party, and Ideology in Early Cold War Era U.S. Foreign Policy
Authors: Fordham Benjamin O.
Published: July 2002

Although it is widely acknowledged that economic interests influence the politics of trade policy, most research on international relations treats security issues differently. Do conflicting economic interests shape political debate over foreign policy even when security issues are highly salient? To answer this question, I test a range of hypotheses about conflicting interests in the economic stakes of U.S. foreign policy during the early Cold War era. I present evidence that economic interests in their home states were closely related to senators' voting patterns on foreign policy issues. These patterns hold across economic and security issues. I also find that political parties play an important mediating role, making senators more or less receptive to various economic interests.
The Social Context in Coercive International Bargaining
Authors: Schoppa Leonard J.
Published: July 2002

Although international relations scholarship emphasizing the role of social constructs such as norms and culture has established a beachhead in the area of security studies, it has yet to take on another bastion of the rational materialist approach: studies of coercive international bargaining. Scholarship in this area, ranging from the work of Thomas Schelling to James Fearon, has long argued that bargaining outcomes reflect the material costs and benefits faced by participants in negotiations. Participants can influence outcomes, these models assume, only through tactics such as credible threats and side payments that reshape the material context of negotiations.
Where Surfaces Meet: Interviews with Stuart Kauffman, Claus Emmeche and Arantza Etxeberria
Authors: Tenhaaf Nell
Published: July 2002

This article, shaped by the author's interest in convergences between art and science, presents scientists and philosophers of science who explore that convergence. However, since their expertise lies in science, they each speak from a principally scientific point of view. In fact, a common ground that emerges among them is an overt interest in point of view, which takes the form of examining the modeler's investment in and engagement with the model. Each speaker finds some potential there, rather than limitations. Since artists tend to project their subjectivity explicitly into their work and also to be aware of how the forms or media they use influence the representations they make, the interviewees' approaches to modeling do offer points of connection between art and science.
Different Brain Mechanisms Mediate Sensitivity to Sensory Consonance and Harmonic Context: Evidence from Auditory Event-Related Brain Potentials
Authors: Regnault Pascaline , Bigand Emmanuel , Besson Mireille
Published: July 2002

The goal of this study was to analyze the time-course of sensory (bottom-up) and cognitive (top-down) processes that govern musical harmonic expectancy. Eight-chord sequences were presented to 12 musicians and 12 nonmusicians. Expectations for the last chord were manipulated both at the sensory level (i.e., the last chord was sensory consonant or dissonant) and at the cognitive level (the harmonic function of the target was varied by manipulating the harmonic context built up by the first six chords of the sequence). Changes in the harmonic function of the target chord mainly modulate the amplitude of a positive component peaking around 300 msec (P3) after target onset, reflecting top-down influences on the perceptual stages of processing. In contrast, changes in the acoustic structure of the target chord (sensory consonance) mainly modulate the amplitude of a late positive component that develops between 300 and 800 msec after target onset. Most importantly, the effects of sensory consonance and harmonic context on the event-related brain potentials associated with the target chords were found to be independent, thus suggesting that two separate processors contribute to the building up of musical expectancy.
Differential Contributions of the Left and Right Inferior Parietal Lobules to Number Processing
Authors: Chochon F. , Cohen L. , Moortele P. F. van de , Dehaene S.
Published: July 2002

We measured cerebral activation with functional magnetic resonance imaging at 3 Tesla while eight healthy volunteers performed various number processing tasks known to be dissociable in brain-lesioned patients: naming, comparing, multiplying, or subtracting single digits. The results revealed the activation of a circuit comprising bilateral intraparietal, prefrontal, and anterior cingulate components. The extension and lateralization of this circuit was modulated by task demands. The intraparietal and prefrontal activation was more important in the right hemisphere during the comparison task and in the left hemisphere during the multiplication task and was intensely bilateral during the subtraction task. Thus, partially distinct cerebral circuits with the dorsal parietal pathway underlie distinct arithmetic operations.
Learning Overcomplete Representations
Authors: Lewicki Michael S. , Sejnowski Terrence J.
Published: July 2002

In an overcomplete basis, the number of basis vectors is greater than the dimensionality of the input, and the representation of an input is not a unique combination of basis vectors. Overcomplete representations have been advocated because they have greater robustness in the presence of noise, can be sparser, and can have greater flexibility in matching structure in the data. Overcomplete codes have also been proposed as a model of some of the response properties of neurons in primary visual cortex. Previous work has focused on finding the best representation of a signal using a fixed overcomplete basis (or dictionary). We present an algorithm for learning an overcomplete basis by viewing it as probabilistic model of the observed data. We show that overcomplete bases can yield a better approximation of the underlying statistical distribution of the data and can thus lead to greater coding efficiency. This can be viewed as a generalization of the technique of independent component analysis and provides a method for Bayesian reconstruction of signals in the presence of noise and for blind source separation when there are more sources than mixtures.
A General Probability Estimation Approach for Neural Computation
Authors: Khaikine Maxim , Holthausen Klaus
Published: July 2002

We describe an analytical framework for the adaptations of neural systems that adapt its internal structure on the basis of subjective probabilities constructed by computation of randomly received input signals. A principled approach is provided with the key property that it defines a probability density model that allows studying the convergence of the adaptation process. In particular, the derived algorithm can be applied for approximation problems such as the estimation of probability densitiesor the recognition of regression functions. These approximation algorithms can be easily extended to higher-dimensional cases. Certain neural network models can be derived from our approach (e.g., topological feature maps and associative networks).
An Expectation-Maximization Approach to Nonlinear Component Analysis
Authors: Rosipal Roman , Girolami Mark
Published: July 2002

The proposal of considering nonlinear principal component analysis as a kernel eigenvalue problem has provided an extremely powerful method of extracting nonlinear features for a number of classification and regression applications. Whereas the utilization of Mercer kernels makes the problem of computing principal components in, possibly, infinite-dimensional feature spaces tractable, there are still the attendant numerical problems of diagonalizing large matrices. In this contribution, we propose an expectation-maximization approach for performing kernel principal component analysis and show this to be a computationally efficient method, especially when the number of data points is large.
On the Phase-Space Dynamics of Systems of Spiking Neurons. I: Model and Experiments
Authors: Banerjee Arunava
Published: July 2002

We investigate the phase-space dynamics of a general model of local systems of biological neurons in order to deduce the salient dynamical characteristics of such systems. In this article, we present a detailed exposition of an abstract dynamical system that models systems of biological neurons. The abstract system is based on a limited set of realistic assumptions and thus accommodates a wide range of neuronal models. Simulation results are presented for several instantiations of the abstract system, each modeling a typical neocortical column to a different degree of accuracy. The results demonstrate that the dynamics of the systems are generally consistent with that observed in neurophysiological experiments. They reveal that the qualitative behavior of the class of systems can be classified into three distinct categories: quiescence, intense periodic activity resembling a state of seizure, and sustained chaos over the range of intrinsic activity typically associated with normal operational conditions in the neocortex. We discuss basic ramifications of this result with regard to the computational nature of neocortical neuronal systems.
Information Transfer Between Rhythmically Coupled Networks: Reading the Hippocampal Phase Code
Authors: Jensen Ole
Published: July 2002

There are numerous reports on rhythmic coupling between separate brain networks. It has been proposed that this rhythmic coupling indicates exchange of information. So far, few computational models have been proposed that explore this principle and its potential computational benefits. Recent results on hippocampal place cells of the rat provide new insight; it has been shown that information about space is encoded by the firing of place cells with respect to the phase of the ongoing theta rhythm. This principle is termed phase coding and suggests that upcoming locations (predicted by the hippocampus) are encoded by cells firing late in the theta cycle, whereas current location is encoded by early firing in the theta cycle. A network reading the hippocampal output must inevitably also receive an oscillatory theta input in order to decipher the phase-coded firing patterns. In this article, I propose a simple physiologically plausible mechanism implemented as an oscillatory network that can decode the hippocampal output. By changing only the phase of the theta input to the decoder, qualitatively different information is transferred: the theta phase determines whether representations of current or upcoming locations are read by the decoder. The proposed mechanism provides a computational principle for information transfer between oscillatory networks and might generalize to brain networks beyond the hippocampal region.
A Hierarchical Dynamical Map as a Basic Frame for Cortical Mapping and Its Application to Priming
Authors: Hoshino Osamu , Inoue Satoru , Kashimori Yoshiki , Kambara Takeshi
Published: July 2002

A hierarchical dynamical map is proposed as the basic framework for sensory cortical mapping. To show how the hierarchical dynamical map works in cognitive processes, we applied it to a typical cognitive task known as priming, in which cognitive performance is facilitated as a consequence of prior experience. Prior to the priming task, the network memorizes a sensory scene containing multiple objects presented simultaneously using a hierarchical dynamical map. Each object is composed of different sensory features. The hierarchical dynamical map presented here is formed by random itinerancy among limit-cycle attractors into which these objects are encoded. Each limit-cycle attractor contains multiple point attractors into which elemental features belonging to the same object are encoded. When a feature stimulus is presented as a priming cue, the network state is changed from the itinerant state to a limit-cycle attractor relevant to the priming cue. After a short priming period, the network state reverts to the itinerant state. Under application of the test cue, consisting of some feature belonging to the object relevant to the priming cue and fragments of features belonging to others, the network state is changed to a limit-cycle attractor and finally to a point attractor relevant to the target feature. This process is considered as the identification of the target. The model consistently reproduces various observed results for priming processes such as the difference in identification time between cross-modality and within-modality priming tasks, the effect of interval between priming cue and test cue on identification time, the effect of priming duration on the time, and the effect of repetition of the same priming task on neural activity.
A Global Optimum Approach for One-Layer Neural Networks
Authors: Castillo Enrique , Fontenla-Romero Oscar , Guijarro-Berdiñas Bertha , Alonso-Betanzos Amparo
Published: July 2002

The article presents a method for learning the weights in one-layer feed-forward neural networks minimizing either the sum of squared errors or the maximum absolute error, measured in the input scale. This leads to the existence of a global optimum that can be easily obtained solving linear systems of equations or linear programming problems, using much less computational power than the one associated with the standard methods. Another version of the method allows computing a large set of estimates for the weights, providing robust, mean or median, estimates for them, and the associated standard errors, which give a good measure for the quality of the fit. Later, the standard one-layer neural network algorithms are improved by learning the neural functions instead of assuming them known. A set of examples of applications is used to illustrate the methods. Finally, a comparison with other high-performance learning algorithms shows that the proposed methods are at least 10 times faster than the fastest standard algorithm used in the comparison.
MLP in Layer-Wise Form with Applications to Weight Decay
Authors: Kärkkäinen Tommi
Published: July 2002

A simple and general calculus for the sensitivity analysis of a feedforward MLP network in a layer-wise form is presented. Based on the local optimality conditions, some consequences for the least-means-squares learning problem are stated and further discussed. Numerical experiments with formulation and comparison of different weight decay techniques are included.
Online Learning from Finite Training Sets and Robustness to Input Bias
Authors: Sollich Peter , Barber David
Published: July 2002

We analyze online gradient descent learning from finite training sets at noninfinitesimal learning rates η. Exact results are obtained for the time-dependent generalization error of a simple model system: a linear network with a large number of weights N, trained on p = αN examples. This allows us to study in detail the effects of finite training set size α on, for example, the optimal choice of learning rate η. We also compare online and offline learning, for respective optimal settings of η at given final learning time. Online learning turns out to be much more robust to input bias and actually outperforms offline learning when such bias is present; for unbiased inputs, online and offline learning perform almost equally well.
Short-Term Synaptic Plasticity and Network Behavior
Authors: Kistler Werner M. , Hemmen J. Leo van
Published: July 2002

We develop a minimal time-continuous model for use-dependent synaptic short-term plasticity that can account for both short-term depression and short-term facilitation. It is analyzed in the context of the spike response neuron model. Explicit expressions are derived for the synaptic strength as a function of previous spike arrival times. These results are then used to investigate the behavior of large networks of highly interconnected neurons in the presence of short-term synaptic plasticity. We extend previous results so as to elucidate the existence and stability of limit cycles with coherently firing neurons. After the onset of an external stimulus, we have found complex transient network behavior that manifests itself as a sequence of different modes of coherent firing until a stable limit cycle is reached.
The Relationship Between Synchronization Among Neuronal Populations and Their Mean Activity Levels
Authors: Chawla D. , Lumer E. D. , Friston K. J.
Published: July 2002

In the past decade the importance of synchronized dynamics in the brain has emerged from both empirical and theoretical perspectives. Fast dynamic synchronous interactions of an oscillatory or nonoscillatory nature may constitute a form of temporal coding that underlies feature binding and perceptual synthesis. The relationship between synchronization among neuronal populations and the population firing rates addresses two important issues: the distinction between rate coding and synchronization coding models of neuronal interactions and the degree to which empirical measurements of population activity, such as those employed by neuroimaging, are sensitive to changes in synchronization. We examined the relationship between mean population activity and synchronization using biologically plausible simulations. In this article, we focus on continuous stationary dynamics. (In a companion article, Chawla (forth-coming), we address the same issue using stimulus-evoked transients.) By manipulating parameters such as extrinsic input, intrinsic noise, synaptic efficacy, density of extrinsic connections, the voltage-sensitive nature of postsynaptic mechanisms, the number of neurons, and the laminar structure within the populations, we were able to introduce variations in both mean activity and synchronization under a variety of simulated neuronal architectures. Analyses of the simulated spike trains and local field potentials showed that in nearly every domain of the model's parameter space, mean activity and synchronization were tightly coupled. This coupling appears to be mediated by an increase in synchronous gain when effective membrane time constants are lowered by increased activity. These observations show that under the assumptions implicit in our models, rate coding and synchrony coding in neural systems with reciprocal interconnections are two perspectives on the same underlying dynamic. This suggests that in the absence of specific mechanisms decoupling changes in synchronization from firing levels, indexes of brain activity that are based purely on synaptic activity (e.g., functional magnetic resonance imaging) may also be sensitive to changes in synchronous coupling.
Training a Sigmoidal Node Is Hard
Authors: Hush Don R.
Published: July 2002

This article proves that the task of computing near-optimal weights for sigmoidal nodes under the L1 regression norm is NP-Hard. For the special case where the sigmoid is piecewise linear, we prove a slightly stronger result: that computing the optimal weights is NP-Hard. These results parallel that for the one-node pattern recognition problem—that determining the optimal weights for a threshold logic node is also intractable. Our results have important consequences for constructive algorithms that build a regression model one node at a time. It suggests that although such methods are (in principle) capable of producing efficient size representations (Barron, 1993; Jones, 1992), finding such representations may be computationally intractable. These results holds only in the deterministic sense; that is, they do not exclude the possibility that such representations may be found efficiently with high probability. In fact it motivates the use of heuristic or randomized algorithms for this problem.
The Transfer of Spatial Knowledge in Virtual Environment Training
Authors: Waller David , Hunt Earl , Knapp David
Published: July 2002

Many training applications of virtual environments (VEs) require people to be able to transfer spatial knowledge acquired in a VE to a real-world situation. Using the concept of fidelity, we examine the variables that mediate the transfer of spatial knowledge and discuss the form and development of spatial representations in VE training. We report the results of an experiment in which groups were trained in six different environments (no training, real world, map, VE desktop, VE immersive, and VE long immersive) and then were asked to apply route and configurational knowledge in a real-world maze environment. Short periods of VE training were no more effective than map training; however with sufficient exposure to the virtual training environment, VE training eventually surpassed real-world training. Robust gender differences in training effectiveness of VEs were also found.
Locomotion Mode Affects the Updating of Objects Encountered During Travel: The Contribution of Vestibular and Proprioceptive Inputs to Path Integration
Authors: Chance Sarah S. , Gaunet Florence , Beall Andrew C. , Loomis Jack M.
Published: July 2002

In two experiments, subjects traveled through virtual mazes, encountering target objects along the way. Their task was to indicate the direction to these target objects from a terminal location in the maze (from which the objects could no longer be seen). Subjects controlled their motion through the mazes using three locomotion modes. In the Walk mode, subjects walked normally in the experimental room. For each subject, body position and heading were tracked, and the tracking information was used to continuously update the visual imagery presented to the subjects on a head-mounted display. This process created the impression of immersion in the experimental maze. In the Visual Turn mode subjects moved through the environment using a joystick to control their turning. The only sensory information subjects received about rotation and translation was that provided by the computer-generated imagery. The Real Turn mode was midway between the other two modes, in that subjects physically turned in place to steer while translating in the virtual maze; thus translation through the maze was signaled only by the computer-generated imagery, whereas rotations were signaled by the imagery as well as by proprioceptive and vestibular information. The dependent measure in the experiment was the absolute error of the subject's directional estimate to each target from the terminal location. Performance in the Walk mode was significantly better than in the Visual Turn mode but other trends were not significant. A secondary finding was that the degree of motion sickness depended upon locomotion mode, with the lowest incidence occurring in the Walk mode. Both findings suggest the advisability of having subjects explore virtual environments using real rotations and translations in tasks involving spatial orientation.
A Sophisticated Manipulation Aid in a Virtual Environment using Dynamic Constraints among Object Faces
Authors: Kitamura Yoshifumi , Yee Amy , Kishino Fumio
Published: July 2002

A natural and intuitive method is proposed to help a user manipulate an object in a virtual environment. The method does not need to assign special properties to the object faces in advance and does not require special hardware. Instead, it uses only the visual constraints of motion among object faces that are dynamically selected by a real-time collision detection method while the user manipulates the object. By constraining more than two faces during the user's manipulation, the proposed method provides an efficient tool for complicated manipulation tasks. First, the method of manipulation aid is described. Then several experiments demonstrate the effectiveness of this method, particularly when the user is requested to precisely place a virtual object in a certain location. Finally, as an application of the proposed manipulation aid, an experiment is conducted to compare the performances of a task (constructing a simple toy) in a real versus a virtual environment. Results show that the distance accuracy and completion time of the virtual task with the manipulation aid is close to that of the real task.
TheCreaturesGlobal Digital Ecosystem
Authors: Cliff Dave , Grand Stephen
Published: July 2002

An artificial life entertainment-software product called Creatures was released in Europe in late 1996 and in the United States and Japan in mid-1997. When installed on a domestic computer (PC or Macintosh), each Creatures CD-ROM creates a virtual world in which autonomous software agents exist. The agents, known as “norns,” interact with the human user, with each other, and with objects in their virtual world. Each norn coordinates perception and action via its own modular recurrent neural network: Each network has Hebbian learning, plus diffuse modulation of activity via a “hormonal” system that is part of that norn's “biochemistry.” Details of each norn's neural network and biochemistry are genetically specified, and norns can breed via sexual reproduction. In the reproduction process, genetic material may be mutated and may also be subjected to “gene duplications” that enable potentially unlimited increases in complexity of the norns' design. Over 500,000 Creatures CD-ROMS have now been sold. As each installed copy of Creatures can support 5 to 10 simultaneously existing individual norns, it seems reasonable to estimate that there are up to 5 million norns existing in the “cyberspace” provided by the global Creatures user community. Continued growth of the global norn population, to figures measured in tens of millions, is quite likely. Although a commercial product, the Creatures digital ecosystem should be of interest to artificial life scientists: There are obvious parallels with Yaeger's Poly World and Ray's Net Tierra systems. This article provides a detailed discussion of the links between the artificial life literature and the technology used in Creatures and includes anecdotal discussion of the “digital naturalism” witnessed on the many independent websites maintained by Creatures enthusiasts.
AGENTS IN LATIN IMPERSONAL PASSIVES
Authors: Pieroni Silvia
Published: July 2002

The purpose of this paper is to examine the properties of the agents in Latin impersonal constructions. First of all, explicit agents do occur with impersonal passives. Furthermore, when agents are not explicitly expressed, they are predictable from the context in a number of cases. The occurrence of explicit agents as well as their predictability seems crucially dependent upon the degree of Transitivity of the clause. The verbs that occur in impersonal constructions can be graded according to a scalar notion of Transitivity along a continuum from low-intransitives to high-intransitives. My hypothesis is that the lower the degree of Transitivity of the verbs the lower the referential properties shown by the agent. Moreover, according to my analysis, the category of non-referential agents should be split into two: generic (or universal) agents should be distinguished from non-referential indefinite ones on the basis of the inclusion or non-inclusion of all the participants in the event.
Exemplary Sodomites: Chivalry and Love in Late Ming Culture
Authors: Vitiello Giovanni
Published: July 2002

This essay explores the ideological allegiances between the chivalric (xia) and the romantic (qing) in late Ming fiction and culture. Focusing on notions of friendship and love between men and their role in the formation of the late Ming romantic ideal, it also discusses the discourse on sodomy articulated in two treatises on male friendship by the Jesuit missionaries Matteo Ricci and Martino Martini, and the hypothesis of a late Ming homoerotic fashion.
SHAKESPEARE ON MONASTIC LIFE: NUNS AND FRIARS IN MEASURE FOR MEASURE
Authors: Beauregard David
Published: July 2002

Against recent claims that Shakespeare satirizes and demystifies religious life in Measure for Measure, this article maintains that Shakespeare is generally sympathetic to Franciscan nuns and friars, particularly so in this play. Indeed, Shakespeare works against the anti-fraternal tradition by reversing its conventions. Nuns and friars are represented as virtue figures, not vice figures. The secular characters are guilty of sexual irregularities, whereas the religious are chaste and work to regularize the marriages of the lay figures. The usual exposure of the sexual corruption and hypocrisy of the friar backfires on Lucio, the chief vice figure in the play. The virginal and temperate Isabella, a secular figure in Shakespeare's sources, is portrayed as a prospective novice of the Poor Clares over against the puritanical Angelo, whose hypocritical asceticism turns into lust. Angelo conducts a public shaming English Protestant style, whereas the Duke in Catholic fashion conducts a sympathetic auricular confession. Finally Isabella does not sacrifice her virginity or accept the Duke's offer of marriage, two things her counterparts in the sources invariably do. Shakespeare's reversal of anti-Catholic conventions requires us to reposition him as a Catholic rather than a conforming member of the Church of England.