bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of High Pressure on Molecules
Authors: Hemley Russell J.
Published: July 2002

Recent high-pressure studies reveal a wealth of new information about the behavior of molecular materials subjected to pressures well into the multimegabar range (several hundred gigapascal), corresponding to compressions in excess of an order of magnitude. Under such conditions, bonding patterns established for molecular systems near ambient conditions change dramatically, causing profound effects on numerous physical and chemical properties and leading to the formation of new classes of materials. Representative systems are examined to illustrate key phenomena, including the evolution of structure and bonding with compression; pressure-induced phase transitions and chemical reactions; pressure-tuning of vibrational dynamics, quantum effects, and excited electronic states; and novel states of electronic and magnetic order. Examples are taken from simple elemental molecules (e.g. homonuclear diatomics), simple heteronuclear species, hydrogen-bonded systems (including H2O), simple molecular mixtures, and selected larger, more complex molecules. There are many implications that span the sciences.
RATIOMETRICSINGLE-MOLECULESTUDIES OFFREELYDIFFUSINGBIOMOLECULES
Authors: Deniz Ashok A , Laurence Ted A , Dahan Maxime , Chemla Daniel S , Schultz Peter G , Weiss Shimon
Published: July 2002

▪ Abstract  We outline recent developments in biological single-molecule fluorescence detection with particular emphasis on observations by ratiometric fluorescence resonance energy transfer (FRET) of biomolecules freely diffusing in solution. Single-molecule-diffusion methodologies were developed to minimize perturbations introduced by interactions between molecules and surfaces. Confocal microscopy is used in combination with sensitive detectors to observe bursts of photons from fluorescently labeled biomolecules as they diffuse through the focal volume. These bursts are analyzed to extract ratiometric observables such as FRET efficiency and polarization anisotropy. We describe the development of single-molecule FRET methodology and its application to the observation of the Förster distance dependence and the study of protein folding and polymer physics problems. Finally, we discuss future advances in data acquisition and analysis techniques that can provide a more complete picture of the accessible molecular information.
Potassium Channel Ontogeny
Authors: Deutsch Carol
Published: July 2002

▪ Abstract  Potassium channels are multi-subunit complexes, often composed of several polytopic membrane proteins and cytosolic proteins. The formation of these oligomeric structures, including both biogenesis and trafficking, is the subject of this review. The emphasis is on events in the endoplasmic reticulum (ER), particularly on how, where, and when K+ channel polypeptides translocate and integrate into the bilayer, oligomerize and fold to form pore-forming units, and associate with auxiliary subunits to create the mature channel complex. Questions are raised with respect to the sequence of these events, when biogenic decisions are made, models for integration of K+ channel transmembrane segments, crosstalk between the cell surface and ER, and recognition of compatible partner subunits. Also considered are determinants of subunit composition and stoichiometry, their consequence for trafficking, mechanisms for ER retention and export, and sequence motifs that direct channels to the cell surface. It is these mechanistic issues that govern the differential distributions of K+ conductances at the cell surface, and hence the electrical activity of cells and tissues underlying both the physiology and pathophysiology of an organism.
THE RED QUEEN HYPOTHESIS AND PLANT/PATHOGEN INTERACTIONS
Authors: Clay Keith , Kover Paula X.
Published: July 2002

▪ Abstract  The Red Queen Hypothesis (RQH) explains how pathogens may maintain sexual reproduction in hosts. It assumes that parasites become specialized on common host genotypes, reducing their fitness. Such frequency-dependent selection favors sexual reproduction in host populations. Necessary conditions are that resistance and virulence are genotype specific so that host genotype frequencies respond to changes in pathogen genotype frequencies, and vice versa. Empirical evidence on the genetic basis of disease, variation in resistance and virulence, and patterns of infection in sexual and asexual plants support certain features of the hypothesis. However, gene-for-gene interactions are generally not consistent with the RQH because they do not result in cycling of gene frequencies, unlike a matching allele mechanism. A conclusion of whether the RQH can explain the maintenance of sexual reproduction cannot be reached at present. Nevertheless, the RQH theory has shed light on many aspects of plant/pathogen interactions important for reducing pathogen damage in agricultural systems.
MICROBIAL POPULATION DYNAMICS ON LEAVES
Authors: Kinkel Linda L.
Published: July 2002

▪ Abstract  Microbial population dynamics on leaves in time and space are a function of immigration, emigration, growth, and death. Insight into the relative significance of each population process to the generation of specific dynamics for individual microorganisms is necessary to understanding the ecology and life history strategy of the microorganism and to developing effective control strategies. Additionally, information on the significance of within-leaf versus extra-leaf processes to the generation of phyllosphere dynamics is important to determining the range of spatial scales over which a population should be studied. Unfortunately, such information is difficult to obtain due to the lack of effective methodologies for distinguishing these processes within phyllosphere populations. Future research efforts should focus on the quantification of immigration, emigration, growth, and death relative to the population dynamics of phyllosphere microorganisms.
TYPE III PROTEIN SECRETION SYSTEMS IN PLANT AND ANIMAL PATHOGENIC BACTERIA
Authors: He Sheng Yang
Published: July 2002

▪ Abstract  Among many interesting and sophisticated mechanisms used by bacterial pathogens to subvert eukaryotic hosts is a class of specialized protein secretion systems (known as type III protein secretion systems) that deliver bacterial virulence proteins directly into the host cell. Recent studies have revealed four important features of these secretion systems. First, they are widespread among plant and animal bacterial pathogens, and mutations affecting type III protein secretion often eliminate bacterial virulence completely. Second, at least eight type III secretion components share sequence similarities with those of the flagellar assembly machinery and flagellum-like structures are associated with type III secretion, raising the possibility that these secretion systems are derived from the presumably more ancient flagellar assembly apparatus. Third, type III secretion is activated in vivo upon contact with host cells. Fourth, the type III secretion mechanism is Sec-independent and the effector proteins may possess mRNA-based targeting signals. This review highlights the similarities and differences among type III secretion systems of selected model plant and animal pathogenic bacteria.
COMMUNICATION AND OPINION
Authors: Kinder Donald R.
Published: July 2002

▪ Abstract  This chapter reviews the vast and sprawling literature that seeeks to illuminate and explain the effects of mass communication on American public opinion. Klapper's famous verdict of “minimal effects,” delivered some 40 years ago on this subject, was faithful to the evidence available to him at the time, but now seems quite mistaken. With sharp improvements in design, measurement, and analysis, and with keener understanding of human information processing, minimal effects have given way to an entire family of real effects: agenda-setting, priming, framing, and even, looking in the right places, persuasion.
Alliances: Why Write Them Down?
Authors: Morrow James D.
Published: July 2002

States formalize some relations into military alliances. A formal commitment could increase credibility by signaling an intention to come to the aid of another state or by creating commitment by altering the costs and benefits of such intervention. In this review, I lay out three considerations in a decision to intervene in a war. Signals require some costs to trasmit information, and I examine some possible costs in alliances. A state's willingness to intervene could be enhanced by audience costs for failure to honor a commitment. Neorealist arguments about alliances are flawed in asserting that security is a public good and in failing to realize that all states have both status quo and revisionist interests. This review surveys a number of smaller topics in alliances—the tradeoff between arms and allies, burden sharing, alliance management and duration, nonsecurity benefits, and domestic politics.
POLITICALCLEAVAGES ANDPOST-COMMUNISTPOLITICS
Authors: Whitefield Stephen
Published: July 2002

▪ Abstract  Considerable attention has been paid over the past decade to political cleavages in post-communist Eastern Europe. Investigators have attempted to establish whether such cleavages exist, to map their character, and to explain their formation theoretically. Research initially focused on whether communist rule had created distinctive forms of cleavage in the region as a whole, or indeed obliterated social capacity to form any structured social or ideological divisions. The results of this work, however, have tended to support a more differentiated and less sui generis understanding in which the character of cleavages varies considerably across the region. Debate has turned to accounting for the formation and variation in cleavages by reference to factors such as long-standing cultural legacies, forms of communist rule and modes of transition from it, the effects of social structure and individual social experience in the post-communist period, and the impact of institutions and party strategies.
METHODOLOGICAL ISSUES IN PSYCHOPATHOLOGY RESEARCH
Authors: Sher K. J. , Trull T. J.
Published: July 2002

▪ Abstract  We present an overview of methodological issues involved in conducting psychopathology research, including conceptual, analytic, and interpretive considerations. Research issues germane to structured diagnostic interviewing, comorbidity of mental disorders, and ascertainment and sampling are reviewed. Further, the problem of specificity (with respect to disorder, to differential deficit, and to time) is discussed. Specific issues concerning risk vs protective factors, conducting research with special populations, and the continuity of abnormal and normal functioning are highlighted. Finally, various analogue strategies (human subclinical syndromes, experimental study of “pathological” processes in normals, animal models, and computer simulations) are critiqued. Our review documents many of the impressive methodological developments that have emerged in this field, and we hope our review stimulates additional research that exploits recent methodological advances.
MODELS OF THE EMERGENCE OF LANGUAGE
Authors: MacWhinney Brian
Published: July 2002

▪ Abstract  Recent work in language acquisition has shown how linguistic form emerges from the operation of self-organizing systems. The emergentist framework emphasizes ways in which the formal structures of language emerge from the interaction of social patterns, patterns implicit in the input, and pressures arising from general aspects of the cognitive system. Emergentist models have been developed to study the acquisition of auditory and articulatory patterns during infancy and the ways in which the learning of the first words emerges from the linkage of auditory, articulatory, and conceptual systems. Neural network models have also been used to study the learning of inflectional markings and basic syntactic patterns. Using both neural network modeling and concepts from the study of dynamic systems, it is possible to analyze language learning as the integration of emergent dynamic systems.
Thought Suppression
Authors: Wenzlaff Richard M. , Wegner Daniel M.
Published: July 2002

Although thought suppression is a popular form of mental control, research has indicated that it can be counterproductive, helping assure the very state of mind one had hoped to avoid. This chapter reviews the research on suppression, which spans a wide range of domains, including emotions, memory, interpersonal processes, psychophysiological reactions, and psychopathology. The chapter considers the relevant methodological and theoretical issues and suggests directions for future research.
Acquisition of Intellectual and Perceptual-Motor Skills
Authors: Rosenbaum David A. , Carlson Richard A. , Gilmore Rick O.
Published: July 2002

▪ Abstract  Recent evidence indicates that intellectual and perceptual-motor skills are acquired in fundamentally similar ways. Transfer specificity, generativity, and the use of abstract rules and reflexlike productions are similar in the two skill domains; brain sites subserving thought processes and perceptual-motor processes are not as distinct as once thought; explicit and implicit knowledge characterize both kinds of skill; learning rates, training effects, and learning stages are remarkably similar for the two skill classes; and imagery, long thought to play a distinctive role in high-level thought, also plays a role in perceptual-motor learning and control. The conclusion that intellectual skills and perceptual-motor skills are psychologically more alike than different accords with the view that all knowledge is performatory.
Patient Outcomes Research Teams: Contribution to Outcomes and Effectiveness Research
Authors: Freund Deborah , Lave Judith , Clancy Carolyn , Hawker Gillian , Hasselblad Victor , Keller Robert , Schneiter Ellen , Wright James
Published: July 2002

▪ Abstract  This paper describes the key methodological and substantive findings of Patient Outcomes Research Teams, the first outcomes and effectiveness research centers funded by the Agency for Health Care Policy and Research. Patient Outcomes Research Teams contributed to our increased understanding of how to perform meta analysis on nontrial data, use administrative data to characterize patterns of care, develop general and disease-specific outcome measures, and disseminate important outcome information to patients and physicians to reduce practice variation. Patient Outcomes Research Teams also influenced the development of outcomes measurement in the private sector.
The Rise and Decline of Homicide—and Why
Authors: Blumstein Alfred , Rivara Frederick P. , Rosenfeld Richard
Published: July 2002

▪ Abstract  A dramatic rise in homicide in the latter half of the 1980s peaked during the 1990s and then declined at an equally dramatic rate. Such trends in homicide rates can be understood only by examining rates in specific age, sex, and racial groups. The increase primarily involved young males, especially black males, occurred first in the big cities, and was related to the sudden appearance of crack cocaine in the drug markets of the big cities around 1985. This development led to an increased need for and use of guns and was accompanied by a general diffusion of guns into the larger community. The decline in homicide since the early 1990s has been caused by changes in the drug markets, police response to gun carrying by young males, especially those under 18 years old, the economic expansion, and efforts to decrease general access to guns, as well as an increase in the prison population and a continued decline in homicide among those over age 24. The lessons learned from the recent homicide trends and the factors associated with them have important implications for public health and the criminal justice system.
Small-Community–Based Surveys
Authors: Frerichs Ralph R , Shaheen Magda A
Published: July 2002

▪ Abstract  Rapid, small surveys are routinely done in much of the developing world but are less common in the United States. We present as an example a rapid survey of immunization status and other factors in a predominantly Hispanic region in Los Angeles. The survey united county employees, students, and community volunteers, first to enumerate the eligible population and then to conduct in-person interviews. Sampling was done in two stages in a downtown region of Los Angeles. Over the course of two weekends and during clean-up the following week, volunteers and others enumerated 718 eligible children in 30 clusters (i.e. groups of blocks). At the second stage, also in two weekends with midweek clean-up, we selected by simple random sample 10 children per cluster. The parents or legal guardians of 270 children were interviewed about vaccination issues, including home presence of an immunization card. Nearly one fourth of the respondents did not have a home telephone number and thus would have been underrepresented in a telephone survey. Information from such rapid surveys is important for local program planning and evaluation.
SOCIOECONOMIC POSITION AND HEALTH: The Independent Contribution of Community Socioeconomic Context
Authors: Robert Stephanie A.
Published: July 2002

▪ Abstract  Is living in a relatively poor community bad for your health; is living in a relatively affluent community good for your health; or is it only your own socioeconomic position that matters to your health no matter where you live? This article (a) presents a conceptual model suggesting the basic pathways that may link community socioeconomic context to individual health, (b) reviews recent research that has examined whether the socioeconomic context of communities impacts the health of individual residents, over and above their own socioeconomic position, (c) discusses conceptual and methodological challenges of current research, and (d) suggests new directions for future research such as the importance of more closely examining how age, race, gender, and individual socioeconomic position may moderate the impact of community socioeconomic context on individual health and mortality.
Outside-In Signals Delivered by Matrix Metalloproteinase-1 Regulate Platelet Function
Authors: Galt Spencer W. , Lindemann Stephan , Allen Loren , Medd Donald J. , Falk Jeanne M. , McIntyre Thomas M. , Prescott Stephen M. , Kraiss Larry W. , Zimmerman Guy A. , Weyrich Andrew S.
Published: July 2002

Abstract
—

Matrix metalloproteinases (MMPs) are proteolytic enzymes that degrade extracellular matrix proteins. These enzymes are implicated in a variety of physiological and pathological events characterized by extracellular matrix remodeling. Recent studies suggest that MMPs may have a signaling capacity, but direct evidence supporting this concept is lacking. In the present study, we demonstrate that outside-in signals delivered by exogenous MMP-1 (interstitial collagenase) markedly increase the number of tyrosine-phosphorylated proteins in platelets. Active MMP-1 also targets β
3
integrins to areas of cell contact and primes platelets for aggregation. Examination of the endogenous enzyme demonstrated that activated platelets process latent MMP-1 into its active form. Neutralization of MMP-1 activity with MMP inhibitors or specific blocking antibodies markedly attenuates agonist-induced phosphorylation of intracellular proteins, movement of β
3
integrins to cell contact points, and intercellular aggregation. The finding that MMP-1 is rapidly activated in platelets and controls functional responses identifies a new role for this metalloproteinase as a signaling molecule that regulates thrombotic events.
Thrombolysis-Related Hemorrhagic Infarction
Authors: Molina Carlos A. , Alvarez-Sabín José , Montaner Joan , Abilleira Sonia , Arenillas Juan F. , Coscojuela Pilar , Romero Francisco , Codina Agusti
Published: July 2002

Background and Purpose

—

The role of early and delayed recanalization after thrombolysis in the development of hemorrhagic transformation (HT) subtypes remains uncertain. We sought to explore the association between the timing of recanalization and HT risk in patients with proximal middle cerebral artery (MCA) occlusion treated with intravenous recombinant tissue plasminogen activator (rtPA) <3 hours of stroke onset and to investigate the relationship between HT subtypes, infarct volume, and outcome.

Methods

—

Thirty-two patients with acute stroke caused by proximal MCA occlusion treated with rtPA <3 hours of symptom onset were prospectively studied. Serial transcranial Doppler examinations were performed on admission and at 6, 12, 24, and 48 hours. Presence and type of HT were assessed on CT at 36 to 48 hours. Modified Rankin scale was used to assess outcome at 3 months.

Results

—

Early and delayed recanalization was identified in 17 patients (53.1%) and 8 patients (25%), respectively. HT was detected in 14 patients (43.7%): 4 (12.5%) with hemorrhagic infarction (HI
1
), 5 (15.6%) with HI
2
, 3 (9.3%) with parenchymal hematoma (PH
1
), and 2 (6.8%) with PH
2
. Distribution of HT subtypes differed significantly (
P
=0.025), depending on the time to artery reopening. Eight of 9 (89%), 1 of 5 (20%), and 8 of 18 (44.4%) with HI
1
-HI
2
, with PH
1
-PH
2
, and without HT, respectively, recanalized in <6 hours. Delayed recanalization was observed in 1 patient with HI
1
-HI
2
(11%), 4 with PH
1
-PH
2
(80%), and 3 without HT (16.6%). Neurological improvement was significantly (
P
<0.001) more frequent in patients with HI
1
-HI
2
(88%) than in those without HT (39%). Infarct volume was significantly (
P
<0.031) lower in patients with HI
1
-HI
2
(51.4±42 cm
3
) than in patients with PH
1
-PH
2
(83.8±48 cm
3
) and those without HT (98.4±84 cm
3
,
P
=0.021). The modified Rankin scale score was significantly lower in HI
1
-HI
2
compared with PH
1
-PH
2
patients (1.9±1.1 versus 4.6±1.2,
P
<0.001) and with those without HT (1.9±1.1 versus 3.5±2.0,
P
=0.009.).

Conclusions

—

Thrombolysis-related HI (HI
1
-HI
2
) represents a marker of early successful recanalization, which leads to a reduced infarct size and improved clinical outcome.
Prognostic Importance of Leukoaraiosis in Patients With Symptomatic Internal Carotid Artery Stenosis
Authors: Streifler Jonathan Y. , Eliasziw Michael , Benavente Oscar R. , Alamowitch Sonia , Fox Allan J. , Hachinski Vladimir C. , Barnett Henry J.M.
Published: July 2002

Background and Purpose

—

Leukoaraiosis (LA) is a frequent finding on brain CT scans. This study examined patients with LA and symptomatic internal carotid artery disease.

Methods

—

Patients in the North American Symptomatic Carotid Endarterectomy Trial were evaluated for the extent of LA. Long-term prognosis and perioperative risk associated with carotid endarterectomy were assessed.

Results

—

Among 2618 patients, 493 had LA: 354 restricted and 139 widespread. Patients with LA were older, had a history of hypertension, had more hemispheric ischemic events (particularly stroke), and had small, deep brain infarcts. The 3-year risks of stroke for medically treated patients were 20.2% (no LA), 27.3% (restricted LA), and 37.2% (widespread LA) (
P
=0.01). For surgically treated patients, the risks were 14.2%, 25.4%, and 33.6%, respectively (
P
<0.001). With widespread LA, occurrence of disabling strokes doubled in medical patients and tripled in surgical patients. The 30-day perioperative risks of any stroke or death for surgical patients with 50% to 99% internal carotid artery stenosis were 5.3% (no LA), 10.6% (restricted LA), and 13.9% (widespread LA). Despite higher perioperative risk, endarterectomy reduced the absolute 3-year risk of stroke ipsilateral to the symptomatic 50% to 99% stenosed artery by 11.6% (
P
=0.46) for patients with widespread LA, 7.6% (
P
=0.39) with those with restricted LA, and 10.9% (
P
<0.001) for those with no LA.

Conclusions

—

In patients with a transient ischemic attack or nondisabling stroke associated with internal carotid artery disease, presence of LA was associated with an increased risk of any stroke and of disabling or fatal stroke. Patients with widespread LA had the worst prognosis. Despite the higher perioperative risk, endarterectomy reduced the risk of stroke.
Legalized Dispute Resolution: Interstate and Transnational
Authors: Keohane Robert O. , Moravcsik Andrew , Slaughter Anne-Marie
Published: July 2002

We identify two ideal types of international third-party dispute resolution: interstate and transnational. Under interstate dispute resolution, states closely control selection of, access to, and compliance with international courts and tribunals. Under transnational dispute resolution, by contrast, individuals and nongovernmental entities have significant influence over selection, access, and implementation. This distinction helps to explain the politics of international legalization—in particular, the initiation of cases, the tendency of courts to challenge national governments, the extent of compliance with judgments, and the long-term evolution of norms within legalized international regimes. By reducing the transaction costs of setting the process in motion and establishing new constituencies, transnational dispute resolution is more likely than interstate dispute resolution to generate a large number of cases. The types of cases brought under transnational dispute resolution lead more readily to challenges of state actions by international courts. Transnational dispute resolution tends to be associated with greater compliance with international legal judgments, particularly when autonomous domestic institutions such as the judiciary mediate between individuals and the international institutions. Overall, transnational dispute resolution enhances the prospects for long-term deepening and widening of international legalization.
Sovereignty, International Relations, and the Westphalian Myth
Authors: Osiander Andreas
Published: July 2002

The 350th anniversary of the Peace of Westphalia in 1998 was largely ignored by the discipline of international relations (IR), despite the fact that it regards that event as the beginning of the international system with which it has traditionally dealt. By contrast, there has recently been much debate about whether the “Westphalian system” is about to end. This debate necessitates, or at least implies, historical comparisons. I contend that IR, unwittingly, in fact judges current trends against the backdrop of a past that is largely imaginary, a product of the nineteenth- and twentieth-century fixation on the concept of sovereignty. I discuss how what I call the ideology of sovereignty has hampered the development of IR theory. I suggest that the historical phenomena I analyze in this article—the Thirty Years' War and the 1648 peace treaties as well as the post–1648 Holy Roman Empire and the European system in which it was embedded—may help us to gain a better understanding of contemporary international politics.
Politics at the Water's Edge: Parties, Voters, and the Use of Force Abroad
Authors: Gowa Joanne
Published: July 2002

This article examines the effects of party politics and presidential election cycles on U.S. recourse to force abroad. I analyze a game-theoretic model to generate predictions about these effects. In the unique time-consistent equilibrium outcome of the one-shot game, policy varies across political parties. In a subgame–perfect equilibrium outcome of the repeated game, the use of force is invariant to the partisan composition of government. In neither case does policy respond to the electoral cycle.

An empirical analysis supports the predictions of the repeated game. Between 1870 and 1992, U.S. recourse to force abroad responds neither to partisan politics nor to the domestic political calendar. It responds only to changes in U.S. power status and to the advent of general wars.
Design and Deforestation
Authors: Stairs David C.
Published: July 2002

Throughout their history, Americans have utilized technology to convert wilderness to civilization. Much of this development has been historically described as “progressive.” The author examines one example of this—the reduction of the Michigan pineries in the nineteenth century—in detail in an effort to reconcile design advances with our changing perceptions of wilderness. The author also discusses the development of tools and design techniques together with the evolution of the environmental movement.
On Feature Strength: Three Minimalist Approaches to Overt Movement
Authors: Lasnik Howard
Published: July 2002

Procrastinate (Chomsky 1993) favors covert movement; therefore, when movement is overt, it must have been forced to operate “early” by some special requirement, one that Chomsky codes into “strong features.” I compare Chomsky's three successive theories of strong features and argue that two ellipsis phenomena, pseudogapping and sluicing, provide evidence bearing on the nature of strong features. I argue that movement or ellipsis can rescue a derivation with a strong feature, and I conclude that PF crash is relevant either directly, as in Chomsky 1993, or indirectly, as in the theory presented in Chomsky 1995a augmented by the multiple-chain theory of pied-piping (especially as interpreted by Ochi (1998)).
Neuroanatomical Substrates of Arabic Number Processing, Numerical Comparison, and Simple Addition: A PET Study
Authors: Pesenti Mauro , Thioux Marc , Seron Xavier , Volder Anne De
Published: July 2002

Positron emission tomography was used to localize the cerebral networks specifically involved in three basic numerical processes: arabic numeral processing, numerical magnitude comparison, and retrieval of simple addition facts. Relative cerebral blood flow changes were measured while normal volunteers were resting with eyes closed, making physical judgment on nonnumerical characters or arabic digits, comparing, or adding the same digits. Processing arabic digits bilaterally produced a large nonspecific activation of occipito-parietal areas, as well as a specific activation of the right anterior insula. Comparison and simple addition fact retrieval revealed a fronto-parietal network involving mainly the left intraparietal sulcus, the superior parietal lobule and the precentral gyrus. Comparison also activated, but to a lesser extent, the right superior parietal lobe, whereas addition also activated the orbito-frontal areas and the anterior insula in the right hemisphere. Implications for current anatomo-functional models of numerical cognition are drawn.
Interconnected Large-Scale Systems for Three Fundamental Cognitive Tasks Revealed by Functional MRI
Authors: Hirsch Joy , Moreno Diana Rodriguez , Kim Karl H. S.
Published: July 2002

The specific brain areas required to execute each of three fundamental cognitive tasks-objects naming, same-different discrimination, and integer computation-are determined by whole-brain functional magnetic resonance imaging (fMRI) using a novel techinque sptimized for the isolation of neurocognitive systems. This technique (1) conjoins the activity associated with identical or nearly identical tasks performed in multiple sensory modalities (conjunction) and (2) isolates the activity conserved across multiple subjects (conservation). Cortical regions isolated by this technique are, thus, presumedassociated with cognitive functions that are both distinguished from primary sensory processes and from individual differences. The object-naming system consisted of four brain areas: left inferior frontal gyrus, Brodmann's areas (BAs) 45 and 44; left superior temporal gyrus, BA 22; and left medical frontal gyrus, BA 6. The same-different discrimination system consisted for three brain areas: right inferior parietal labule, BA 40; right precentral gyrus, BA 6; and left medial frontal gyrus, BA 6. The integer computation system consisted of five brain area: right middle frontal gyrus, BA 6; right preecentral gyrus, BA 6; left inferior parietal lobule, BA 40; left inferior frontal gyrus, BA 44; and left medial frontal gyrus, BA 6. All three neurocognitive systems shared one common cortical region, the left medial frontal gyrus, the object-naming and integer computation systems shared the left inferior frontal gyrus, and the integer computation and same-different dicrimination systems shared the right precetral gyrus. These results are consistent with connectionist models of cognitive processes where specific sets of remote brain areas are assumed to be transiently bound together as functional units to enable these functions, and further suggest a superorganization of neurocognitive systems where single brain areas serve as elemets of multiple functional systems.
Relative Shift in Activity from Medial to Lateral Frontal Cortex During Internally Versus Externally Guided Word Generation
Authors: Crosson Bruce , Sadek Joseph R. , Maron Leeza , Gökçay Didem , Mohr Cecile M. , Auerbach Edward J. , Freeman Alan J. , Leonard Christiana M. , Briggs Richard W.
Published: July 2002

Goldberg (1985) hypothesized that as language output changes from internally to externally guided production, activity shifts from supplementary motor area (SMA) to lateral premotor areas, including Broca's area. To test this hypothesis, 15 right-handed native English speakers performed three word generation tasks varying in the amount of internal guidance and a repetition task during functional magnetic resonance imaging (fMRI). Volumes of significant activity for each task versus a resting state were derived using voxel-by-voxel repeated-measures t tests (p < .001) across subjects. Changes in the size of activity volumes for left medial frontal regions (SMA and pre-SMA/BA 32) versus left lateral frontal regions (Broca's area, inferior frontal sulcus) were assessed as internal guidance of word generation decreased and external guidance increased. Comparing SMA to Broca's area, Goldberg's hypothesis was not verified. However, pre-SMA/BA 32 activity volumes decreased significantly and inferior frontal sulcus activity volumes increased significantly as word generation tasks moved from internally to externally guided.
Modulation of the Visual Word Retrieval System in Writing: A Functional MRI Study on the Japanese Orthographies
Authors: Nakamura Kimihiro , Honda Manabu , Hirano Shigeru , Oga Tatsuhide , Sawamoto Nobukatsu , Hanakawa Takashi , Inoue Hiroshi , Ito Jin , Matsuda Tetsu , Fukuyama Hidenao , Shibasaki Hiroshi
Published: July 2002

We used functional magnetic resonance imaging (fMRI) to examine whether the act of writing involves different neuro-psychological mechanisms between the two script systems of the Japanese language: kanji (ideogram) and kana (phonogram). The main experiments employed a 2 × 2 factorial design that comprised writing-to-dictation and visual mental recall for kanji and kana. For both scripts, the actual writing produced a widespread fronto-parietal activation in the left hemisphere. Especially, writing of kanji activated the left posteroinferior temporal cortex (lPITC), whereas that of kana also yielded a trend of activation in the same area. Mental recall for both scripts activated similarly the left parieto-temporal regions including the lPITC. The writing versus mental recall comparison revealed greater activations in the left sensorimotor areas and right cerebellum. The kanji versus kana comparison showed increased responses in the left prefrontal and anterior cingulate areas. Especially, the lPITC showed a significant task-by-script interaction. Two additional control tasks, repetition (REP) and semantic judgment (SJ), activated the bilateral perisylvian areas, but enhanced the lPITC response only weakly. These results suggest that writing of the ideographic and phonographic scripts, although using the largely same cortical regions, each modulates the visual word-retrieval system according to their graphic features. Furthermore, comparisons with two additional tasks indicate that the activity of the lPITC increases especially in expressive language operations regardless of sensory modalities of the input stimulus.
Conceptual Processing during the Conscious Resting State: A Functional MRI Study
Authors: Binder J. R. , Frost J. A. , Hammeke T. A. , Bellgowan P. S. F. , Rao S. M. , Cox R. W.
Published: July 2002

Localized, task-induced decreases in cerebral blood flow are a frequent finding in functional brain imaging research but remain poorly understood. One account of these phenomena postulates processes ongoing during conscious, resting states that are interrupted or inhibited by task performance. Psychological evidence suggests that conscious humans are engaged almost continuously in adaptive processes involving semantic knowledge retrieval, representation in awareness, and directed manipulation of represented knowledge for organization, problem-solving, and planning. If interruption of such “conceptual” processes accounts for task-induced deactivation, tasks that also engage these conceptual processes should not cause deactivation. Furthermore, comparisons between conceptual and nonconceptual tasks should show activation during conceptual tasks of the same brain areas that are “deactivated” relative to rest.

To test this model, functional magnetic resonance imaging data were acquired during a resting state, a perceptual task, and a semantic retrieval task. A network of left-hemisphere poly-modal cortical regions showed higher signal values during the resting state than during the perceptual task but equal values during the resting and semantic conditions. This result is consistent with the proposal that perceptual tasks interrupt processes ongoing during rest that involve many of the same brain areas engaged during semantic retrieval. As further evidence for this model, the same network of brain areas was activated in two direct comparisons between semantic and perceptual processing tasks. This same “conceptual processing” network was also identified in several previous studies that contrasted semantic and perceptual tasks or resting and active states. The model proposed here offers a unified account of these findings and may help to explain several unanticipated results from prior studies of semantic processing.
Methods for Binary Multidimensional Scaling
Authors: Rohde Douglas L. T.
Published: July 2002

Multidimensional scaling (MDS) is the process of transforming a set of points in a high-dimensional space to a lower-dimensional one while preserving the relative distances between pairs of points. Although effective methods have been developed for solving a variety of MDS problems, they mainly depend on the vectors in the lower-dimensional space having real-valued components. For some applications, the training of neural networks in particular, it is preferable or necessary to obtain vectors in a discrete, binary space. Unfortunately, MDS into a low-dimensional discrete space appears to be a significantly harder problem than MDS into a continuous space. This article introduces and analyzes several methods for performing approximately optimized binary MDS.
Energy-Efficient Coding with Discrete Stochastic Events
Authors: Schreiber Susanne , Machens Christian K. , Herz Andreas. V. M. , Laughlin Simon B.
Published: July 2002

We investigate the energy efficiency of signaling mechanisms that transfer information by means of discrete stochastic events, such as the opening or closing of an ion channel. Using a simple model for the generation of graded electrical signals by sodium and potassium channels, we find optimum numbers of channels that maximize energy efficiency. The optima depend on several factors: the relative magnitudes of the signaling cost (current flow through channels), the fixed cost of maintaining the system, the reliability of the input, additional sources of noise, and the relative costs of upstream and downstream mechanisms. We also analyze how the statistics of input signals influence energy efficiency. We find that energy-efficient signal ensembles favor a bimodal distribution of channel activations and contain only a very small fraction of large inputs when energy is scarce. We conclude that when energy use is a significant constraint, trade-offs between information transfer and energy can strongly influence the number of signaling molecules and synapses used by neurons and the manner in which these mechanisms represent information.
Multiple Model-Based Reinforcement Learning
Authors: Doya Kenji , Samejima Kazuyuki , Katagiri Ken-ichi , Kawato Mitsuo
Published: July 2002

We propose a modular reinforcement learning architecture for nonlinear, nonstationary control tasks, which we call multiple model-based reinforcement learning (MMRL). The basic idea is to decompose a complex task into multiple domains in space and time based on the predictability of the environmental dynamics. The system is composed of multiple modules, each of which consists of a state prediction model and a reinforcement learning controller. The “responsibility signal,” which is given by the softmax function of the prediction errors, is used to weight the outputs of multiple modules, as well as to gate the learning of the prediction models and the reinforcement learning controllers. We formulate MMRL for both discrete-time, finite-state case and continuous-time, continuous-state case. The performance of MMRL was demonstrated for discrete case in a nonstationary hunting task in a grid world and for continuous case in a nonlinear, nonstationary control task of swinging up a pendulum with variable physical parameters.
The Diabolo Classifier
Authors: Schwenk Holger
Published: July 2002

We present a new classification architecture based on autoassociative neural networks that are used to learn discriminant models of each class. The proposed architecture has several interesting properties with respect to other model-based classifiers like nearest-neighbors or radial basis functions: it has a low computational complexity and uses a compact distributed representation of the models. The classifier is also well suited for the incorporation of a priori knowledge by means of a problem-specific distance measure. In particular, we will show that tangent distance (Simard, Le Cun, & Denker, 1993) can be used to achieve transformation invariance during learning and recognition. We demonstrate the application of this classifier to optical character recognition, where it has achieved state-of-the-art results on several reference databases. Relations to other models, in particular those based on principal component analysis, are also discussed.
Replicator Equations, Maximal Cliques, and Graph Isomorphism
Authors: Pelillo Marcello
Published: July 2002

We present a new energy-minimization framework for the graph isomorphism problem that is based on an equivalent maximum clique formulation. The approach is centered around a fundamental result proved by Motzkin and Straus in the mid-1960s, and recently expanded in various ways, which allows us to formulate the maximum clique problem in terms of a standard quadratic program. The attractive feature of this formulation is that a clear one-to-one correspondence exists between the solutions of the quadratic program and those in the original, combinatorial problem. To solve the program we use the so-called replicator equations—a class of straightforward continuous- and discrete-time dynamical systems developed in various branches of theoretical biology. We show how, despite their inherent inability to escape from local solutions, they nevertheless provide experimental results that are competitive with those obtained using more elaborate mean-field annealing heuristics.
Re: Blau, Butler, Beckett, and the Politics of Seeming
Authors: Diamond Elin
Published: July 2002

At the core of Herbert Blau's theatre theory are meditations on appearance, repetition, bodily texts, temporality, history, and the illusory and elusive workings of power. Blau's decades of theorizing are refracted through his long experience as a theatremaker, including his production of Waiting for Godot—before an audience of San Quentin prisoners. In this essay, Diamond explores the affinities between Blau, the poststructuralists, and Beckett.
Techno-Kabbalah: The Performative Language of Magick and the Production of Occult Knowledge
Authors: Winslade J. Lawton
Published: July 2002

The X-Files, a “highly disseminated media golem” analogous to the medieval Kabbalah, signals the increasing presence in the media and the internet of occultism. Kabbalistic occultism traces a relationship between writing as an act, magic, and performance.
The Role of Global and Local Landmarks in Virtual Environment Navigation
Authors: Steck Sibylle D. , Mallot Hanspeter A.
Published: July 2002

In visual navigation, landmarks can be used in a number of different ways. In this paper, we investigate the role of global and local landmarks in virtual environment navigation. We performed an experiment in a virtual environment called “Hexatown”, consisting of a regular hexagonal grid of streets and junctions. Each junction was identified by the presence of distinct local landmarks (buildings, phone box, and so on). Additionally, compass information or a global frame of reference was provided by global landmarks (hilltop, television tower, and city skyline). According to participants' movement decisions, egomotion was simulated, and displayed on a 180 deg. projection screen. Participants learned the route back and forth between two local landmarks. In the test phase, individual junctions were approached and the participant's movement decision was recorded. We performed two experiments involving landmark changes after learning. In the first, we used conflicting cues by transposing landmarks. In the second experiment, we reduced either local or global landmark information. Results show that both local and global landmarks are used in wayfinding decisions. However, different participants rely on different strategies. In the first experiment (cue conflict) for example, some of the participants used only local landmarks while others relied exclusively on global landmarks. Other participants used local landmarks at one location and global landmarks at the other. When removing one landmark type in the second experiment, the other type could be used by almost all participants, indicating that information about the neglected landmark type was present in memory.
How VR-Based Reach-to-Grasp Experiments Can Help to Understand Movement Organization within the Human Brain
Authors: Kuhlen Torsten , Kraiss Karl-Friedrich , Steffan Roland
Published: July 2002

This paper examines the potentials of VR technology for studying the neural organization of voluntary human movements. Here, motion studies are based on experimental set-ups in which subjects and/or patients interact with virtual instead of real objects. This VR-based approach is primarily motivated by the exact controllability of computer-generated experimental conditions. Stimuli such as appearance, characteristics, and behavior of objects can be varied and presented separately or in combination. Besides general benefits such as standardization, flexibility, and efficiency, VR provides a means to realize experimental scenarios that are very difficult or even impossible to build when using real, physical set-ups. This feature is demonstrated by the example of reach-to-grasp studies with perturbation, which play an important role for the study of human motor behavior. A first VR-based experiment is described that compares motor behavior when reaching and grasping a real and a virtual cube, respectively. The results of this experiment prove that VR technology can indeed lead to new insights about how the reach-to-grasp movement is organized within the human brain.