bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel nuclear magnetic resonance techniques for the study of quadrupolar nuclei in clays and other layered materials
Authors: Rocha J . , Morais C. M. , Fernandez C.
Published: January 2004

The main developments taking place in Nuclear Magnetic Resonance Spectroscopy (NMR) of quadrupolar (spin I > 1/2) nuclei with half integer spins in solids, particularly clays and other layered materials, have been reviewed. The advent of Multiple-Quantum (MQ) Magic-Angle Spinning (MAS) NMR spectroscopy has been a step-change development to the studies of quadrupolar nuclei in solids. It is now possible to record high-resolution spectra of important nuclei, such as 11B, 17O, 23Na, 27Al and 69,71Ga, in synthetic and natural clays. Since its introduction in 1995 MQMAS NMR has evolved considerably and, at present, a range of very useful related techniques are available and have been reviewed, as has the current situation with regard to applications to clays and other layered materials.
Titanium coordination in silicate glasses investigated using O K-edge X-ray absorption spectroscopy
Authors: Henderson G. S. , Liu Xiaoyang , Fleet M. E.
Published: January 2004

A series of titanium silicate glasses along the composition joins TiO2-SiO2, TiO2-Na2SiO3, TiO2-K2SiO3 and TiO2-CaSiO3, has been examined using oxygen K-edge X-ray absorption near edge structure spectroscopy (XANES) confined to the near-surface region. Sharp pre-edge features in the spectra can be used to determine the Ti coordination in the glasses. The presence of [4]Ti is indicated by a pre-edge peak at ∼534 eV while [5]Ti is indicated by a peak at ∼533 eV. Titanium exists in all these glasses as [4]Ti and [5]Ti with no [6]Ti being present. For alkali-containing glasses the [5]Ti site becomes more prevalent with increasing TiO2. TiO2-K2SiO3 compositions contain a greater proportion of [4]Ti than comparable Na2O compositions. This is consistent with earlier Ti L-edge findings. The TEY spectra for the TiO2-CaSiO3 compositions indicate the presence of significant amounts of [5]Ti at high TiO2 contents; however, comparison of TEY (near surface) and FY (bulk sample) XANES shows that the [5]Ti is confined to the surface of the glass sample with the bulk of the glass containing [4]Ti.
Water solubility and diffusivity in olivine: its role in planetary tectonics
Authors: Regenauer-Lieb K. , Kohl T.
Published: January 2004

New constraints on the thermodynamic equation of state of water and the predicted water fugacity dependence of OH-solubility at elevated P-T conditions along with its influence on dislocation dynamics in olivine are reviewed. Water is shown to control the style of tectonics of a planetary lithosphere by switching on highly localized weak faulting instead of a broad, slow creeping flow. The transition occurs above a water concentration of 200 ppm H/Si. We argue that this changeover in style of tectonics has important implications for the mechanics of subduction and for plate tectonics in general. Efficient recycling of water is only given if the top strong part of the lithosphere can fail and be dragged down into the mantle in a steady way. Due to different starting conditions and differences in accretion through planetismals, Venus may have never have reached a water content above 200 ppm H/Si in the upper mantle while Mars would have now left the plate tectonic regime due to fast cooling.
Using neutron diffraction measurements to characterize the mechanical properties of polymineralic rocks
Authors: Schofield P. F. , Covey-Crump S. J. , Stretton I. C. , Daymond M. R. , Knight K. S. , Holloway R. F.
Published: January 2004

Conventional experiments designed to investigate the mechanical properties of polycrystalline geological materials are generally restricted to measurements of whole-rock properties. However, when comparing the measurements with theoretical models, it is frequently essential to understand how the deformation is accommodated at the grain-scale. This is particularly true for polymineralic rocks because in this case most theories express the whole-rock properties as some function of the properties of their constituent minerals, and hence the contribution which each phase makes to those properties must be measured if the theories are to be fully assessed. The penetrating nature of neutrons offers a method of addressing this problem. By performing deformation experiments in the neutron beam-line and collecting neutron diffraction patterns at different applied loads, the lattice parameters of all the mineral phases present may be determined as a function of load. The elastic strain experienced by each phase is then easily determined. Moreover, the strain in different lattice directions is also obtained. From this information a wide range of problems relevant for the characterization of the elastic and plastic deformation behaviour of polymineralic geological materials can be explored. An experimental technique for carrying out such experiments is described, and its validity is demonstrated by showing that the results obtained from deforming an elastically isotropic olivine + magnesiowüstite sample agree, to within very tight bounds, with the behaviour predicted by theory for elastically isotropic composites.
First occurrence of the rare ‘corundum + quartz’ assemblage in the high-grade zone from the Namaqualand Metamorphic Complex, South Africa: evidence for higher-P, T metamorphism?
Authors: Mouri H. , Andreoli M. A. G. , Kienast J. R. , Guiraud M. , De Waal S. A.
Published: January 2004

We report in this paper the first occurrence of the rare assemblage corundum + quartz in the high-grade metamorphic zone in the core of the Namaqualand Metamorphic Complex (NMC) (South Africa). The magnetite-bearing rocks hosting the corundum-quartz assemblage are very rare, and occur discontinuous bands a few cm wide, associated with diorite, tonalite and anorthosite within quartzfeldspar ± sillimanite ± biotite ± spinel supracrustal rocks extensively intruded by a foliated granite gneiss. The magnetite-bearing rocks are characterized by the presence of abundant crystals of magnetite together with ilmenite, spinel and large (∽1 cm in diameter) euhedral crystals of corundum both displaying a sharp contact with magnetite and quartz. However, in some micro-domains, spinel and quartz, as well as corundum and quartz, are separated by a thin corona of sillimanite with or without magnetite. These textural features suggest that the following reactions have taken place: quartz + corundum → sillimanite, and quartz + spinel + O2 → sillimanite + magnetite. These reactions are interpreted as occurring at higher, as yet unknown, P-T conditions than previously estimated for the NMC. Whether corundum and quartz were once in equilibrium is worth investigating, as it could constitute a geothermobarometric assemblage for ultra-high T granulites.
The Early Proterozoic carbonatite complex of Angico dos Dias, Bahia State, Brazil: geochemical and Sr-Nd isotopic evidence for an enriched mantle origin
Authors: Antonini P. , Comin-chiaramonti P. , Gomes C. B. , Censi P. , Riffel B. F. , Yamamoto E.
Published: January 2004

Borehole samples of carbonatites and phlogopite-pyroxenites from the Angico dos Dias (AdD) intrusive alkaline complex, State of Bahia, Brazil, have been investigated in terms of mineralogy, geochemistry and C-O-Sr-Nd isotopes. The AdD complex, of Early Proterozoic age (2 Ga), intrudes the northern side of the São Francisco Craton. Mineralogy and petrography indicate that the studied rocks only partially preserved their magmatic textural features owing to their metamorphic re-equilibration (greenschist facies). The REE contents and LREE/HREE ratios of the AdD carbonatites are very high (mean 3979±718 ppm and La/Yb = 215±23, respectively), as for most Precambrian magmatic carbonatites. The AdD carbonatites are also enriched in 18O (δ18O = 11.9 to 15.8‰), possibly due to secondary processes (e.g. metamorphism, alteration) whereas carbon isotopes are in the range of ‘primary carbonatites’ (δ13C = –5.7 to –7.1‰). Most of the initial 87Sr/86Sr and 143Nd/144Nd values of the studied carbonatites were not appreciably modified by secondary processes. Their εtSr and εtNd values (20.0 to 25 and 0.7 to –4.5, respectively) indicate enriched mantle sources very different from the ‘depleted’ ones related to many Precambrian carbonatites from North America (0.6 –2.6 Ga) and Africa (0.5 –2.0 Ga). The Early Proterozoic Sr-Nd isotopic signatures of the AdD carbonatites are similar to those of the Early Cretaceous carbonatites from the Paraná basin. The latter carbonatites show a great isotopic variability ranging from Bulk Earth to the related potassic magmatism from Asunción-Sapucai graben in the Eastern Paraguay (K-ASU magmatism: εtSr = 35 to 50 and εtNd = –12 to –20). The very similar isotopic compositions of Precambrian and post-Palaeozoic carbonatites worldwide indicate that the subcontinental mantle variability lasted for long periods of time and indicate a large-scale mantle heterogeneity.
Iron sulphides at the epithermal gold-copper deposit of Palai-Islica (Almería, SE Spain)
Authors: Carrillo Rosúa F. J. , Morales Ruano S. , Fenoll Hach-Alí P.
Published: January 2004

Au-Cu mineralization at Palai-Islica occurs as disseminations in massive silicified volcanic rocks and, more abundantly, in sulphide-bearing quartz veins. The major ore minerals in the deposit are pyrite ± chalcopyrite, sphalerite and galena and there is a great variety of accessory minerals, including Au-Ag alloys and native gold. Pyrite, the most abundant sulphide, is closely associated with gold. Seven different types of pyrite have been distinguished with a variable concentration of different trace elements. Among these, the only one free of trace elements (type IV) is related to Au-Ag alloys. Pyrite associated with these Au-Ag alloys has cubic and pentagonal dodecahedral habits, whereas pyrite with pentagonal dodecahedral habit only is from barren zones. In addition, there is no significant invisible gold in the pyrite, but there is a relatively large amount of Ag in collomorphic pyrite (up to 0.20 wt.%) or type III pyrite (up to 1.47 wt.%). Arsenic is the most abundant trace element in pyrite (up to 6.11 wt.%), present as a metastable solid solution or as a non-stoichiometric element. A variety of marcasite related to the gold levels also has a considerable amount of trace elements (As up to 1.15 wt.%, Sb up to 0.40 wt.%).
Prismatine and ferrohögbomite-2N2Sin granulite-facies Fe-oxide lenses in the Eastern Ghats Belt at Venugopalapuram, Vizianagaram district, Andhra Pradesh, India: do such lenses have a tourmaline-enriched lateritic precursor?
Authors: Grew E. S. , Rao A. T. , Raju K. K. V. S. , Hejny C. , Moore J. M. , Waters D. J. , Yates M. G. , Shearer C. K.
Published: January 2004

Fluorine-rich prismatine, (□,Fe,Mg)(Mg,Al,Fe)5Al4(Si,B,Al)5O21(OH,F), with F/(OH+F) = 0.36–0.40 and hercynite are major constituents of a Fe-Al-B-rich lens in ultrahigh-temperature granulite-facies quartz-sillimanite-hypersthene-cordierite gneisses of the Eastern Ghats belt, Andhra Pradesh, India. Hemo-ilmenite, sapphirine, magnetite, biotite and sillimanite are subordinate. Lithium, Be and B are concentrated in prismatine (140 ppm Li, 170 ppm Be, and 2.8 –3.0 wt.% B2O3). Another Fe-rich lens is dominantly magnetite, which encloses fine-grained zincian ferrohögbomite-2N2S, (Fe2+,Mg,Zn,Al)6(Al,Fe3+,Ti)16O30(OH)2, containing minor Ga2O3(0.30 –0.92 wt.%). Fe-Al-B-rich lenses with prismatine (or kornerupine) constitute a distinctive type of B-enrichment in granulite-facies rocks and have been reported from four other localities worldwide. A scenario involving a tourmalineenriched lateritic precursor affected by dehydration melting is our preferred explanation for the origin of the Fe-Al-B-rich lenses at the five localities. Whole-rock analyses and field relationships at another of these localities, Bok se Puts, Namaqualand, South Africa, are consistent with this scenario. Under granulite-facies conditions, tourmaline would have broken down to give kornerupine-prismatine (±other borosilicates) plus a sodic melt containing H2O and B. Removal of this melt depleted the rock in Na and B, but the formation of ferromagnesian borosilicate phases in the restite prevented total loss of B.
Carbonatites and lamprophyres of the Gardar Province – a ‘window’ to the sub-Gardar mantle?
Authors: Coulson I. M. , Goodenough K. M. , Pearce N. J. G. , Leng M. J.
Published: January 2004

Carbonatite magmas are considered to be ultimately derived from mantle sources, which may include lithospheric and asthenospheric reservoirs. Isotopic studies of carbonatite magmatism around the globe have typically suggested that more than one source needs to be invoked for generation of the parental melts to carbonatites, often involving the interaction of asthenosphere and lithosphere.

In the rift-related, Proterozoic Gardar Igneous Province of SW Greenland, carbonatite occurs as dykes within the Igaliko Nepheline Syenite Complex, as eruptive rocks and diatremes at Qassiarsuk, as a late plug associated with nepheline syenite at Grønnedal-Íka, and as small bodies associated with ultramafic lamprophyre dykes. The well-known cryolite deposit at Ivittuut was also rich in magmatic carbonate. The carbonatites are derived from the mantle with relatively little crustal contamination, and therefore should provide important information about the mantle sources of Gardar magmas. In particular, they are found intruded both into Archaean and Proterozoic crust, and hence provide a test for the involvement of lithospheric mantle.

A synthesis of new and previously published major and trace element, Sr, Nd, C and O isotope data for carbonatites and associated lamprophyres from the Gardar Province is presented. The majority of Gardar carbonatites and lamprophyres have consistent geochemical and isotopic signatures that are similar to those typically found in ocean island basalts. The geochemical characteristics of the two suites of magmas are similar enough to suggest that they were derived from the same mantle source. C and O isotope data are also consistent with a mantle derivation for the carbonatite magmas, and support the theory of a cogenetic origin for the carbonatites and the lamprophyres. The differences between the carbonatites and lamprophyres are considered to represent differing degrees of partial melting of a similar source.We suggest that the ultimate source of these magmas is the asthenospheric mantle, since there is no geochemical or isotopic evidence for their having been derived directly from ancient, enriched sub-continental lithospheric mantle. However, it is likely that the magmas actually formed through a two-stage process, with small-degree volatile-rich partial melts rising from the asthenospheric mantle and being ‘frozen in’ as metasomites, which were then rapidly remobilized during Gardar rifting.
Ilímaussaq ‘en miniature’: closed-system fractionation in an agpaitic dyke rock from the Gardar Province, South Greenland (contribution to the mineralogy of Ilímaussaq no. 117)
Authors: Marks M. , Markl G.
Published: January 2004

Based on petrography, mineral chemistry, and petrology, the physico-chemical evolution of an agpaitic dyke was found to be very similar to that of the neighbouring Ilímaussaq complex. Various mineral assemblages were used to reconstruct the crystallization conditions of the dyke rock for different stages during cooling. The early magmatic phenocryst assemblage is alkali feldspar + nepheline + augite + olivine + magnetite and indicates liquidus temperatures of ∼850ºC, silica activities of ∼0.5, and oxygen fugacities of FMQ –1.5 to –3. The groundmass assemblage albite + microcline + nepheline + sodalite + arfvedsonite + aegirine + aenigmatite + astrophyllite indicates lower temperatures of between 600 and 450ºC, at silica activities of 0.25, and oxygen fugacities around the FMQ buffer. Amphibole composition strongly responds to fluorite saturation and proves crystallization occurred in a system closed to oxygen. Late-stage hydrothermal conditions are indicated by the conversion of nepheline and sodalite to analcime and the growth of aegirine on arfvedsonite. These late-stage reactions are constrained to temperatures of <300°C, water activities of between 0.5 and unity, and oxygen fugacities above MH. The dyke has to be regarded as a small equivalent of the larger Ilímaussaq complex, in which identical differentiation processes proceeded at a scale very different in terms of magma volume and cooling times.
Trace-element content and partitioning in calcite, dolomite and apatite in carbonatite, Phalaborwa, South Africa
Authors: Dawson J. B. , Hinton R. W.
Published: January 2004

A carbonatite sample from Phalaborwa, South Africa, consists of apatite, magnetite and a calcitedolomite ‘perthite’ which is interpreted as being due to exsolution of dolomite from a high-Mg calcite precursor. Carbon and oxygen isotope data indicate that the carbonates are equilibrated. In situ ionmicroprobe analyses for Fe, Mn, Na, Si, Y, the REEs, Pb, Th and U give the following average concentrations (in ppm) in the sequence apatite, calcite, dolomite: Fe 98, 1680, 8190; Mn 61, 510, 615; Na 1171, 627, 125; Si 368; 1.6, 0.2; Sr 4447, 5418, 2393; Ba 37, 2189, 75; La 1245, 300, 67; Y 121, 50, 5.8; Pb 16, 5.4, 1.4; Th 20, 0.02, 0; U 2.4, 0, 0.01. The concentrations are reasonably uniform in both apatite and dolomite, but in calcite are more variable. Na, Si, Y, the REEs, Pb, Th and U partition into apatite relative to both carbonates (and, hence, the precursor carbonate); KD ap/cc for REE decreases from ∽4 for La to ∽2 for Tm. There is almost equal partitioning of Sr between apatite and calcite. During separation of dolomite from calcite, Sr and Ba partition strongly into calcite and all the other analysed elements, except Fe and Mn, also preferentially enter calcite. The REEs prefer calcite relative to dolomite, and the KD dol/cc is reasonably constant, only varying from 0.23 to 0.17. Sr, Ba and Pb in the carbonates, and their partitioning between the calcite and dolomite, differ from other carbonatite carbonates reported in the literature.
Pb-bearing hollandite-type titanates: A first natural occurrence and reconnaissance synthesis study
Authors: Reguir E. P. , Chakhmouradian A. R. , Mitchell R. H.
Published: January 2004

Some samples of hollandite-type titanates from the Murun alkaline complex (Yakutia, Russia) contain appreciable amounts of Pb (up to 12.5 wt.% PbO). These titanates occur in a pegmatitic K-feldsparaegirine rock containing subordinate K-rich batisite, titanite, wadeite and other minerals. The Pb-bearing crystals coexist with hollandite-type phases devoid of detectable Pb and zoned from a Kdominant (priderite) core to a Ba-dominant (henrymeyerite) rim. Recalculation of the microprobe analyses on the stoichiometric basis indicates that most of the Fe occurs in this mineral in trivalent form, suggesting the existence of a solid solution between the Ba(Ti6Fe)O16, K2(Ti6Fe)O16 and Pb(Ti6Fe)O16 end-members. The maximum proportion of the latter end-member in the Murun titanates is ∽45 mol.%. The Ba-free compositions [Pb1.0–1.3(Ti,Fe)8O16] and intermediate members of the (Ba1–xPbx)(Ti6Fe)O16 series were synthesized at 1050 –1100ºC. The synthesis products comprise tetragonal hollandites of various stoichiometry intermixed with rutile, a pseudobrookite-type phase and (for the Ba-free compositions) minor macedonite. Electron microprobe analyses of the hollandites indicate that there is a continuous series of compositions between the two hexatitanate end-members, Ba(Ti6Fe)O16 and Pb(Ti6Fe)O16. The crystal structure of one intermediate member was refined by the Rietveld method in space group I4/m, and found to differ from the hollandite archetype (i.e. Pb-bearing Ba manganate) in that Pb is preferentially partitioned into the 2b tunnel site at (0,0,½), whereas Ba is partitioned into the larger 4e site at (0,0,∽0.8).
Synapse‐Specific Gene Expression at the Neuromuscular Junction
Authors: MÉJAT ALEXANDRE , RAVEL‐CHAPUIS AYMERIC , VANDROMME MARIE , SCHAEFFER LAURENT
Published: January 2004

Abstract: Agrin is the key neural factor that controls muscle postsynaptic differentiation, including the induction of synapse‐specific transcription via neuregulins. In 1995, the promoter element responsible for the targeting of AChR δ and ε gene transcription to the skeletal muscle subsynaptic area was identified. This element, named N‐box, recruits the Ets‐related transcription factor GABP to AChR δ and ε promoters, and both the N‐box and GABP are required to obtain transcriptional stimulation by neuregulins. The physiological importance of the N‐box has been definitively established with the discovery of myasthenic families carrying single‐point mutations in the N‐box of the AChR ε gene promoter and showing reduced levels of AChR ε subunit expression. The control of synapse‐specific transcription by agrin and neuregulins through the N‐box and GABP is not restricted to the case of AChR genes. The same regulation holds true for the ACh esterase and utrophin genes, thus showing that nerve‐induced transcriptional activation of several synapse‐specific genes is triggered by a common mechanism involving agrin, neuregulins, and ultimately the N‐box and Ets‐related transcription factors.
Regulation of Nicotinic Acetylcholine Receptor Assembly
Authors: WANAMAKER CHRISTIAN P. , CHRISTIANSON JOHN C. , GREEN WILLIAM N.
Published: January 2004

Abstract: The four muscle‐type nicotinic acetylcholine receptor (AChR) subunits, α, β, γ, and δ, assemble into functional α2βγδ pentamers in the endoplasmic reticulum (ER) through a series of interdependent folding and oligomerization events. The first stable assembly intermediate is a trimer composed of α, β, and γ subunits. The formation of αβγ trimers initiates a series of subunit folding and processing events that allow addition of δ subunits to form αβγδ tetramers. Subunit folding and processing continue with formation of the ligand‐binding sites on the α subunit of αβγδ tetramers and the second α subunit added to assemble α2βγδ pentamers. AChR assembly is inefficient. Only 20–30% of synthesized subunits assemble into mature receptors in the ER, while the remaining unassembled subunits are degraded. However, the efficiency of subunit assembly can be regulated under certain conditions leading to higher AChR expression. Increased intracellular cAMP levels cause a 2‐ to 3‐fold increase in AChR assembly efficiency and a comparable increase in surface expression. Additionally, block of ubiquitin‐proteasome degradation appears to enhance AChR assembly and expression. Thus, the regulation of AChR assembly through posttranslational mechanisms is a potential therapeutic target for increasing AChR expression in diseases in which expression is compromised.
A New Model Linking Intrathymic Acetylcholine Receptor Expression and the Pathogenesis of Myasthenia Gravis
Authors: LEVINSON ARNOLD I. , ZHENG YI , GAULTON GLEN , MOORE JONNI , PLETCHER C. HANK , SONG DECHENG , WHEATLEY LISA M.
Published: January 2004

Abstract: The thymus is thought to play an important role in the pathogenesis of myasthenia gravis (MG), an autoimmune disease characterized by skeletal muscle weakness. However, its role remains a mystery. The studies described represent our efforts to determine how intrathymic expression of the neuromuscular type of acetylcholine receptors (nAChRs) is involved in the immunopathogenesis of MG. We review our work characterizing the expression of the alpha subunit of nAChR (nAChRα) in the thymus and advance a new hypothesis that examines the intrathymic expression of this autoantigen in disease pathogenesis.
Antibodies in Myasthenia Gravis and Related Disorders
Authors: VINCENT ANGELA , McCONVILLE JOHN , FARRUGIA MARIA ELENA , BOWEN JOHN , PLESTED PAUL , TANG TERESA , EVOLI AMELIA , MATTHEWS IAN , SIMS GARY , DALTON PAOLA , JACOBSON LESLIE , POLIZZI AGATA , BLAES FRANS , LANG BETHAN , BEESON DAVID , WILLCOX NICK , NEWSOM‐DAVIS JOHN , HOCH WERNER
Published: January 2004

Abstract: Acetylcholine receptor (AChR) antibodies are present in around 85% of patients with myasthenia gravis (MG) as measured by the conventional radioimmunoprecipitation assay. Antibodies that block the fetal form of the AChR are occasionally present in mothers who develop MG after pregnancy, especially in those whose babies are born with arthrogryposis multiplex congenita. The antibodies cross the placenta and block neuromuscular transmission, leading to joint deformities and often stillbirth. In these mothers, antibodies made in the thymus are mainly specific for fetal AChR and show restricted germline origins, suggesting a highly mutated clonal response; subsequent spread to involve adult AChR could explain development of maternal MG in those cases who first present after pregnancy. In the 15% of “seronegative” MG patients without AChR antibodies (SNMG), there are serum factors that increase AChR phosphorylation and reduce AChR function, probably acting via a different membrane receptor. These factors are not IgG and could be IgM or even non‐Ig serum proteins. In a proportion of SNMG patients, however, IgG antibodies to the muscle‐specific kinase, MuSK, are present. These antibodies are not found in AChR antibody‐positive MG and are predominantly IgG4. MuSK antibody positivity appears to be associated with more severe bulbar disease that can be difficult to treat effectively.
The Epidemiology of Myasthenia Gravis
Authors: PHILLIPS LAWRENCE H.
Published: January 2004

Abstract: Population‐based studies of the epidemiology of myasthenia gravis (MG) have been conducted for over 50 years. Over that time, there has been a clear trend towards an increase in the reported prevalence of the disease. In recent years, there has also been an interest in determining a reasonably accurate estimate of the number of MG patients in the United States. Current estimates place the prevalence at a high value of about 20 per 100,000. The year 2000 U.S. population estimate is slightly less than 280 million. A crude estimate of the number of MG patients derived from the population estimate and the reported prevalence from selected populations indicates that there are between 53,000 and 59,900 patients in the United States at this time. The age and ethnic distributions in the United States are evolving from those that were present when the majority of the population‐based studies were done, and the distribution of severity of the disease may also have changed. Future studies of the epidemiology of MG should take these factors into account, and further research into the economic and quality‐of‐life impact of the disease in the population is needed.
Standards of Measurements in Myasthenia Gravis
Authors: BAROHN RICHARD J.
Published: January 2004

Abstract: In 1997, the Medical Scientific Advisory Board of the Myasthenia Gravis Foundation of America formed a Task Force to develop classification and outcome measures for myasthenia gravis (MG). The goal of the Task Force was to achieve uniformity in recording and reporting clinical trials and outcomes research. The Task Force met frequently over a three‐year period, obtained input from national and international experts, and produced a consensus document on recommendations for MG clinical research standards. In this article, the essential elements of the Task Force's recommendations will be summarized. In addition, several other MG measurement tools that are in various stages of development are mentioned.
Self‐Representation in Nervous Systems
Authors: CHURCHLAND PATRICIA S.
Published: January 2004

Abstract:The brain's earliest self‐representational capacities arose as evolution found neural network solutions for coordinating and regulating inner‐body signals, thereby improving behavioral strategies. Additional flexibility in organizing coherent behavioral options emerges from neural models that represent some of the brain's inner states as states of its body, while representing other signals as perceptions of the external world. Brains manipulate inner models to predict the distinct consequences in the external world of distinct behavioral options. The self thus turns out to be identifiable not with a nonphysical soul, but rather with a set of representational capacities of the physical brain.
Knowing about Knowing
Authors: HAUSER MARC D.
Published: January 2004

Abstract: Studies of human patients reveal dissociations between perception and action; some patients have implicit knowledge for a given domain, but can't access this knowledge for action. Studies of human infant development reveal a similar dissociation, suggesting that the neural systems connecting action with perception are not formed until the early preschool years, perhaps later. These connections are fundamental to our knowledge, to what we know about what we know. In this chapter I discuss the evolution of this knowledge, and argue that the dissociations seen in patients and in infant development are also seen in normal adult nonhuman primates, especially in the domain of folk physics. This suggests that for some domains of knowledge, animals don't know what they know. The disconnect between perception and action leads, in some cases, to perseverative errors. These errors, in turn, provide the signature of a highly encapsulated, modular system.
The Seven Sins of Memory
Authors: SCHACTER DANIEL L. , CHIAO JOAN Y. , MITCHELL JASON P.
Published: January 2004

Abstract: We examine the relation between memory and self by considering errors of memory. We draw on the idea that memory's imperfections can be classified into seven basic categories or “sins.” Three of the sins concern different types of forgetting (transience, absent‐mindedness, and blocking), three concern different types of distortion (misattribution, suggestibility, and bias), and one concerns intrusive memories (persistence). We focus in particular on two of the distortion‐related sins, misattribution and bias. By describing cognitive, neuropsychological, and neuroimaging studies that illuminate these memory sins, we consider how they might bear on the relation between memory and self.
Musicogenic Seizures
Authors: AVANZINI GIULIANO
Published: January 2004

Abstract: Eighty‐seven reports of patients with seizures induced by listening and/or playing music and one personal observation are reviewed. Music‐induced (or musicogenic) seizures are currently classified among the reflex seizures precipitated by complex stimuli. According to the available information, they are defined as focal seizures due to a discharge involving lateral and mesial temporal and orbitofrontal areas. The specific musical component responsible for seizure precipitation is still undetermined. An important role is attributed to the emotional aspect of music. The existence of this rare disorder should be borne in mind by neurologists, who should also be aware of the existing musical test batteries that may help in understanding better the nature of triggering mechanisms responsible for this unique pathological condition. The implementations of the results of ongoing investigations on brain processing of musical information will advance our understanding of the mechanisms responsible for the transition from interictal to ictal phases of epilepsy.
Music as a Biocultural Phenomenon
Authors: CROSS IAN
Published: January 2004

Abstract:There is a need to clarify the domain of music as an object of cognitive and neuroscientific research. This paper explores some ramifications of an inclusive delineation of the domain of music for such research.
Specialization of the Specialized: Electrophysiological Investigations in Professional Musicians
Authors: MÜNTE THOMAS F. , NAGER WIDO , BEISS TILLA , SCHROEDER CHRISTINE , ALTENMÜLLER ECKART
Published: January 2004

Abstract: Several event‐related brain potential (ERP) studies examining the processing of auditory stimuli by professional musicians compared with non‐musicians are reviewed. In the first study, musicians (string players) and non‐musicians attended to one of two streams of auditory stimuli characterized by a specific pitch. Musicians showed a prolonged ERP attention effect, the late portion of which was more frontally distributed than was that of the non‐musicians. In the second study, we investigated auditory spatial processing in conductors, pianists, and nonmusicians. Only the conductors showed behavioral selectivity of sound sources located in the peripheral auditory space. In addition, this group showed a negative/positive mismatch response for deviant stimuli occurring outside the focus of spatial attention. Finally, a group of drummers was compared to woodwind players and nonmusicians in a passive listening task. A real continuous drum sequence was manipulated so that some beats were anticipated by 80 ms. The drummers showed a mismatch response not only for the anticipated beats but also for the subsequent beats, suggesting a more complex representation of the temporal aspects stimulus sequence in this subject group. Together, these studies suggest qualitative differences of the neural correlates of auditory processing between musicians and non‐musicians. Moreover, these differences appear to be shaped by the specific training of a musician.
Neuropsychological Studies of Musical Timbre
Authors: SAMSON SÉVERINE
Published: January 2004

Abstract: Musical timbre is a multidimensional property of sound that allows one to distinguish musical instruments. In this paper, studies that explore the cerebral substrate underlying the processing of musical timbre are discussed. Perceptual asymmetries measured in normal participants, deficits of musical timbre perception obtained in brain‐damaged patients, as well as results obtained with various neuroimaging methods are reviewed. The findings obtained in all of these studies generally support the predominant involvement of right temporal lobe areas, and more specifically of its anterior part, in processing spectral and temporal envelopes of musical timbre. However, controversies still exist about the contribution of the left temporal lobe in timbre perception. The necessity of comparing data obtained with different perceptual paradigms (same‐different discrimination and similarity judgment) and various types of stimuli (single tones and melodies) was emphasized by reporting lesion studies carried out in patients with unilateral temporal lobe lesions. The few neuroimaging studies published in this domain provided additional and complementary findings. Unlike lesion studies that allow us to infer the cerebral structures that are essential for timbre perception, the latter investigations implicate a more distributed neural network in timbre processing that extends along the superior temporal gyrus to include not only anterior but also posterior temporal regions and possibly frontal areas as well.
Cortical Correlates of Acquired Deafness to Dissonance
Authors: BRATTICO ELVIRA , TERVANIEMI MARI , VALIMAKI VESA , VAN ZUIJEN TITIA , PERETZ ISABELLE
Published: January 2004

Abstract: Patient I.R., who had bilateral lesions in the auditory cortex but intact hearing, did not distinguish dissonant from consonant musical excerpts in behavioral testing. We additionally found that the electrical brain responses did not differentiate musical intervals in terms of their dissonance/consonance, consistent with the idea that this phenomenon depends on the integrity of cortical functions.
Evoked Potentials of the Human Auditory Cortex: Sensitive to the Harmonic Series?
Authors: JONES STEVE J.
Published: January 2004

Abstract: Cortically generated auditory evoked potentials (N1 and P2) were recorded to frequency changes of harmonic and inharmonic complex tones comprising four sinusoidal components. The responses obtained when the frequencies suddenly became stationary after a period of 16/s changes were significantly shorter in latency when the frequencies were harmonically related, possibly implying a process of periodicity detection.
Chemically Defined Parallel Pathways in the Monkey Auditory System
Authors: JONES EDWARD G.
Published: January 2004

Abstract:The pathways ascending through the brain stem to the medial geniculate complex of the thalamus can be distinguished by immunostaining for the calcium binding proteins parvalbumin and calbindin and by the properties of the neurons in the subdivisions of the medial geniculate complex in which they terminate. The parvalbumin pathway, ascending from the central nucleus of the inferior colliculus, is the more direct and terminates in the ventral nucleus. The calbindin pathway is more diffuse in its origins and terminates in the dorsal and medial nuclei. Ventral nucleus neurons are sharply tuned, tonotopically organized and consistent in their responses. They project to core areas of the auditory cortex characterized by high parvalbumin immunoreactivity and by similar neuronal properties. Neurons in the dorsal and medial nuclei are not frequency specific or tonotopic and are labile in their responses. They project more diffusely to belt areas of the auditory cortex in which parvalbumin immunoreactivity is reduced and in which neuronal responses are less specific than in the core. The belt areas are the origins of streams of corticocortical connections leading into the temporal, parietal, and frontal lobes. These routes can be differentially engaged in functional imaging studies of monkeys responding to biologically significant sounds.
Musical Skills and Neural Functions
Authors: BENTIVOGLIO MARINA
Published: January 2004

Abstract: An overview of the history of debates on the correlation of musical skills with neurological functions in health and disease is presented. Selected biographical sketches of composers (Hildegard von Bingen, Mozart, Donizetti, Mussorgsky, and Ravel), whose neurological disease may have influenced musical creativity, are discussed. The search for information on the localization of skills in the brains of musicians is reviewed. The relation of mental ability to brain structure is a prominent theme in the history of neuroscience, and the effort to localize musical skills dates back to the excesses of phrenology in the early nineteenth century. The phrenological tables included an “organ of music” among the sites subserving intellectual capabilities, mapped on the basis of palpation of the head bumps. Since the second half of the nineteenth century, when the study of brain physiology, anatomy, and pathology had a remarkable development and impact on the neurosciences, structural features of the brain, particularly the cerebral cortex, of individuals with peculiar talents, including musical skills, have been examined to search for clues on the localization of mental phenomena. These studies, which continued in the twentieth century, are currently difficult to validate in view of the rigor imposed by current scientific standards. However, the issue of localization of functions in the musical brain is still debated and is now at the forefront of the neurosciences, exploiting especially functional neuroimaging. The historical overview of these problems is certainly exemplary of progress of knowledge, but also warns against excessive “localizationist” efforts.
Brain Processing of Meter and Rhythm in Music
Authors: KUCK HELEN , GROSSBACH MICHAEL , BANGERT MARC , ALTENMÜLLER ECKART
Published: January 2004

Abstract: To determine cortical structures involved in “global” meter and “local” rhythm processing, slow brain potentials (DC potentials) were recorded from the scalp of 18 musically trained subjects while listening to pairs of monophonic sequences with both metric structure and rhythmic variations. The second sequence could be either identical to or different from the first one. Differences were either of a metric or a rhythmic nature. The subjects' task was to judge whether the sequences were identical or not. During processing of the auditory tasks, brain activation patterns along with the subjects' performance were assessed using 32‐channel DC electroencephalography. Data were statistically analyzed using MANOVA. Processing of both meter and rhythm produced sustained cortical activation over bilateral frontal and temporal brain regions. A shift towards right hemispheric activation was pronounced during presentation of the second stimulus. Processing of rhythmic differences yielded a more centroparietal activation compared to metric processing. These results do not support Lerdhal and Jackendoff's two‐component model, predicting a dissociation of left hemispheric rhythm and right hemispheric meter processing. We suggest that the uniform right temporofrontal predominance reflects auditory working memory and a pattern recognition module, which participates in both rhythm and meter processing. More pronounced parietal activation during rhythm processing may be related to switching of task‐solving strategies towards mental imagination of the score.
Perceptual and Structural Implications of “Virtual” Music on the Web
Authors: DUCKWORTH WILLIAM
Published: January 2004

Abstract: The development of Cathedral, one of the first interactive works of music and art on the World Wide Web; the development of new virtual instruments, such as the PitchWeb, that allow listeners to participate actively and creatively; and the possibility that a new form of music is emerging are discussed. This new music, Virtual Music, is a new art form, within a new medium, producing a new type of interactive artistic experience, with the ability to draw in and engage its listeners in the creative process.
Propositional Music from Extended Musical Interface with the Human Nervous System
Authors: ROSENBOOM DAVID
Published: January 2004

Abstract: Results obtained from projects in which self‐organizing musical structures spontaneously arise through electrical interface between the brain and generative musical systems are surveyed. This provides a springboard for examining important paradigm shifts taking place in our thinking about what musical forms can be and how this might influence efforts to increase our understanding of the underlying neural dynamics. Implications of this work for the design of music curricula are considered, emphasizing the importance of active imaginative listening. A view of composing, termed “propositional music,” is introduced in which the proposition of cognitive models of music is an ongoing part of creative musical activity.
Translation from Neurobiological Data to Music Parameters
Authors: MINCIACCHI DIEGO
Published: January 2004

Abstract:Composers have explored different ways to use biological information for the realization of music. Throughout the decades, biological findings have been repeatedly indicated as a source of inspiration or a reservoir of extramusical material for musical composition. More radical and fertile are attempts to produce music systematically using biological data in processes called data sonification or biofeedback techniques. Presented here is a novel strategy of translation where populations of neurobiological data are converted into relational structures from which sound objects are generated by flexible and homogeneous control of the sound parameters. All brain data originate from experiments performed with standard anatomical and physiological techniques, and results of studies based on these experimental materials have already been published. During the translation processes, the information for every sound parameter (such as pitch, duration, envelope, and dynamics) is never derived from fixed transcriptions of data properties. Rather, the space and/or the time interrelations of data populations are used to obtain indexes for sound construction. In this way, equivalent sets of information are exploited to model, or sculpt, the different parameters of sound objects. Three examples from the last decade's personal productions are given. The first refers to the microformal aspects of sound aggregation and is based on data from a microstimulation experiment in the motor cortex. The second describes the earliest translation process developed for live performance with conventional instruments and is based on experiments using a conventional tract tracing technique to compare selected spinal‐projecting cell populations in two differently organized brains. The third outlines a recent music production for three pianos based on data from experiments using the multiple fluorescent tract‐tracing technique to simultaneously label different populations of thalamocortical neurons. The approach here described can potentially contribute to a unitary view of the different sound parameters and of the micro‐ and macroformal aspects of the compositional process.
Brain and Sound Resonance
Authors: RADULESCU HORATIU
Published: January 2004

Abstract: The author discusses the “preferential phenomenology” of sound spectra. Most interesting have been the sound relations that result from special filtering according to “rings” of resonance. Mathematical operations are required to describe this filtering of frequency multiples—spectral components—producing sum and difference tones. With new harmonic formats, a new phenomenological vocabulary of music is achieved that evolves far beyond its historical language.
Effects of Relaxing Music on Salivary Cortisol Level after Psychological Stress
Authors: KHALFA STÉPHANIE , BELLA SIMONE DALLA , ROY MATHIEU , PERETZ ISABELLE , LUPIEN SONIA J.
Published: January 2004

Abstract:The goal of the present study was to determine whether relaxing music (as compared to silence) might facilitate recovery from a psychologically stressful task. To this aim, changes in salivary cortisol levels were regularly monitored in 24 students before and after the Trier Social Stress Test. The data show that in the presence of music, the salivary cortisol level ceased to increase after the stressor, whereas in silence it continued to increase for 30 minutes.
Introductory Remarks on Musical Beginnings: Ten Years Later
Authors: FAIENZA CARMINE , COSSU GIUSEPPE
Published: January 2004

Abstract: Over the last 10 years, the neurosciences have witnessed an exponential increase of research in the neuropsychology of music. Consequently, old and new questions on the ontogeny of musical skills can be refined and reformulated with greater accuracy. Three interrelated issues are discussed.
Musical Learning and Language Development
Authors: SAFFRAN JENNY R.
Published: January 2004

Abstract:How do infant learners acquire structure, given complex environ‐ments? In this chapter, we consider the role played by statistical learning—tracking patterns in the environment—in the acquisition of language and music. The results from a series of experiments suggest that similar learning mechanisms may operate in both domains, but that these mechanisms are also influenced by domain‐specific perceptual biases and input structure.
Toward a Developmental Psychology of Music
Authors: TREHUB SANDRA E.
Published: January 2004

Abstract:Research on music perception has revealed numerous parallels between infants and adults, but these findings have had little influence on adult research. Studies of pitch memory in infants, children, and adults are presented to illustrate potential gains from a developmental approach. Although the prevailing wisdom is that absolute pitch processing dominates in early life until it is supplanted by relative pitch processing, recent research offers no support for that view. After a week of exposure to English folk melodies, infants remember the melodies, but they do not distinguish the original versions from transposed versions. Relative pitch processing dominates later on, but it does not occur at the expense of absolute pitch processing. For example, adults can identify the pitch level of familiar musical recordings in the context of foils that are pitch shifted by one or two semitones. Children 5‐9 years of age can identify the pitch level of familiar recordings when the foils are pitch shifted by two semitones but not by one semitone. By contrast, Japanese children are successful in the context of one‐semitone shifts. In short, a developmental approach can provide insights of comparable importance on many issues in music cognition.