bluuebunny/crossref_metadata_2025 huggingface dataset:
ISOSINGLET SCALAR MESONS BELOW 2 GeV AND THE SCALAR GLUEBALL MASS
Authors: FARIBORZ AMIR H.
Published: June 2004

A collective treatment of the I=0 scalar mesons below 2 GeV [σ(550), f0(980), f0(1370), f0(1500) and f0(1710)] in a nonlinear chiral Lagrangian framework that is constrained by the mass and the partial decay widths of the I=1/2,1 scalars [κ(900), [Formula: see text], a0(980) and a0(1450)] is presented. The sub-structure of these states in terms of two and four quark components, as well as a glueball component is explored, and its correlation with the mass of f0(1370) is studied. Consistency with the available experimental data suggests that the σ(550) is dominantly a nonstrange four-quark state, whereas the sub-structure of other I=0 states are sensitive to the input mass of f0(1370). This investigation estimates the scalar glueball mass in the range 1.47–1.64 GeV.
A SEMI EMPIRICAL APPROACH FOR ESTIMATING DISPLACEMENTS AND FUNDAMENTAL FREQUENCY OF TRANSMISSION LINE TOWERS
Authors: PRASADA RAO N. , MOHAN S. J. , LAKSHMANAN N.
Published: June 2004

Previously, it was found that the analytical deflections computed for towers using computer software are less than those from test results. The present study is aimed at deriving a relationship between the ratio of the test to theoretical deflection, and a nondimensional parameter to serve as an index for monitoring the structural displacements during testing. Currently, structural dynamic evaluation plays little or no role in the design of towers, partly due to the difficulties involved in the analysis and the relatively high cost of field testing. Using the fundamental frequency of a tower, the peak response of the tower to gusty wind and the impact force caused by conductor breakage can be evaluated. Both theoretical and experimental studies have been carried out to evaluate the natural frequencies of the towers tested at TTRS, SERC, Chennai, India. Based on these data, an equation was derived in this paper using the tower geometry and test/theoretical deflection ratios, which allows us to predict the natural frequency of the tower in a way closer to its actual value.
SEISMIC BIFURCATION FOR RESPONSE-CONTROL OF TALL BUILDING STRUCTURES
Authors: DUA RAJEEV , JAIN A. K.
Published: June 2004

The response of a structure to a seismic activity depends on the characteristics of the structural system and the seismic activity. To improve the seismic response of a structural system, it is bifurcated into two subsystems: a flexible one, catering to the primary function/occupancy of the system and a stiff one, taking care of the lateral strength requirements and housing major services of the system. Low stiffness associated with large mass in the flexible subsystem results in shifting of natural periods of the system to zones of low seismic input energy. The difference in lateral stiffness of the two subsystems results in differential response, which is utilized by placing floor-level links between the two subsystems; these links absorb and dissipate a substantial part of seismic input energy leading to a minimal structural distress. Three types of structural systems, viz. conventional system, seismically bifurcated system with rigid links (SBS-RL) and seismically bifurcated system with damping links (SBS-DL), are analyzed for various parameters. The study shows that seismic bifurcation (SB) helps in controlling the seismic response of tall building structures. The study further shows that SB technique is useful in improving seismic performance of conventionally-designed existing structures by way of seismic retrofitting.
RESONANT CURVES OF AN ELEVATED RAILWAY TO HARMONIC MOVING LOADS
Authors: CHEN YUNG-HSIANG , SHIU Z-MING
Published: June 2004

The fundamental dynamic characteristics of an elevated railway subjected to harmonic moving loads are investigated. The elevated ballast railway is analytically modeled as three different cases, with Case A indicating a simply-supported beam, Case B a two-parallel-beam system that is simply supported and inserted with a viscoelastic layer, and Case C an expansion of Case B through addition of two semi-infinite beams with viscoelastic foundation on two sides. The resonant conditions of these three cases are especially emphasized and studied in details. Finally, the resonant curves of an elevated railway to harmonic moving loads are presented, which are useful to railway engineers and may be used as preliminary design aids.
NONLINEAR ANALYSIS OF SHOCK-LOADED REINFORCED CONCRETE STRUCTURES
Authors: DHARANEEPATHY M. V. , ANANDAVALLI N.
Published: June 2004

Extensive use of reinforced concrete to build shock-protective structures calls for adequate analytical expertise to facilitate rational and safe structural designs. Although several researchers have studied these problems, there are still some uncertainties, particularly with regard to strain-rate effects. This paper presents a simplified, but accurate, numerical procedure for modeling the nonlinear behavior of reinforced concrete, using solid finite elements, which include strain-rate effects. The details of the material modeling for anisotropic concrete and isotropic steel are presented. A clamped circular plate subjected to uniformly distributed load and a clamped rectangular slab subjected to jet force are analyzed using 8-noded solid finite elements. Strain-rate effects are considered in the analyses.
A POSTERIORI ERROR ESTIMATION AND H-ADAPTIVE REFINEMENT TECHNIQUES FOR TRANSIENT DYNAMIC ANALYSIS OF STIFFENED PLATE/SHELL PANELS
Authors: PALANI G. S. , IYER NAGESH R. , RAO T. V. S. R. APPA
Published: June 2004

This paper presents a posteriori error estimation and h-adaptive refinement techniques for transient dynamic analysis of stiffened plates/shells using the finite element method (FEM). We furnish the formulation of stiffness and mass matrices for finite element (FE) models, QL9S2 and QUAD4S2 for dynamic analysis of plates/shells with arbitrarily-located concentric/eccentric stiffeners. Procedures for computing a posteriori errors for spatial and temporal errors have been presented for transient dynamic problems. An h-adaptive refinement strategy for stiffened plate/shell panels by employing QL9S2 and QUAD4S2 FE models has been discussed. An adaptive time stepping scheme, which is to be used with the time errors for quality control of the time steps, has also been presented. Numerical studies have been conducted to evaluate the efficacy of the error estimators and the adaptive mesh refinement and time stepping algorithm. The spatial error estimator for transient dynamic analysis is found to exhibit monotonic convergence at all time steps. The temporal error estimator for transient dynamic analysis in association with the adaptive time stepping is able to compute more accurate and reliable time steps to keep the time errors within the specified tolerance limits.
CONSISTENT APPROXIMATION FOR THE STRAIN ENERGY OF A 3D ELASTIC BODY ADEQUATE FOR THE STRESS STIFFENING EFFECT
Authors: YU. VETYUKOV
Published: June 2004

Starting from the fully geometrically nonlinear deformation model of a 3D elastic body, a consistent approximation for the strain energy in the vicinity of a pre-deformed state is obtained. This allows for the stress (geometric) stiffening effect to be taken into account. Additional terms arise in the strain energy approximation in comparison to the conventional approach, in which stiffening is incorporated in the form of a so-called geometric stiffness matrix. Computational costs of the new model are of the same order as that of the conventional approach. When compared to the fully geometrically nonlinear theory, the numerical analysis shows the suggested model to describe the dynamics of an elastic rotating structure better than the conventional approach. A new strategy is suggested to treat the non-constant pre-deformation, which is important for the flexible multibody simulations when angular velocities and interaction forces vary in time.
Hepatospecific effects of fructose on c-jun NH2-terminal kinase: implications for hepatic insulin resistance
Authors: Wei Yuren , Pagliassotti Michael J.
Published: June 2004

Sucrose- and fructose-enriched diets produce hepatic insulin resistance in rats independently of obesity. In humans, fructose infusion results in impaired insulin regulation of glucose production. The aim of the present study was to identify intrahepatic mediators of sucrose- and fructose-induced hepatic insulin resistance. In study 1, male rats were fed a control diet (STD, 68% of energy from corn starch, 12% from corn oil) or a sucrose-enriched diet (HSD, 68% sucrose, 12% corn oil) for 1, 2, or 5 wk. HSD produced hepatic insulin resistance at all time points. Hepatic protein tyrosine phosphatase 1B protein levels and activity were increased at 5 wk only, whereas c-jun NH2-terminal kinase (JNK) activity was increased at all time points. Normalization of JNK activity in hepatocytes isolated from HSD rats improved insulin-stimulated tyrosine phosphorylation of insulin receptor substrate (IRS) proteins and insulin suppression of glucose release. In study 2, male rats were provided STD for 1 wk and then were either fasted or fasted and refed either STD or HSD for 3 or 6 h. Rats refed HSD were characterized by increased hepatic JNK activity and phosphorylation of IRS1 on Ser307 after 6 h only. In study 3, hyperglycemic, hyperinsulinemic pancreatic clamps were performed for 3 or 6 h in the presence or absence of low or high intraportal fructose infusions. High intraportal fructose infusions, which increased portal vein fructose concentration to ∼1 mM, increased hepatic JNK activity and phosphorylation of IRS1 on Ser307 at 6 h only. These data suggest that sucrose- and fructose-induced hepatic insulin resistance are mediated, in part, via activation of JNK activity. Thus high rates of fructose metabolism in the liver appear to acutely activate stress pathways.
Expression of angiopoietins in renal epithelial and clear cell carcinoma cells: regulation by hypoxia and participation in angiogenesis
Authors: Yamakawa Midori , Liu Louis X. , Belanger Adam J. , Date Taro , Kuriyama Takayuki , Goldberg Mark A. , Cheng Seng H. , Gregory Richard J. , Jiang Canwen
Published: June 2004

The hereditary von Hippel-Lindau (VHL) syndrome predisposes sufferers to highly vascularized tumors such as renal clear cell carcinoma (RCC) and central nervous system hemangioblastoma. In RCC4 and RCC786–0 VHL− cells with VHL mutations, the protein of hypoxia-inducible factor-1α (HIF-1α) is constitutively stabilized and the mRNA levels of HIF target genes, including vascular endothelial growth factor (VEGF), are elevated. However, the expression of angiopoietins in these cells and their involvement in angiogenesis are not well known. In this study, we compared the mRNA levels of angiopoietins in human kidney proximal tubule epithelial (RPTE) and RCC4 and RCC786–0 VHL− cells. In RPTE cells, angiopoietin-4 (Ang-4) expression was selectively induced by hypoxia or by expression of a hybrid form of HIF-1α. Under normoxic conditions, the mRNA levels of Ang-4 were higher in RCC4 and RCC786–0 VHL− than RPTE cells. Angiopoietin-1 expression was detectable in RCC4 and RCC786–0 VHL− cells but not RPTE cells. In RCC786–0 VHL+ cells, which were stably transfected with a wild-type copy of VHL, the mRNA levels of VEGF and Ang-4 were suppressed and the hypoxic response was restored. We also demonstrated that stimulation of endothelial tube formation by conditioned medium harvested from RCC4 cells was inhibited by a soluble Tie-2 receptor. These results suggest that the angiopoietin/Tie-2 system may participate in the angiogenic response to hypoxia in renal tissues and in tumor angiogenesis in renal carcinoma.
Impedance Control Balances Stability With Metabolically Costly Muscle Activation
Authors: Franklin David W. , So Udell , Kawato Mitsuo , Milner Theodore E.
Published: June 2004

Humans are able to stabilize their movements in environments with unstable dynamics by selectively modifying arm impedance independently of force and torque. We further investigated adaptation to unstable dynamics to determine whether the CNS maintains a constant overall level of stability as the instability of the environmental dynamics is varied. Subjects performed reaching movements in unstable force fields of varying strength, generated by a robotic manipulator. Although the force fields disrupted the initial movements, subjects were able to adapt to the novel dynamics and learned to produce straight trajectories. After adaptation, the endpoint stiffness of the arm was measured at the midpoint of the movement. The stiffness had been selectively modified in the direction of the instability. The stiffness in the stable direction was relatively unchanged from that measured during movements in a null force field prior to exposure to the unstable force field. This impedance modification was achieved without changes in force and torque. The overall stiffness of the arm and environment in the direction of instability was adapted to the force field strength such that it remained equivalent to that of the null force field. This suggests that the CNS attempts both to maintain a minimum level of stability and minimize energy expenditure.
Knockin mice with Leu9′Ser α4-nicotinic receptors: substantia nigra dopaminergic neurons are hypersensitive to agonist and lost postnatally
Authors: Orb Sabine , Wieacker Johannes , Labarca Cesar , Fonck Carlos , Lester Henry A. , Schwarz Johannes
Published: June 2004

This study analyzes the electrophysiological cause and behavioral consequence of dopaminergic cell loss in a knockin mouse strain bearing hypersensitive nicotinic α4-receptor subunits (“L9′S mice”). Adult brains of L9′S mice show moderate loss of substantia nigra dopaminergic neurons and of striatal dopaminergic innervation. Amphetamine-stimulated locomotion is impaired, reflecting a reduction of dopamine stored in presynaptic vesicles. Recordings from dopaminergic neurons in L9′S mice show that 10 μM nicotine depolarizes cells and increases spiking rates in L9′S cells but hyperpolarizes and decreases spiking rates in wild-type (WT) cells. Thus dopaminergic neurons of L9′S mice have an excitatory response to nicotine which is qualitatively different from that of WT neurons. The cause of dopaminergic cell death is therefore probably an increased sensitivity to acetylcholine or choline of α4-containing nicotinic receptors. Hypersensitive excitatory stimulation during activation of α4-containing receptors provides the first evidence for cholinergic excitotoxicity as a cause of dopaminergic neuron death. This novel concept may be relevant to the pathophysiology of Parkinson disease.
Atherogenic Lipoprotein Particles in Atherosclerosis
Authors: Carmena Rafael , Duriez Patrick , Fruchart Jean-Charles
Published: June 2004

The importance of low-density lipoprotein (LDL) cholesterol in the development of atherosclerosis has long been recognized, and LDL cholesterol remains the primary target of therapy for the prevention of coronary heart disease. Nevertheless, increasing research attention over the past decade has been devoted to the heterogeneity of LDL particles and the atherogenicity of lipids and lipoproteins other than LDL. Particularly atherogenic forms of LDL include small, dense LDL particles and oxidized LDL. All lipoproteins that contain apolipoprotein B, such as LDL, very-low-density lipoprotein, and intermediate-density lipoprotein, tend to promote atherosclerosis; however, these particles differ in their apolipoprotein and triglyceride content. High levels of plasma triglycerides increase the risk of acute coronary events. Lipoprotein(a) is now considered an independent risk factor in both men and women. Ultimately, better understanding of the roles of these lipid particles and subfractions in the initiation and progression of atherosclerosis may affect treatment decisions.
New Risk Factors for Atherosclerosis and Patient Risk Assessment
Authors: Fruchart Jean-Charles , Nierman Melchior C. , Stroes Erik S. G. , Kastelein John J. P. , Duriez Patrick
Published: June 2004

Advances in our understanding of the ways in which the traditional cardiovascular risk factors, including standard lipid (eg, total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol) and nonlipid (eg, hypertension) risk factors, interact to initiate atherosclerosis and promote the development of cardiovascular disease have enhanced our ability to assess risk in the individual patient. In addition, the ongoing identification and understanding of so-called novel risk factors may further improve our ability to predict future risk when these are included along with the classic risk factors in assessing the global risk profile. This review briefly summarizes the evidence that some newer risk factors, including impaired fasting glucose, triglycerides and triglyceride-rich lipoprotein remnants, lipoprotein(a), homocysteine, and high-sensitivity C-reactive protein, contribute to an increased risk of coronary and cardiovascular diseases.
Role of Endothelial Dysfunction in Atherosclerosis
Authors: Davignon Jean , Ganz Peter
Published: June 2004

As the major regulator of vascular homeostasis, the endothelium exerts a number of vasoprotective effects, such as vasodilation, suppression of smooth muscle cell growth, and inhibition of inflammatory responses. Many of these effects are largely mediated by nitric oxide, the most potent endogenous vasodilator. Nitric oxide opposes the effects of endothelium-derived vasoconstrictors and inhibits oxidation of low-density lipoprotein. A defect in the production or activity of nitric oxide leads to endothelial dysfunction, signaled by impaired endothelium-dependent vasodilation. Accumulating evidence suggests that endothelial dysfunction is an early marker for atherosclerosis and can be detected before structural changes to the vessel wall are apparent on angiography or ultrasound. Many of the risk factors that predispose to atherosclerosis can also cause endothelial dysfunction, and the presence of multiple risk factors has been found to predict endothelial dysfunction. A number of clinical trials have shown that 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) improve endothelial dysfunction in patients with coronary risk factors beyond what could be attributed to their impact on plasma lipids. Studies have elucidated several possible mechanisms by which statin therapy may improve endothelial dysfunction, including upregulation of nitric oxide production or activity and reduction of oxidative stress.
Measurement of Arterial Wall Thickness as a Surrogate Marker for Atherosclerosis
Authors: de Groot Eric , Hovingh G. Kees , Wiegman Albert , Duriez Patrick , Smit Andries J. , Fruchart Jean-Charles , Kastelein John J.P.
Published: June 2004

Large observational studies and atherosclerosis regression trials of lipid-modifying pharmacotherapy have established that intima-media thickness of the carotid and femoral arteries, as measured noninvasively by B-mode ultrasound, is a valid surrogate marker for the progression of atherosclerotic disease. To exploit fully the potential of ultrasound imaging in atherosclerosis research, standardized and strictly implemented imaging protocols should be used in both observational studies and applied clinical research. This article describes such a protocol developed at the Academic Medical Center of the University of Amsterdam, the Netherlands. Results are presented from a study that estimated atherosclerosis progression from childhood into old age by measuring intima-media thickness in subjects with familial hypercholesterolemia compared with healthy controls.
Beneficial Cardiovascular Pleiotropic Effects of Statins
Authors: Davignon Jean
Published: June 2004

Pleiotropic effects of a drug are actions other than those for which the agent was specifically developed. These effects may be related or unrelated to the primary mechanism of action of the drug, and they are usually unanticipated. Pleiotropic effects may be undesirable (such as side effects or toxicity), neutral, or, as is especially the case with HMG-CoA reductase inhibitors (statins), beneficial. Pleiotropic effects of statins include improvement of endothelial dysfunction, increased nitric oxide bioavailability, antioxidant properties, inhibition of inflammatory responses, and stabilization of atherosclerotic plaques. These and several other emergent properties could act in concert with the potent low-density lipoprotein cholesterol-lowering effects of statins to exert early as well as lasting cardiovascular protective effects. Understanding the pleiotropic effects of statins is important to optimize their use in treatment and prevention of cardiovascular disease.
Statins for Stroke Prevention
Authors: Amarenco Pierre , Tonkin Andrew M.
Published: June 2004

The occurrence of stroke increases with age, particularly affecting the older elderly, a population also at higher risk for coronary heart disease (CHD). Epidemiological and observational studies have not shown a clear association between cholesterol levels and all causes of stroke. Nonetheless, large, long-term statin trials in patients with established CHD or at high risk for CHD have shown that statins decrease stroke incidence in these populations. Combined data from 9 trials including 70 070 patients indicated relative and absolute risk reductions for stroke of 21% and 0.9%, respectively, with statins. The number of strokes prevented per 1000 patients treated for 5 years in patients with CHD is 9 for statins, compared with 17.3 for antiplatelet agents. Statins have not yet been shown to reduce stroke risk in the typical general population without known CHD, nor have they been shown to prevent recurrent stroke in patients with prior stroke. Potential reasons for the effects of statins on stroke and the non–cholesterol-lowering mechanisms that may be involved are discussed. Treatment strategies based on global cardiovascular risk may be most effective. Additional studies in patients representative of the typical stroke population are needed.
Safety of Statins
Authors: Bellosta Stefano , Paoletti Rodolfo , Corsini Alberto
Published: June 2004

Statin monotherapy is generally well tolerated, with a low frequency of adverse events. The most important adverse effects associated with statins are myopathy and an asymptomatic increase in hepatic transaminases, both of which occur infrequently. Because statins are prescribed on a long-term basis, however, possible interactions with other drugs deserve particular attention, as many patients will typically receive pharmacological therapy for concomitant conditions during the course of statin treatment. This review summarizes the pharmacokinetic properties of statins and emphasizes their clinically relevant drug interactions.
Physics & reality
Authors: Einstein Albert
Published: June 2004

Editor's Note: There is probably no modern scientist as famous as Albert Einstein. Born in Germany in 1879 and educated in physics and mathematics at the Swiss Federal Polytechnic School in Zurich, he was at first unable to find a teaching post, working instead as a technical assistant in the Swiss Patent Office from 1901 until 1908.

Early in 1905, Einstein published “A New Determination of Molecular Dimensions,” a paper that earned him a Ph.D. from the University of Zurich. More papers followed, and Einstein returned to teaching, in Zurich, in Prague, and eventually in Berlin, where an appointment in 1914 to the Prussian Academy of Sciences allowed him to concentrate on research.

In November of 1919, the Royal Society of London announced that a scientific expedition had photographed a solar eclipse and completed calculations that verified the predictions that Einstein had made in a paper published three years before on the general theory of relativity. Virtually overnight, Einstein was hailed as the world's greatest genius, instantly recognizable, thanks to “his great mane of crispy, frizzled and very black hair, sprinkled with gray and rising high from a lofty brow” (as Romain Rolland described in his diary).

In the essay excerpted here, and first published in 1936, Einstein demonstrates his substantial interest in philosophy as well as science. He is pragmatic, in insisting that the only test of concepts is their usefulness in describing the physical world, yet also idealistic, in aiming for the minimum number of concepts to achieve that description.

In 1933, Einstein renounced his German citizenship and moved to the United States, where he lived until his death in 1955. A recipient of the Nobel Prize in physics in 1921, he was elected a member of the American Academy of Arts & Sciences in 1924.
The BOLD Hemodynamic Response in Healthy Aging
Authors: Aizenstein Howard J. , Clark Kristi A. , Butters Meryl A. , Cochran Jennifer , Stenger V. Andrew , Meltzer Carolyn C. , Reynolds Charles F. , Carter Cameron S.
Published: June 2004

Several previous studies have compared the blood oxygen level-dependent (BOLD) hemodynamic response (HDR) in healthy elderly subjects to the HDR in young subjects. Some studies have found a relative decreased amplitude in the elderly in the visual cortex, whereas other studies have found the elderly HDR amplitude in the visual cortex to be nearly identical to that in young subjects. A possible explanation for the different findings is that the peak voxel HDR is similar between the groups, but that the HDR in the group-averaged region-of-interest (ROI) is “washed out” by the inclusion of less significant voxels (due to a smaller extent of activation in the elderly) or by the inclusion of negative-peaking voxels. We tested this hypothesis using event-related functional magnetic resonance imaging (fMRI). While undergoing fMRI, subjects performed a simple visual and motor task, pressing with their index fingers in response to visual presentation of the word tap. Data from 18 subjects, 8 young and 10 elderly, were analyzed. For each subject, a visual and a motor ROI was selected by choosing the most significant positive voxels within the anatomically defined ROI. This individual subject approach excluded both low-significance and negative-peaking voxels. Similar peaks were found for the elderly and the young subjects in both motor and visual regions and a more sustained BOLD response was found for the elderly in both regions. Additionally, as predicted, a greater percentage of voxels with a negative HDR was found for the elderly in the visual region; this finding was also replicated in our reanalysis of an independent fMRI and aging study from the fMRI Data Center. Functional neuroimaging observations of negative HDRs in visual areas have been interpreted as the effect of unconstrained processing during rest. Our results suggest that the elderly may have more unconstrained visual processing during the rest condition in the scanner. The observation that the group differences in the BOLD response are sensitive to voxel selection (e.g., inclusion of low-significance and/or negative voxels) underscores the importance of ROI selection criteria in the interpretation of fMRI studies using elderly populations.
Derivation and Analysis of Basic Computational Operations of Thalamocortical Circuits
Authors: Rodriguez A. , Whitson J. , Granger R.
Published: June 2004

Shared anatomical and physiological features of primary, secondary, tertiary, polysensory, and associational neocortical areas are used to formulate a novel extended hypothesis of thalamocortical circuit operation. A simplified anatomically based model of topographically and nontopographically projecting (“core” and “matrix”) thalamic nuclei, and their differential connections with superficial, middle, and deep neocortical laminae, is described. Synapses in the model are activated and potentiated according to physiologically based rules. Features incorporated into the models include differential time courses of excitatory versus inhibitory postsynaptic potentials, differential axonal arborization of pyramidal cells versus interneurons, and different laminar afferent and projection patterns. Observation of the model's responses to static and time-varying inputs indicates that topographic “core” circuits operate to organize stored memories into natural similarity-based hierarchies, whereas diffuse “matrix” circuits give rise to efficient storage of time-varying input into retrievable sequence chains. Examination of these operations shows their relationships with well-studied algorithms for related functions, including categorization via hierarchical clustering, and sequential storage via hash or scatter-storage. Analysis demonstrates that the derived thalamocortical algorithms exhibit desirable efficiency, scaling, and space and time cost characteristics. Implications of the hypotheses for central issues of perceptual reaction times and memory capacity are discussed. It is conjectured that the derived functions are fundamental building blocks recurrent throughout the neo cortex, which, through combination, gives rise to powerful perceptual, motor, and cognitive mechanisms.
Reading in a Regular Orthography: An fMRI Study Investigating the Role of Visual Familiarity
Authors: Ischebeck Anja , Indefrey Peter , Usui Nobuo , Nose Izuru , Hellwig Frauke , Taira Masato
Published: June 2004

In order to separate the cognitive processes associated with phonological encoding and the use of a visual word form lexicon in reading, it is desirable to compare the processing of words presented in a visually familiar form with words in a visually unfamiliar form. Japanese Kana orthography offers this possibility. Two phonologically equivalent but visually dissimilar syllabaries allow the writing of, for example, foreign loanwords in two ways, only one of which is visually familiar. Familiarly written words, unfamiliarly written words, and pseudowords were presented in both Kana syllabaries (yielding six conditions in total) to participants during an fMRI measurement with a silent articulation task (Experiment 1) and a phonological lexical decision task (Experiment 2) using an event-related design. Consistent over two experimental tasks, the three different stimulus types (familiar, unfamiliar, and pseudoword) were found to activate selectively different brain regions previously associated with phonological encoding and word retrieval or meaning. Compatible with the predictions of the dual-route model for reading, pseudowords and visually unfamiliar words, which have to be read using phonological assembly, caused an increase in brain activity in left inferior frontal regions (BA 44/47), as compared to visually familiar words. Visually familiar and unfamiliar words were found to activate a range of areas associated with lexico-semantic processing more strongly than pseudowords, such as the left and right temporo-parietal region (BA 39/40), a region in the left middle/inferior temporal gyrus (BA 20/21), and the posterior cingulate (BA 31).
Left But Not Right Temporal Involvement in Opaque Idiom Comprehension: A Repetitive Transcranial Magnetic Stimulation Study
Authors: Oliveri Massimiliano , Romero Leonor , Papagno Costanza
Published: June 2004

It has been suggested that figurative language, which includes idioms, is controlled by the right hemisphere. We tested the right hemisphere hypothesis by using repetitive transcranial magnetic stimulation (rTMS) to transiently disrupt the function of the frontal and temporal areas of the right versus left hemisphere in a group of normal participants involved in a task of opaque idiom versus literal sentence comprehension. Forty opaque, nonambiguous idioms were selected. Fifteen young healthy participants underwent rTMS in two sessions. The experiment was run in five blocks, corresponding to the four stimulated scalp positions (left frontal and temporal and right frontal and temporal) and a baseline. Each block consisted of 16 trials—8 trials with idioms and 8 trials with literal sentences. In each trial, the subject was presented with a written sentence, which appeared on the screen for 2000 msec, followed by a pair of pictures for 2500 msec, one of which corresponded to the sentence. The alternative corresponded to the literal meaning for idioms and to a sentence differing in a detail in the case of literal sentences. The subject had to press a button corresponding to the picture matching the string. Reaction times increased following left temporal rTMS, whereas they were unaffected by right hemisphere rTMS, with no difference between idiomatic and literal sentences. Left temporal rTMS also reduced accuracy without differences between the two types of sentences. These data suggest that opaque idiom and literal sentence comprehension depends on the left temporal cortex.
Predicting Success: Patterns of Cortical Activation and Deactivation Prior to Response Inhibition
Authors: Hester Robert L. , Murphy Kevin , Foxe John J. , Foxe Deirdre M. , Javitt Daniel C. , Garavan Hugh
Published: June 2004

The present study investigated the relationships between attention and other preparatory processes prior to a response inhibition task and the processes involved in the inhibition itself. To achieve this, a mixed fMRI design was employed to identify the functional areas activated during both inhibition decision events and the block of trials following a visual cue introduced 2 to 7 sec prior (cue period). Preparing for successful performance produced increases in activation for both the cue period and the inhibition itself in the frontoparietal cortical network. Furthermore, preparation produced activation decreases in midline areas (insula and medial prefrontal) argued to be responsible for monitoring internal emotional states, and these cue period deactivations alone predicted subsequent success or failure. The results suggest that when cues are provided to signify the imminent requirement for behavioral control, successful performance results from a coordinated pattern of preparatory activation in task-relevant areas and deactivation of task-irrelevant ones.
Effects of Strategies on Mental Rotation and Hemispheric Lateralization: Neuropsychological Evidence
Authors: Tomasino Barbara , Rumiati Raffaella I.
Published: June 2004

We can predict how an object would look if we were to see it from different viewpoints by imagining its rotation. This essential human ability, called mental rotation (MR), guides individuals' actions by constantly updating their environmental consequences. It is, however, still under debate whether the way in which our brain accomplishes this operation is dete r mined by the type of stimulus or rather by a mental strategy. Here we present neuropsychological evidence sustaining the view that what matters is the type of strategy adopted in MR. Thus, independently of the type of stimulus, patients with left hemisphere lesions showed a selective deficit in MR as a consequence of their manual activity, whereas patients with right hemisphere lesions were found impaired in MR by means of a visual strategy. We conclude that MR is achieved by recruiting different strategies, implicitly triggered or prompted at will, each sustained by a unilateral brain network.
Multisensory Integration Sites Identified by Perception of Spatial Wavelet Filtered Visual Speech Gesture Information
Authors: Callan Daniel E. , Jones Jeffery A. , Munhall Kevin , Kroos Christian , Callan Akiko M. , Vatikiotis-Bateson Eric
Published: June 2004

Perception of speech is improved when presentation of the audio signal is accompanied by concordant visual speech gesture information. This enhancement is most prevalent when the audio signal is degraded. One potential means by which the brain affords perceptual enhancement is thought to be through the integration of concordant information from multiple sensory channels in a common site of convergence, multisensory integration (MSI) sites. Some studies have identified potential sites in the superior temporal gyrus/sulcus (STG/S) that are responsive to multisensory information from the auditory speech signal and visual speech movement. One limitation of these studies is that they do not control for activity resulting from attentional modulation cued by such things as visual information signaling the onsets and offsets of the acoustic speech signal, as well as activity resulting from MSI of properties of the auditory speech signal with aspects of gross visual motion that are not specific to place of articulation information. This fMRI experiment uses spatial wavelet bandpass filtered Japanese sentences presented with background multispeaker audio noise to discern brain activity reflecting MSI induced by auditory and visual correspondence of place of articulation information that controls for activity resulting from the above-mentioned factors. The experiment consists of a low-frequency (LF) filtered condition containing gross visual motion of the lips, jaw, and head without specific place of articulation information, a midfrequency (MF) filtered condition containing place of articulation information, and an unfiltered (UF) condition. Sites of MSI selectively induced by auditory and visual correspondence of place of articulation information were determined by the presence of activity for both the MF and UF conditions relative to the LF condition. Based on these criteria, sites of MSI were found predominantly in the left middle temporal gyrus (MTG), and the left STG/S (including the auditory cortex). By controlling for additional factors that could also induce greater activity resulting from visual motion information, this study identifies potential MSI sites that we believe are involved with improved speech perception intelligibility.
Consistent Chronostasis Effects across Saccade Categories Imply a Subcortical Efferent Trigger
Authors: Yarrow Kielan , Johnson Helen , Haggard Patrick , Rothwell John C.
Published: June 2004

Saccadic chronostasis refers to the subjective temporal lengthening of the first visual stimulus perceived after an eye movement, and is most commonly experienced as the “stopped clock” illusion. Other temporal illusions arising in the context of movement (e.g., “intentional binding”) appear to depend upon the volitional nature of the preceding motor act. Here we assess chronostasis across different saccade types, ranging from highly volitional (self-timed saccades, antisaccades) to highly reflexive (peripherally cued saccades, express saccades). Chronostasis was similar in magnitude across all these conditions, despite wide variations in their neural bases. The illusion must therefore be triggered by a “lowest common denominator” signal common to all the conditions tested and their respective neural circuits. Specifically, it is suggested that chronostasis is triggered by a low-level signal arising in response to efferent signals generated in the superior colliculus.
Neural Correlates of First-Person Perspective as One Constituent of Human Self-Consciousness
Authors: Vogeley K. , May M. , Ritzl A. , Falkai P. , Zilles K. , Fink G. R.
Published: June 2004

Taking the first-person perspective (1PP) centered upon one's own body as opposed to the third-person perspective (3PP), which enables us to take the viewpoint of someone else, is constitutive for human self-consciousness. At the underlying representational or cognitive level, these operations are processed in an egocentric reference frame, where locations are represented centered around another person's (3PP) or one's own perspective (1PP). To study 3PP and 1PP, both operating in egocentric frames, a virtual scene with an avatar and red balls in a room was presented from different camera viewpoints to normal volunteers (n = 11) in a functional magnetic resonance imaging experiment. The task for the subjects was to count the objects as seen either from the avatar's perspective (3PP) or one's own perspective (1PP). The scene was presented either from a ground view (GV) or an aerial view (AV) to investigate the effect of view on perspective taking. The factors perspective (3PP vs. 1PP) and view (GV vs. AV) were arranged in a two-factorial way. Reaction times were increased and percent correctness scores were decreased in 3PP as opposed to 1PP. To detect the neural mechanisms associated with perspective taking, functional magnetic resonance imaging was employed. Data were analyzed using SPM'99 in each subject and non-parametric statistics on the group level. Activations common to 3PP and 1PP (relative to baseline) were observed in a network of occipital, parietal, and prefrontal areas. Deactivations common to 3PP and 1PP (relative to baseline) were observed predominantly in mesial (i.e., parasagittal) cortical and lateral superior temporal areas bilaterally. Differential increases of neural activity were found in mesial superior parietal and right premotor cortex during 3PP (relative to 1PP), whereas differential increases during 1PP (relative to 3PP) were found in mesial prefrontal cortex, posterior cingulate cortex, and superior temporal cortex bilaterally. The data suggest that in addition to joint neural mechanisms, for example, due to visuospatial processing and decision making, 3PP and 1PP rely on differential neural processes. Mesial cortical areas are involved in decisional processes when the spatial task is solved from one's own viewpoint, whereas egocentric operations from another person's perspective differentially draw upon cortical areas known to be involved in spatial cognition.
Event-Related Potential Correlates of the Retrieval of Emotional and Nonemotional Context
Authors: Smith Adam P. R. , Dolan Raymond J. , Rugg Michael D.
Published: June 2004

In two experiments, we examined event-related potentials (ERPs) elicited in an old/new recognition memory test by emotionally neutral visual objects that, at encoding, had been associated with neutrally, negatively, or positively valenced background contexts. In Experiment 2, subjects also judged the context in which the item had been studied. In Experiment 1, “left parietal” old/new ERP effects were elicited by correctly recognized items. Items encoded in emotional contexts, but not those studied in neutral contexts, elicited additional effects early in the recording epoch over lateral temporal scalp and, later, over left temporo-frontal scalp. In Experiment 2, “left parietal” and “right frontal” ERP effects were elicited by recognized items that attracted correct source judgments. Additional effects, an early lateral temporal positivity and a late-onset, left-sided positivity, were elicited by items studied in emotionally valenced contexts and attracting correct source judgments. Together, the findings indicate that retrieval processing is influenced by the emotional valence of the context in which an item is encoded, regardless of whether contextual information is task relevant.
Shape Saliency Modulates Contextual Processing in the Human Lateral Occipital Complex
Authors: Altmann Christian F. , Deubelius Arne , Kourtzi Zoe
Published: June 2004

Visual context influences our perception of target objects in natural scenes. However, little is known about the analysis of context information and its role in shape perception in the human brain. We investigated whether the human lateral occipital complex (LOC), known to be involved in the visual analysis of shapes, also processes information about the context of shapes within cluttered scenes. We employed an fMRI adaptation paradigm in which fMRI responses are lower for two identical than for two different stimuli presented consecutively. The stimuli consisted of closed target contours defined by aligned Gabor elements embedded in a background of randomly oriented Gabors. We measured fMRI adaptation in the LOC across changes in the context of the target shapes by manipulating the position and orientation of the background elements. No adaptation was observed across context changes when the background elements were presented in the same plane as the target elements. However, adaptation was observed when the grouping of the target elements was enhanced in a bottom-up (i.e., grouping by disparity or motion) or top-down (i.e., shape priming) manner and thus the saliency of the target shape increased. These findings suggest that the LOC processes information not only about shapes, but also about their context. This processing of context information in the LOC is modulated by figure–ground segmentation and grouping processes. That is, neural populations in the LOC encode context information when relevant to the perception of target shapes, but represent salient targets independent of context changes.
Involvement of the Superior Temporal Cortex and the Occipital Cortex in Spatial Hearing: Evidence from Repetitive Transcranial Magnetic Stimulation
Authors: Lewald Jörg , Meister Ingo G. , Weidemann Jürgen , Töpper Rudolf
Published: June 2004

The processing of auditory spatial information in cortical areas of the human brain outside of the primary auditory cortex remains poorly understood. Here we investigated the role of the superior temporal gyrus (STG) and the occipital cortex (OC) in spatial hearing using repetitive transcranial magnetic stimulation (rTMS). The right STG is known to be of crucial importance for visual spatial awareness, and has been suggested to be involved in auditory spatial perception. We found that rTMS of the right STG induced a systematic error in the perception of interaural time differences (a primary cue for sound localization in the azimuthal plane). This is in accordance with the recent view, based on both neurophysio-logical data obtained in monkeys and human neuroimaging studies, that information on sound location is processed within a dorsolateral “where” stream including the caudal STG. A similar, but opposite, auditory shift was obtained after rTMS of secondary visual areas of the right OC. Processing of auditory information in the OC has previously been shown to exist only in blind persons. Thus, the latter finding provides the first evidence of an involvement of the visual cortex in spatial hearing in sighted human subjects, and suggests a close interconnection of the neural representation of auditory and visual space. Because rTMS induced systematic shifts in auditory lateralization, but not a general deterioration, we propose that rTMS of STG or OC specifically affected neuronal circuits transforming auditory spatial coordinates in order to maintain alignment with vision.
Severe hemochromatosis in a Portuguese family associated with a new mutation in the 5′-UTR of the HAMP gene
Authors: Matthes Thomas , Aguilar-Martinez Patricia , Pizzi-Bosman Loredana , Darbellay Régis , Rubbia-Brandt Laura , Giostra Emilio , Michel Martine , Ganz Tomas , Beris Photis
Published: June 2004

Juvenile hereditary hemochromatosis is a genetically heterogeneous disorder transmitted as an autosomal recessive trait. It is most often caused by mutations in the HJV gene and rarely in the HAMP gene. Hepcidin is considered to constitute a negative regulator of iron absorption, and its production is increased in inflammatory states and iron overload. We report the detection of a new mutation in the HAMP gene leading to juvenile hemochromatosis in 2 members of a Portuguese family. The mutation lies in the 5′-UTR (untranslated region) of the gene and creates a new initiation codon in the context of a Kozak sequence. We found no trace of hepcidin protein in the patients' urine, suggesting that ribosomes select the mutant initiation codon for translation. The decrease of hepcidin production would thus lead to increased iron absorption, resulting in iron deposition in parenchymal tissues. Phlebotomy therapy of the 2 patients resulted in impressive clinical improvement. (Blood. 2004;104: 2181-2183)