bluuebunny/crossref_metadata_2025 huggingface dataset:
Uses and interpretations of non‐word repetition tasks in children with and without specific language impairments (SLI)
Authors: Coady Jeffry A. , Evans Julia L.
Published: January 2008

Background: The non‐word repetition task (NRT) has gained wide acceptance in describing language acquisition in both children with normal language development (NL) and children with specific language impairments (SLI). This task has gained wide acceptance because it so closely matches the phonological component of word learning, and correlates with measures of phonological working memory, a deficit in which is hypothesized to underlie SLI.

Aims/Methods & Procedures: Recent uses of the NRT seem to accept it as a measure of phonological working memory capacity in spite of the fact that researchers have consistently acknowledged that the task taps many language processes, including speech perception, phonological encoding, phonological memory, phonological assembly and articulation. This paper reviews the literature on the use of the non‐word repetition task (NRT) in children with NL and children with SLI, emphasizing the component skills necessary for successful repetition.

Main Contribution: For children with NL, discussion has focused on (1) the relationship between non‐word repetition ability and vocabulary, and (2) lexical and sublexical influences on repetition accuracy. For children with SLI, discussion has focused on these factors as well, but has also considered other component skills that support non‐word repetition. Researchers have examined speech perception and discrimination, phonological encoding, phonological memory, phonological assembly, motor planning, and articulation, and have found evidence that children with SLI exhibit impairments in each of these supporting skills.

Conclusions: Because repetition accuracy depends on lexical and sublexical properties, the NRT can be used to examine the structural properties of the lexicon in both children with NL and with SLI. Further, because the task taps so many underlying skills, it is a powerful tool that can be used to identify children with language impairments.
Reliability of speech diadochokinetic test measurement
Authors: Gadesmann Miriam , Miller Nick
Published: January 2008

Background: Measures of articulatory diadochokinesis (DDK) are widely used in the assessment of motor speech disorders and they play a role in detecting abnormality, monitoring speech performance changes and classifying syndromes. Although in clinical practice DDK is generally measured perceptually, without support from instrumental methods that display the acoustic waveform, no standard measurement procedures are employed and studies on inter‐ and intra‐rater reliability are lacking.

Aims: To investigate the inter‐ and intra‐rater reliability of perceptual DDK measurement and the possible impact of experience on rating performance.

Methods & Procedures: Ten speech and language therapists and ten untrained controls rated 12 DDK speech samples, including two pairs of identical samples, of speakers with different neurological speech disorders. We compared timing for repetitions as close as possible to 5 s, for 5 s exactly, and for as long as the speaker could manage; as well as four qualitative features (rhythm, distinctness, loudness and overall impression). Counts by time were compared with objective outcomes from sound spectrograms.

Outcomes & Results: Inter‐ and intra‐rater reliability was lower than should be acceptable for clinical diagnostic and outcome assessment. The most accurate and repeatable procedure (compared with objective measurement) was counting the syllables within the first 5 s. There was no unequivocal influence of clinical experience on accuracy.

Conclusions: The findings suggest caution in employing and interpreting clinical DDK measures as diagnostic and outcome measures. More research is necessary to settle the influence of experience on time and count accuracy and what modifications to timing might bring increased agreement that permits DDK to realize its full potential in assessment.
Inhibitory Sensory Preconditioning Detected with a Sodium Depletion Procedure
Authors: Espinet Alfredo , Artigas Antonio A. , Balleine Ernard W.
Published: January 2008

In each of two experiments, two groups of rats were exposed to three flavoured solutions: A (citric acid), B (salt), and AX (a compound of citric acid and saccharin). Both experiments used a between-subjects design in which a paired group received presentations of A followed by B, alternating with presentations of AX (i.e., A → B/AX), and an unpaired group received alternating presentations of A, B, and AX (i.e., A/B/AX). This arrangement was expected to establish X as an inhibitor of B in group paired but not in group unpaired. In Experiment 1, after preexposure all subjects received a single presentation of an XB compound, then experienced sodium depletion, and were tested for their consumption of X, which was greater in group unpaired than in group paired. In Experiment 2, after preexposure, all subjects received four presentations of a new flavour, C, in compound with B and subsequently, under sodium depletion, were tested for consumption of XC. Intake of the XC compound was less in group paired than in group unpaired. These results suggest that, in group paired, X acquired an inhibitory relationship with B both retarding the acquisition of an excitatory association with B (retardation test, Experiment 1) and reducing the response to a new stimulus, C, strongly associated to B (summation test, Experiment 2). These results provide direct evidence of inhibition between two neutral stimuli and, therefore, of inhibitory sensory preconditioning.
Slowing down an Internal Clock: Implications for Accounts of Performance on four Timing Tasks
Authors: Wearden J. H.
Published: January 2008

An experiment investigated the potential effects of lowering arousal on performance on time perception tasks. Four participant groups received different tasks: Normal and episodic temporal generalization, bisection, and verbal estimation, all involving judgements of the duration of visual stimuli. Self-rated arousal during the experimental session was lowered by spacing experimental trials approximately 10 s apart. Between the early and late blocks of the experiment, performance changed on normal temporal generalization and verbal estimation, but not on episodic temporal generalization and bisection. The changes were consistent with the idea that the pacemaker of the participant's internal clock had been slowed down by the slow trial spacing. Results suggested that bisection was based on a criterion that adjusted during the experiment, whereas verbal estimation was based on preexisting standards, or those established early in the experiment.
Phonological Similarity and Lexicality Effects in Children's Verbal Short-Term Memory: Concerns about the Interpretation of Probed Recall Data
Authors: Jarrold Christopher , Cocksey Joanne , Dockerill Emma
Published: January 2008

Probed recall tasks are often used to assess aspects of children's verbal short-term memory development because they are not subject to potentially confounding output effects. However, the marked recency effects that are observed in probed recall means that these tasks are potentially insensitive to experimental manipulations when later serial positions are probed. This clouds the interpretation of data from probed recall studies in which children of different ages are presented with to-be-remembered lists of different lengths. In two experiments we examined the magnitude of phonological similarity and lexicality effects in both 5- to 6- and 8- to 9-year-old children. In each case performance on probed recall tasks was contrasted with that seen on tests of serial recognition. The results indicated that probed recall tasks are potentially less sensitive to experimental manipulations in younger than older children. However, comparable effects of both phonological similarity and lexicality were seen in both age groups using serial recognition procedures. These findings have implications for the interpretation of other studies that have examined the development of verbal short-term memory using probed recall and for theoretical accounts of the development of phonological similarity and lexicality effects in children.
List Strength Effect without List Length Effect in Recognition Memory
Authors: Buratto Luciano G. , Lamberts Koen
Published: January 2008

The study of list length effects (adding items to a list affects memory for the other items) and list strength effects (strengthening some items in a list affects memory for the nonstrengthened items) is important to constrain models of memory. In recognition memory, a list length effect is generally found, whereas a list strength effect is not. Using the switched-plurality procedure in an old–new recognition task (e.g., study banana; test bananas), we found the opposite pattern. Length manipulations caused no change in memory performance, whereas strength manipulations did. The list strength effect was found when recollection was likely to operate at test (with switched-plurality lures). When recollection was unlikely to operate (with unrelated lures), the strength effect disappeared. The result was observed using both a size judgement task (which has previously produced positive list strength effects) and a pleasantness judgement task (which has not yielded list strength effects before).
Darwinism, Process Structuralism, and Natural Kinds
Authors: Griffiths Paul E.
Published: January 2008

Darwinists classify biological traits either by their ancestry (homology) or by their adaptive role. Only the latter can provide traditional natural kinds, but only the former is practicable. Process structuralists exploit this embarrassment to argue for non-Darwinian classifications in terms of underlying developmental mechanisms. This new taxonomy will also explain phylogenetic inertia and developmental constraint. I argue that Darwinian homologies are natural kinds despite having historical essences and being spatio-temporally restricted. Furthermore, process structuralist explanations of biological form require an unwarranted assumption about the space of developmental possibility.
Innateness and Canalization
Authors: Ariew André
Published: January 2008

Cognitive scientists often employ the notion of innateness without defining it. The issue is, how is innateness defined in biology? Some critics contend that innateness is not a legitimate concept in biology. In this paper I will argue that it is. However, neither the concept of high heritability nor the concept of flat norm of reaction (two popular accounts in the biology literature) define innateness. An adequate account is found in developmental biology. I propose that innateness is best defined in terms of C. H. Waddington's concept of canalization.
Theoretical Modeling and Biological Laws
Authors: Cooper Gregory
Published: January 2008

Recent controversy over the existence of biological laws raises questions about the cognitive aims of theoretical modeling in that science. If there are no laws for successful theoretical models to approximate, then what is it that successful theories do? One response is to regard theoretical models as tools. But this instrumental reading cannot accommodate the explanatory role that theories are supposed to play. Yet accommodating the explanatory function, as articulated by Brandon and Sober for example, seems to involve us once again in a reliance on laws. The paper concludes that we must rethink both the nature of lawsandtheoretical explanation in biology.
Inferences from Phenomena in Gravitational Physics
Authors: Harper William , Disalle Robert
Published: January 2008

Newton's methodology emphasized propositions “inferred from phenomena.” These rest on systematic dependencies that make phenomena measure theoretical parameters. We consider the inferences supporting Newton's inductive argument that gravitation is proportional to inertial mass. We argue that the support provided by these systematic dependencies is much stronger than that provided by bootstrap confirmation; this kind of support thus avoids some of the major objections against bootstrapping. Finally we examine how contemporary testing of equivalence principles exemplifies this Newtonian methodological theme.
Is there a Syntactic Solution to the Hole Problem?
Authors: Rynasiewicz Robert
Published: January 2008

After some background setting in which it is shown how Maudlin's (1989, 1990) response to the hole argument of Earman and Norton (1987) is related to that of Rynasiewicz (1994), it is argued that the syntactic proposals of Mundy (1992) and of Leeds (1995), which claim to dismiss the hole argument as an uninteresting blunder, are inadequate. This leads to a discussion of how the responses of Maudlin and Rynasiewicz relate to issues about gauge freedom and relativity principles.
The Evolution of Color Vision Without Colors
Authors: Hall Richard J.
Published: January 2008

The standard adaptationist explanation of the presence of a sensory mechanism in an organism—that it detects properties useful to the organism—cannot be given for color vision. This is because colors do not exist. After arguing for this latter claim, I consider, but reject, nonadaptationist explanations. I conclude by proposing an explanation of how color vision could have adaptive value even though it does not detect properties in the environment.
True Theories, False Colors
Authors: Clark Austen
Published: January 2008

Recent versions of objectivism can reply to the argument from metamers. The deeper rift between subjectivists and objectivists lies in the question of how to explain the structure of qualitative similarities among the colors. Subjectivism grounded in this fashion can answer the circularity objection raised by Dedrick. It endorses skepticism about the claim that there is some one property of objects that it is the function of color vision to detect. Color vision may enable us to detect differences in spectral composition without granting us the capacity to detect identities.
On What Being a World Takes Away
Authors: Clifton Rob
Published: January 2008

In their article “On What It Takes To Be a World”, David Albert and Jeffrey Barrett raise “a rather urgent question about what the proponents of a many-worlds interpretation [of quantum mechanics] can possibly mean by the term ‘worlds’” (1995, 35). I argue that their considerations do not translate into an argument against the Many-Worlds conception of a world unless one requires that the dispositions that measurement devices display through the outcomes they record be explainable in terms of facts particular to the worlds in which those devices do their recording. Granting that their conception of a world takes away the possibility of such an explanation, a Many-Worlds proponent can claim that the Universal quantum state, which does not represent a fact about any world in particular, is enough to ground the dispositions of measurement devices.
Exposing The Machinery of Infinite Renormalization
Authors: Huggett Nick , Weingard Robert
Published: January 2008

We explicate recent results that shed light on the obscure and troubling problem of renormalization in Quantum Field Theory (QFT). We review how divergent predictions arise in perturbative QFT, and how they are renormalized into finite quantities. Commentators have worried that there is no foundation for renormalization, and hence that QFTs are not logically coherent. We dispute this by describing the physics behind liquid diffusion, in which exactly analogous divergences are found and renormalized. But now we are looking at a problem that is physically and formally well-defined, proving that the problems of renormalization, by themselves, cannot refute QFT.
Testament of A Recovering Eliminativist
Authors: Melnyk Andrew
Published: January 2008

If physicalism is true (e.g., if every event is a fundamental-physical event), then it looks as if there is a fundamental-physical explanation of everything. If so, then what is to become of special scientific explanations? They seem to be excluded by the fundamental-physical ones, and indeed to be excellent candidates for elimination. I argue that, if physicalism is true, there probably is a fundamental-physical explanation of everything, but that nevertheless there can perfectly well be special scientific explanations as well, notwithstanding eliminativist scruples concerning overdetermination and Ockham's Razor.
Stretched Lines, Averted Leaps, And Excluded Competition: A Theory of Scientific Counterfactuals
Authors: Mikkelson Gregory M.
Published: January 2008

Lewis' argument against the Limit Assumption and Pollock's Generalized Consequence Principle together suggest that “minimal-change” theories of counterfactuals are wrong. The “small-change” theories presented by Nute do not say enough. While these theories rely on closeness between possible worlds, I base an alternative on the ceteris paribus concept. My theory solves a problem that the above cannot, and is more relevant to the philosophy of science. Ceteris paribus conditions should normally include the causes, but exclude the effects, of the negated antecedent. An example from community ecology, the debate over null models in island-biogeographical studies of competition, supports these arguments.
Similarity as an Intertheory Relation
Authors: Gorham Geoffrey
Published: January 2008

In line with the semantic conception of scientific theories, I develop an account of the intertheory relation of comparative structural similarity. I argue that this relation is useful in explaining the concept of verisimilitude and I support this contention with a concrete historical example. Finally, I defend this relation against the familiar charge that the concept of similarity is insufficiently objective.
Novelty, Severity, and History in the Testing of Hypotheses: The Case of the Top Quark
Authors: Staley Kent W.
Published: January 2008

It is sometimes held that facts confirm a hypothesis only if they were not used in the construction of that hypothesis. This requirement of “use novelty” introduces a historical aspect into the assessment of evidence claims. I examine a methodological principle invoked by physicists in the experimental search for the top quark that bears a striking resemblance to this view. However, this principle is better understood, both historically and philosophically, in terms of the need to conduct a severe test than in terms of use novelty. Nevertheless, a historical factor remains in the assessment of some evidence claims.
Confirmation and the Indispensability of Mathematics to Science
Authors: Vineberg Susan
Published: January 2008

Quine and Putnam argued for mathematical realism on the basis of the indispensability of mathematics to science. They claimed that the mathematics that is used in physical theories is confirmed along with those theories and that scientific realism entails mathematical realism. I argue here that current theories of confirmation suggest that mathematics does not receive empirical support simply in virtue of being a part of well confirmed scientific theories and that the reasons for adopting a realist view of scientific theories do not support realism about mathematical entities, despite the use of mathematics in formulating scientific theory.
The Curve Fitting Problem: A Bayesian Approach
Authors: Bandyopadhayay Prasanta S. , Boik Robert J. , Vineberg Susan
Published: January 2008

In the curve fitting problem two conflicting desiderata, simplicity and goodness-of-fit, pull in opposite directions. To this problem, we propose a solution that strikes a balance between simplicity and goodness-of-fit. Using Bayes’ theorem we argue that the notion of prior probability represents a measurement of simplicity of a theory, whereas the notion of likelihood represents the theory’s goodness-of-fit. We justify the use of prior probability and show how to calculate the likelihood of a family of curves. We diagnose the relationship between simplicity of a theory and its predictive accuracy.
A Paradox for Empiricism (?)
Authors: Douven Igor
Published: January 2008

According to van Fraassen, constructive empiricism yields a better account of science than does scientific realism. One particularly important advantage van Fraassen claims his position to have over scientific realism is that the former can make sense of science without invoking (what he calls) pre-Kantian metaphysics. In the present paper the consistency of van Fraassen’s position is put in doubt. Specifically, it will be argued that van Fraassen faces the paradox that he cannot do with nor without the pre-Kantian metaphysics he abhors.
Logical Foundations for Modal Interpretations of Quantum Mechanics
Authors: Dickson Michael
Published: January 2008

This paper proposes a logic, motivated by modal interpretations, in which every quantum mechanics propositions has a truth-value. This logic is completely classical, hence violates the conditions of the Kochen-Specker theorem. It is shown how the violation occurs, and it is argued that this violation is a natural and acceptable consequence of modal interpretations. It is shown that despite its classicality, the proposed logic is empirically indistinguishable from quantum logic.
Van Fraassen on Preparation and Measurement
Authors: Ruetsche Laura
Published: January 2008

Van Fraassen’s 1991 modal interpretation of Quantum Mechanics offers accounts of measurement and state preparation. I argue that both accounts overlook a class of interactions I call General Unitary Measurements, or GUMs. Ironically, GUMs are significant for van Fraassen’s account of measurement because they challenge it, and significant for his account of preparation because they simplify it. Van Fraassen’s oversight prompts a question about modal interpretations: developed to account for ideal measurement outcomes, can they consistently account as well for the whole horizon of laboratory practices by which we investigate QM?
Density limit study focusing on the edge plasma parameters in LHD
Authors: Miyazawa J. , Sakamoto R. , Masuzaki S. , Peterson B.J. , Tamura N. , Goto M. , Yamada I. , Narihara K. , Tanaka K. , Tokuzawa T. , Shoji M. , Kobayashi M. , Arimoto H. , Kondo K. , Murakami S. , Funaba H. , Sakakibara S. , Osakabe M. , Morita S. , Nagayama Y. , Ohyabu N. , Yamada H. , Komori A. , Motojima O.
Published: January 2008

In the Large Helical Device (LHD) experiment, complete detachment takes place when the plasma column shrinks inside the last-closed-flux-surface (LCFS). The density at the LCFS that results in this shrinking corresponds to the maximum LCFS density achievable under the attached condition. The critical LCFS density increases with the square root of the heating power, as is predicted by the conventional density limit scaling for helical plasmas, called the Sudo scaling. High line-averaged electron densities reaching 3 × 1020 m−3, which correspond to ∼3 times as high as the Sudo scaling, have been achieved in the plasmas with strongly peaked density profiles generated by hydrogen ice pellet injection. Even in the pellet-fuelled plasmas, however, the LCFS densities are similar to those in gas-fuelled plasmas with flat density profiles and well reproduced by Sudo scaling with a factor 0.8. According to these observations, Sudo scaling has been reinterpreted as the ‘edge’ density limit scaling. The square root type power dependence in the Sudo scaling has been reconsidered. Instead of a simple power balance between the heating power and the radiation loss, it is deduced by combining the critical LCFS temperature for complete detachment and the electron temperature dependence on the heating power and the electron density. Higher edge density than in the attached plasmas can be sustained in the completely detached plasmas, where the plasma edge shrinks inside the LCFS. The edge density limit scaling is extended for completely detached plasmas by taking into account the shrinking plasma edge.
Automated programming for bioinformatics algorithm deployment
Authors: Alterovitz Gil , Jiwaji Adnaan , Ramoni Marco F.
Published: January 2008

Summary: Many bioinformatics solutions suffer from the lack of usable interface/platform from which results can be analyzed and visualized. Overcoming this hurdle would allow for more widespread dissemination of bioinformatics algorithms within the biological and medical communities. The algorithms should be accessible without extensive technical support or programming knowledge. Here, we propose a dynamic wizard platform that provides users with a Graphical User Interface (GUI) for most Java bioinformatics library toolkits. The application interface is generated in real-time based on the original source code. This platform lets developers focus on designing algorithms and biologists/physicians on testing hypotheses and analyzing results.

Availability: The open source code can be downloaded from: http://bcl.med.harvard.edu/proteomics/proj/APBA/

Contact:  gil@mit.edu
Prediction of protein functional residues from sequence by probability density estimation
Authors: Fischer J. D. , Mayer C. E. , Söding J.
Published: January 2008

Motivation: The prediction of ligand-binding residues or catalytically active residues of a protein may give important hints that can guide further genetic or biochemical studies. Existing sequence-based prediction methods mostly rank residue positions by evolutionary conservation calculated from a multiple sequence alignment of homologs. A problem hampering more wide-spread application of these methods is the low per-residue precision, which at 20% sensitivity is around 35% for ligand-binding residues and 20% for catalytic residues.

Results: We combine information from the conservation at each site, its amino acid distribution, as well as its predicted secondary structure (ss) and relative solvent accessibility (rsa). First, we measure conservation by how much the amino acid distribution at each site differs from the distribution expected for the predicted ss and rsa states. Second, we include the conservation of neighboring residues in a weighted linear score by analytically optimizing the signal-to-noise ratio of the total score. Third, we use conditional probability density estimation to calculate the probability of each site to be functional given its conservation, the observed amino acid distribution, and the predicted ss and rsa states.

We have constructed two large data sets, one based on the Catalytic Site Atlas and the other on PDB SITE records, to benchmark methods for predicting functional residues. The new method FRcons predicts ligand-binding and catalytic residues with higher precision than alternative methods over the entire sensitivity range, reaching 50% and 40% precision at 20% sensitivity, respectively.

Availability: Server: http://frpred.tuebingen.mpg.de. Data sets: ftp://ftp.tuebingen.mpg.de/pub/protevo/FRpred/

Contact:  soeding@lmb.uni-muenchen.de

Supplementary information: Supplementary data are available at Bioinformatics Online.
Beyond the ‘best’ match: machine learning annotation of protein sequences by integration of different sources of information
Authors: Tetko Igor V. , Rodchenkov Igor V. , Walter Mathias C. , Rattei Thomas , Mewes Hans-Werner
Published: January 2008

Motivation: Accurate automatic assignment of protein functions remains a challenge for genome annotation. We have developed and compared the automatic annotation of four bacterial genomes employing a 5-fold cross-validation procedure and several machine learning methods.

Results: The analyzed genomes were manually annotated with FunCat categories in MIPS providing a gold standard. Features describing a pair of sequences rather than each sequence alone were used. The descriptors were derived from sequence alignment scores, InterPro domains, synteny information, sequence length and calculated protein properties. Following training we scored all pairs from the validation sets, selected a pair with the highest predicted score and annotated the target protein with functional categories of the prototype protein. The data integration using machine-learning methods provided significantly higher annotation accuracy compared to the use of individual descriptors alone. The neural network approach showed the best performance. The descriptors derived from the InterPro domains and sequence similarity provided the highest contribution to the method performance. The predicted annotation scores allow differentiation of reliable versus non-reliable annotations. The developed approach was applied to annotate the protein sequences from 180 complete bacterial genomes.

Availability: The FUNcat Annotation Tool (FUNAT) is available on-line as Web Services at http://mips.gsf.de/proj/funat

Contact:  i.tetko@gsf.de

Supplementary information: Supplementary data are available at Bioinformatics online.
Likelihood-based estimation of continuous-time epidemic models from time-series data: application to measles transmission in London
Authors: Cauchemez Simon , Ferguson Neil M
Published: January 2008

We present a new statistical approach to analyse epidemic time-series data. A major difficulty for inference is that (i) the latent transmission process is partially observed and (ii) observed quantities are further aggregated temporally. We develop a data augmentation strategy to tackle these problems and introduce a diffusion process that mimicks the susceptible–infectious–removed (SIR) epidemic process, but that is more tractable analytically. While methods based on discrete-time models require epidemic and data collection processes to have similar time scales, our approach, based on a continuous-time model, is free of such constraint. Using simulated data, we found that all parameters of the SIR model, including the generation time, were estimated accurately if the observation interval was less than 2.5 times the generation time of the disease. Previous discrete-time TSIR models have been unable to estimate generation times, given that they assume the generation time is equal to the observation interval. However, we were unable to estimate the generation time of measles accurately from historical data. This indicates that simple models assuming homogenous mixing (even with age structure) of the type which are standard in mathematical epidemiology miss key features of epidemics in large populations.
Species differences in Cl− affinity and in electrogenicity of SLC26A6‐mediated oxalate/Cl− exchange correlate with the distinct human and mouse susceptibilities to nephrolithiasis
Authors: Clark Jeffrey S. , Vandorpe David H. , Chernova Marina N. , Heneghan John F. , Stewart Andrew K. , Alper Seth L.
Published: January 2008

The mouse is refractory to lithogenic agents active in rats and humans, and so has been traditionally considered a poor experimental model for nephrolithiasis. However, recent studies have identified slc26a6 as an oxalate nephrolithiasis gene in the mouse. Here we extend our earlier demonstration of different anion selectivities of the orthologous mouse and human SLC26A6 polypeptides to investigate the correlation between species‐specific differences in SLC26A6 oxalate/anion exchange properties as expressed in Xenopus oocytes and in reported nephrolithiasis susceptibility. We find that human SLC26A6 mediates minimal rates of Cl− exchange for Cl−, sulphate or formate, but rates of oxalate/Cl− exchange roughly equivalent to those of mouse slc2a6. Both transporters exhibit highly cooperative dependence of oxalate efflux rate on extracellular [Cl−], but whereas the K1/2 for extracellular [Cl−] is only 8 mm for mouse slc26a6, that for human SLC26A6 is 62 mm. This latter value approximates the reported mean luminal [Cl−] of postprandial human jejunal chyme, and reflects contributions from both transmembrane and C‐terminal cytoplasmic domains of human SLC26A6. Human SLC26A6 variant V185M exhibits altered [Cl−] dependence and reduced rates of oxalate/Cl− exchange. Whereas mouse slc26a6 mediates bidirectional electrogenic oxalate/Cl− exchange, human SLC26A6‐mediated oxalate transport appears to be electroneutral. We hypothesize that the low extracellular Cl− affinity and apparent electroneutrality of oxalate efflux characterizing human SLC26A6 may partially explain the high human susceptibility to nephrolithiasis relative to that of mouse. SLC26A6 sequence variant(s) are candidate risk modifiers for nephrolithiasis.
Biophysical properties of CaV1.3 calcium channels in gerbil inner hair cells
Authors: Johnson Stuart L. , Marcotti Walter
Published: January 2008

The Ca2+ current (ICa) in prehearing and adult inner hair cells (IHCs), the primary sensory receptors of the mammalian cochlea, is mainly carried by L‐type (CaV1.3) Ca2+ channels. ICa in immature and adult IHCs triggers the release of neurotransmitter onto auditory afferent fibres in response to spontaneous action potentials (APs) or graded receptor potentials, respectively. We have investigated whether the biophysical properties of ICa vary between low‐ and high‐frequency IHCs during cochlear development and whether its inactivation influences cellular responses. ICa was recorded from gerbil IHCs maintained near physiological recording conditions. The size of ICa in adult IHCs was about a third of that in immature cells with no apparent difference along the cochlea at both stages. The activation kinetics of ICa were significantly faster in high‐frequency IHCs, with that of adult cells being more rapid than immature cells. The degree of ICa inactivation was similar along the immature cochlea but larger in high‐ than low‐frequency adult IHCs. This inactivation was greatly reduced with barium but not affected by changing the intracellular buffer (BAPTA instead of EGTA). Immature basal IHCs showed faster recovery of ICa from inactivation than apical cells allowing them to support a higher AP frequency. ICa in adult IHCs was more resistant to progressive inactivation following repeated voltage stimulation than that of immature cells. This suggests that adult IHCs are likely to be suited for sustaining rapid and repeated release of synaptic vesicles, which is essential for sound encoding.
A comparison of filter design structures for multi-channel acoustic communication systems
Authors: Dumuid Pierre M. , Cazzolato Ben S. , Zander Anthony C.
Published: January 2008

The application of inverse filter designs as a means of providing improved communication performance in acoustic environments is investigated. Tikhonov regularized inverse filters of channel transfer functions calculated in the frequency domain are used as a means of obtaining multi-channel filters. Three classifications of inverse filter structures have been considered using time-domain simulations. The performance of Tikhonov regularized inverse filters designed according to each of these classifications is compared with each other and against a filter design developed by Stojanovic [Stojanovic, M. (2005). “Retrofocusing techniques for high rate acoustic communications,” J. Acoust. Soc. Am. 117, 1173–1185]. It is shown that the filter design developed by Stojanovic requires less regularization and outperforms the Tikhonov regularized inverse filter designs when communicating over a single channel. While the filter developed by Stojanovic is designed to use multiple transmitters to transmit to a single receiver, the filter was implemented in a multi-channel system and proposed to have a focusing similar to that obtained using time-reversal. It was found that for the scenario used in the simulation, the Tikhonov regularized inverse design for full multi-channel inversion achieved better focusing than the design by Stojanovic, where simulation results show 20dB less cross-talk at the expense of around 2dB loss in signal strength.
The foreign language cocktail party problem: Energetic and informational masking effects in non-native speech perception
Authors: Cooke Martin , Garcia Lecumberri M. L. , Barker Jon
Published: January 2008

Studies comparing native and non-native listener performance on speech perception tasks can distinguish the roles of general auditory and language-independent processes from those involving prior knowledge of a given language. Previous experiments have demonstrated a performance disparity between native and non-native listeners on tasks involving sentence processing in noise. However, the effects of energetic and informational masking have not been explicitly distinguished. Here, English and Spanish listener groups identified keywords in English sentences in quiet and masked by either stationary noise or a competing utterance, conditions known to produce predominantly energetic and informational masking, respectively. In the stationary noise conditions, non-native talkers suffered more from increasing levels of noise for two of the three keywords scored. In the competing talker condition, the performance differential also increased with masker level. A computer model of energetic masking in the competing talker condition ruled out the possibility that the native advantage could be explained wholly by energetic masking. Both groups drew equal benefit from differences in mean F0 between target and masker, suggesting that processes which make use of this cue do not engage language-specific knowledge.
Harmonic pulsed excitation and motion detection of a vibrating reflective target
Authors: Urban Matthew W. , Greenleaf James F.
Published: January 2008

Elasticity imaging is an emerging medical imaging modality. Methods involving acoustic radiation force excitation and pulse-echo ultrasound motion detection have been investigated to assess the mechanical response of tissue. In this work new methods for dynamic radiation force excitation and motion detection are presented. The theory and model for harmonic motion detection of a vibrating reflective target are presented. The model incorporates processing of radio frequency data acquired using pulse-echo ultrasound to measure harmonic motion with amplitudes ranging from 100to10,000nm. A numerical study was performed to assess the effects of different parameters on the accuracy and precision of displacement amplitude and phase estimation and showed how estimation errors could be minimized. Harmonic pulsed excitation is introduced as a multifrequency radiation force excitation method that utilizes ultrasound tonebursts repeated at a rate fr. The radiation force, consisting of frequency components at multiples of fr, is generated using 3.0MHz ultrasound, and motion detection is performed simultaneously with 9.0MHz pulse-echo ultrasound. A parameterized experimental analysis showed that displacement can be measured with small errors for motion with amplitudes as low as 100nm. The parameterized numerical and experimental analyses provide insight into how to optimize acquisition parameters to minimize measurement errors.
Effect of age, presentation method, and learning on identification of noise-vocoded words
Authors: Sheldon Signy , Pichora-Fuller M. Kathleen , Schneider Bruce A.
Published: January 2008

Noise vocoding was used to investigate the ability of younger and older adults with normal audiometric thresholds in the speech range to use amplitude envelope cues to identify words. In Experiment 1, four 50-word lists were tested, with each word presented initially with one frequency band and the number of bands being incremented until it was correctly identified by the listener. Both age groups required an average of 5.25 bands for 50% correct word identification and performance improved across the four lists. In Experiment 2, the same participants who completed Experiment 1 identified words in four blocked noise-vocoded conditions (16, 8, 4, 2 bands). Compared to Experiment 1, both age groups required more bands to reach the 50% correct word identification threshold in Experiment 2, 6.13, and 8.55 bands, respectively, with younger adults outperforming older adults. Experiment 3 was identical to Experiment 2 except the participants had no prior experience with noise-vocoded speech. Again, younger adults outperformed older adults, with thresholds of 6.67 and 8.97 bands, respectively. The finding of age effects in Experiments 2 and 3, but not in Experiment 1, seems more likely to be related to differences in the presentation methods than to experience with noise vocoding.
Spatial correlation and coherence in reverberant acoustic fields: Extension to microphones with arbitrary first-order directivity
Authors: Kuster Martin
Published: January 2008

Spatial correlation and coherence functions in reverberant sound fields are relevant to the acoustics of enclosed spaces and related areas. Theoretical expressions for the spatial correlation and coherence functions between signals representing the pressure and/or the components of the particle velocity vector in a reverberant sound field are established in the literature and most of these have also been corroborated with measurements [F. Jacobsen, J. Acoust. Soc. Am. 108, 204–210 (2000)]. In the present paper, these expressions are generalized to microphones of first-order directivity, whereby the directivity can be expressed in terms of pressure and pressure gradient. It is shown that the resulting spatial correlation and coherence functions can be expressed in terms of the established spatial correlation and coherence functions. The derived theoretical expression for the spatial coherence function is validated with a modeled diffuse sound field. Further, it is compared with the experimental coherence obtained from the reverberant tails of room impulse responses measured with two common surround sound microphone setups in a concert and a lecture hall.
Listeners’ sensitivity to “onset/offset” and “ongoing” interaural delays in high-frequency, sinusoidally amplitude-modulated tones
Authors: Buell Thomas N. , Griffin Sarah J. , Bernstein Leslie R.
Published: January 2008

The relative potency of onset/offset and envelope-based ongoing interaural time delays (ITDs) was assessed using high-frequency stimuli. A two-cue, two-alternative, forced-choice adaptive task was employed to measure threshold ITDs with 100% sinusoidally amplitude-modulated tones centered at 4kHz. Modulation rates of 125, 250, and 350Hz were tested with durations of 32, 90, or 240ms. In the first experiment, ITDs to be detected were imposed only at the onset/offset, only within the ongoing portion, or within both the onset/offset and ongoing portions of the stimuli. Results indicated that ongoing ITDs dominated onset/offset ITDs. The relative potency of ongoing ITDs was directly proportional to duration and inversely proportional to modulation rate. Quantitative analysis suggested that listeners effectively combine onset/offset and ongoing ITDs. Furthermore, the data could be largely accounted for by assuming that listeners attend to the interaural decorrelation of the stimulus resulting from onset/offset and/or ongoing ITDs. A second experiment showed that, (1) overall, an ongoing ITD of one-half period of the envelope had little impact on listeners’ sensitivity to delays of the onset/offset and (2) sensitivity to delays within the onset/offset portion of the waveform was reduced by roving the delay within the ongoing portion of the waveform.
Sample discrimination of frequency by hearing-impaired and normal-hearing listeners
Authors: Alexander Joshua M. , Lutfi Robert A.
Published: January 2008

In a multiple observation, sample discrimination experiment normal-hearing (NH) and hearing-impaired (HI) listeners heard two multitone complexes each consisting of six simultaneous tones with nominal frequencies spaced evenly on an ERBN logarithmic scale between 257 and 6930Hz. On every trial, the frequency of each tone was sampled from a normal distribution centered near its nominal frequency. In one interval of a 2IFC task, all tones were sampled from distributions lower in mean frequency and in the other interval from distributions higher in mean frequency. Listeners had to identify the latter interval. Decision weights were obtained from multiple regression analysis of the between- interval frequency differences for each tone and listeners’ responses. Frequency difference limens (an index of sensorineural resolution) and decision weights for each tone were used to predict the sensitivity of different decision-theoretic models. Results indicate that low-frequency tones were given much greater perceptual weight than high-frequency tones by both groups of listeners. This tendency increased as hearing loss increased and as sensorineural resolution decreased, resulting in significantly less efficient weighting strategies for the HI listeners. Overall, results indicate that HI listeners integrated frequency information less optimally than NH listeners, even after accounting for differences in sensorineural resolution.
Across-channel interference in intensity discrimination: The role of practice and listening strategy
Authors: Buss Emily
Published: January 2008

Pure tone intensity discrimination thresholds can be elevated by the introduction of remote maskers with roved level. This effect is on the order of 10dB [10log(ΔI∕I)] in some conditions and can be demonstrated under conditions of little or no energetic masking. The current study examined the effect of practice and observer strategy on this phenomenon. Experiment 1 included observers who had no formal experience with intensity discrimination and provided training over 6h on a single masked intensity discrimination task to assess learning effects. Thresholds fell with practice for most observers, with significant improvements in six out of eight cases. Despite these improvements significant masking remained in all cases. The second experiment assessed trial-by-trial effects of roved masker level. Conditional probability of a “signal-present” response as a function of the rove value assigned to each of the two masker tones indicates fundamental differences among observers’ processing strategies, even after 6h of practice. The variability in error patterns across practiced listeners suggests that observers approach the task differently, though this variability does not appear to be related to sensitivity.
Auditory-visual speech perception in normal-hearing and cochlear-implant listeners
Authors: Desai Sheetal , Stickney Ginger , Zeng Fan-Gang
Published: January 2008

The present study evaluated auditory-visual speech perception in cochlear-implant users as well as normal-hearing and simulated-implant controls to delineate relative contributions of sensory experience and cues. Auditory-only, visual-only, or auditory-visual speech perception was examined in the context of categorical perception, in which an animated face mouthing ∕ba∕, ∕da∕, or ∕ga∕ was paired with synthesized phonemes from an 11-token auditory continuum. A three-alternative, forced-choice method was used to yield percent identification scores. Normal-hearing listeners showed sharp phoneme boundaries and strong reliance on the auditory cue, whereas actual and simulated implant listeners showed much weaker categorical perception but stronger dependence on the visual cue. The implant users were able to integrate both congruent and incongruent acoustic and optical cues to derive relatively weak but significant auditory-visual integration. This auditory-visual integration was correlated with the duration of the implant experience but not the duration of deafness. Compared with the actual implant performance, acoustic simulations of the cochlear implant could predict the auditory-only performance but not the auditory-visual integration. These results suggest that both altered sensory experience and improvised acoustic cues contribute to the auditory-visual speech perception in cochlear-implant users.