Asymmetric Sampling Research Articles

Geometric effect on the phase transition in mesoscopic loops threaded by an Aharonov-Bohm flux

The quantum phase transition in mesoscopic noncircular loops threaded by an Aharonov-Bohm flux is systematically investigated by numerically solving the Bogoliubov-de Gennes equations self-consistently. We focus on the magnetic flux dependence of the s-wave superconducting order parameter and current in symmetric and asymmetric samples. The influence of surface indentation or bulge defects positioned at the inner or outer edge of the sample on the periodic oscillation is also discussed. We find various hc/e-flux periodicity evolution patterns, and the periodic phase transitions between the superconducing state and the resistive/normal state are demonstrated besides the superconducing state transitions. Our investigation may shed new light on material engineering and provide important insights to designing superconducting quantum devices.

Environmental Impact Assessment: Detecting Changes in Fish Community Structure in Response to Disturbance with an Asymmetric Multivariate BACI Sampling Design

One of the primary challenges to detecting anthropogenic environmental impacts is the high degree of spatial and temporal variability inherent in natural systems. Planned or routine events that result in disturbance to populations and communities provide an opportunity for scientists to apply well-replicated and statistically powerful sampling designs to assess subsequent biological effects. For example, a thick layer of sessile invertebrates is the prominent biotic feature of intertidal and shallow subtidal portions of offshore petroleum platforms in southern California. Given the central role of such invertebrates in providing food and shelter, their presence can reasonably be expected to influence associated fish community structure. At one platform on the San Pedro Shelf, invertebrate biomass was completely removed from support pilings and horizontal crossmembers to a depth of 20 m with high-pressure water during a standard “hydrocleaning” event in November 2007. Three nearby platforms remained undisturbed, providing a unique opportunity to test for disturbance-related changes in the local fish assemblage and the overall time course of community recovery. The potential impact of the abrupt and intense removal of the invertebrate layer was assessed with survey data collected periodically for one year prior- and one year post-hydrocleaning in a modified Before-After-Control-Impact (BACI) design. Asymmetrical multivariate analyses of variance revealed a significant effect of disturbance to fish, driven largely by reductions in the abundance of numerically dominant blacksmith (Chromis punctipinnis). Nevertheless, the system was surprisingly resilient, recovering to pre-disturbance conditions within ten months. Our results demonstrate that a well-replicated BACI sampling design can detect even subtle biological changes in response to disturbance, a key step towards developing a mechanistic understanding of community disassembly in the face of increasingly frequent and intense perturbations.

Right and left perisylvian cortex and left inferior frontal cortex mediate sentence‐level rhyme detection in spoken language as revealed by sparse fMRI

In this study, we used functional magnetic resonance imaging to investigate the neural basis of auditory rhyme processing at the sentence level in healthy adults. In an explicit rhyme detection task, participants were required to decide whether the ending syllable of a metrically spoken pseudosentence rhymed or not. Participants performing this task revealed bilateral activation in posterior-superior temporal gyri with a much more extended cluster of activation in the right hemisphere. These findings suggest that the right hemisphere primarily supports suprasegmental tasks, such as the segmentation of speech into syllables; thus, our findings are in line with the "asymmetric sampling in time" model suggested by Poeppel (: Speech Commun 41:245-255). The direct contrast between rhymed and nonrhymed trials revealed a stronger BOLD response for rhymed trials in the frontal operculum and the anterior insula of the left hemisphere. Our results suggest an involvement of these frontal regions not only in articulatory rehearsal processes, but especially in the detection of a matching syllable, as well as in the execution of rhyme judgment.

Dynamic characterization of partially saturated engineered porous media and gas diffusion layers using hydraulic admittance

Simple laboratory methods for determining liquid water distribution in polymer electrolyte membrane fuel cell gas diffusion layers (GDLs) are needed to engineer better GDL materials. Capillary pressure vs. liquid saturation measurements are attractive, but lack the ability to probe the hydraulic interconnectivity and distribution within the pore structure. Hydraulic admittance measurements of simple capillary bundles have recently been shown to nicely measure characteristics of the free-interfaces and hydraulic path. Here we examine the use of hydraulic admittance with a succession of increasingly complex porous media, starting with a laser-drilled sample with 154 asymmetric pores and progress to the behavior of Toray TGP-H090 carbon papers. The asymmetric laser-drilled sample clearly shows hydraulic admittance measurements are sensitive to sample orientation, especially when examined as a function of saturation state. Finite element modeling of the hydraulic admittance is consistent with experimental measurements. The hydraulic admittance spectra from GDL samples are complex, so we examine trends in the spectra as a function of wet proofing (0% and 40% Teflon loadings) as well as saturation state of the GDL. The presence of clear peaks in the admittance spectra for both GDL samples suggests a few pore types are largely responsible for transporting liquid water.

The effect of asymmetrical sample training on retention functions for hedonic samples in rats

Rats were trained in a symbolic delayed matching-to-sample task to discriminate sample stimuli that consisted of the presence of food or the absence of food. Asymmetrical sample training was provided in which one group was initially trained with only the food sample and the other group was initially trained with only the no-food sample. In addition, within each group half of the rats were trained with an illuminated intertrial interval (ITI) and the remaining rats with a dark ITI. While the retention functions did not differ as a function of which sample was trained first, they did differ as a function of the similarity in the illumination conditions during the ITI and the delay interval. Symmetrical retention functions were obtained when the lighting conditions were similar and slightly asymmetrical retention functions were obtained when the lighting conditions were dissimilar. Probe tests confirmed that features of the no-food sample were attended to and used to generate a memory representation for the no-food sample. The results are not consistent with the hypothesis that asymmetrical sample training encourages coding of the sample introduced initially and default responding to the subsequently introduced sample. Rats generate memory representations for both samples when asymmetrical sample training is given with hedonic samples.

Neural correlates of the perception of contrastive prosodic focus in French: A functional magnetic resonance imaging study

This functional magnetic resonance imaging (fMRI) study aimed at examining the cerebral regions involved in the auditory perception of prosodic focus using a natural focus detection task. Two conditions testing the processing of simple utterances in French were explored, narrow-focused versus broad-focused. Participants performed a correction detection task. The utterances in both conditions had exactly the same segmental, lexical, and syntactic contents, and only differed in their prosodic realization. The comparison between the two conditions therefore allowed us to examine processes strictly associated with prosodic focus processing. To assess the specific effect of pitch on hemispheric specialization, a parametric analysis was conducted using a parameter reflecting pitch variations specifically related to focus. The comparison between the two conditions reveals that brain regions recruited during the detection of contrastive prosodic focus can be described as a right-hemisphere dominant dual network consisting of (a) ventral regions which include the right posterosuperior temporal and bilateral middle temporal gyri and (b) dorsal regions including the bilateral inferior frontal, inferior parietal and left superior parietal gyri. Our results argue for a dual stream model of focus perception compatible with the asymmetric sampling in time hypothesis. They suggest that the detection of prosodic focus involves an interplay between the right and left hemispheres, in which the computation of slowly changing prosodic cues in the right hemisphere dynamically feeds an internal model concurrently used by the left hemisphere, which carries out computations over shorter temporal windows.

Matrix Converter Based on Asymmetric Regular Sampling Method SPWM Control Strategy

In this paper, the Matrix converter can be viewed as AC-DC-AC converter, the asymmetric regular sampling method SPWM control technique is applied in the control of matrix converter, the asymmetric regular sampling method SPWM control strategy of matrix converter, 48 allowed switch combinations and Four-Step Current Commutation method is presented. Based on Matlab/simulink the simulation of the matrix converter with such strategy is carried out. Inductive load simulation is carried out on the matrix converter prototype. The simulation results verify the workability of the asymmetric regular sampling method SPWM strategy for matrix converter.

Cortical oscillations in auditory perception and speech: evidence for two temporal windows in human auditory cortex.

Natural sounds, including vocal communication sounds, contain critical information at multiple time scales. Two essential temporal modulation rates in speech have been argued to be in the low gamma band (∼20–80 ms duration information) and the theta band (∼150–300 ms), corresponding to segmental and diphonic versus syllabic modulation rates, respectively. It has been hypothesized that auditory cortex implements temporal integration using time constants closely related to these values. The neural correlates of a proposed dual temporal window mechanism in human auditory cortex remain poorly understood. We recorded MEG responses from participants listening to non-speech auditory stimuli with different temporal structures, created by concatenating frequency-modulated segments of varied segment durations. We show that such non-speech stimuli with temporal structure matching speech-relevant scales (∼25 and ∼200 ms) elicit reliable phase tracking in the corresponding associated oscillatory frequencies (low gamma and theta bands). In contrast, stimuli with non-matching temporal structure do not. Furthermore, the topography of theta band phase tracking shows rightward lateralization while gamma band phase tracking occurs bilaterally. The results support the hypothesis that there exists multi-time resolution processing in cortex on discontinuous scales and provide evidence for an asymmetric organization of temporal analysis (asymmetrical sampling in time, AST). The data argue for a mesoscopic-level neural mechanism underlying multi-time resolution processing: the sliding and resetting of intrinsic temporal windows on privileged time scales.

Far Field Fluorescence and AFM Superposition with 10nm Special Resolution

We have developed a technique which allows us to determine the location of a fluorescent signal to within 10nm accuracy within a topological scan created by AFM. Imaging topological markers that are both fluorescent and resolvable in an AFM scan, we can triangulate the fluorescence of these markers in conjunction with the fluorescence and topology of a sample to within 10nm accuracy. Here we show data from this method in air as well as wet buffers which are ideal for biological sample measurements. This technique will facilitate localization of fluorescent molecules within asymmetric diffraction limited biological samples.

채널 간 상관관계를 이용한 무손실 컬러 이미지 압축

기존의 무손실 압축은 일반적으로 채널간의 상관관계를 고려하지 않고 각각의 채널을 따로 압축하였다. 채널 간 상관관계를 이용하는 경우도 있으나 이들은 위성/항공 영상과 같은 경우에 제한된 것으로서 일반적인 이미지에 대해서는 만족할만한 성능을 얻지 못하였다. 본 논문에서는 컬러 이미지가 갖는 채널 간의 상관관계를 이용하여 무손실 압축의 성능을 향상시키는 방법을 제안하였다. 제안된 방법에서는 채널 간 상관관계를 표현할 수 있도록 하기 위하여, 비대칭 샘플링을 통해 주어진 영상의 모자이크 이미지를 구성하여 압축을 수행하였고, 압축된 모자이크 이미지의 정보를 이용해서 샘플링되지 않은 나머지 이미지를 예측하여 압축할 정보의 양을 감소시켰다. 제안된 방법은 압축 성능을 평가하는데 일반적으로 사용되는 데이터들에 대해서 채널 간 상관관계를 이용하지 않는 방법에 대해 35%, 채널 간 상관관계를 이용한 기존 방법에 대해 10%의 성능 개선을 보인다. The conventional lossless compression of color images is to apply a compression method to each of color components separately, without considering the channel correlation. There had been several methods that consider the channel correlation, but they were confined to the compression of satellite or aerial images only, and the performance of these algorithms to general photos is not satisfactory. This paper proposes a new lossless color image compression method that exploits the correlation between the color components. Specifically, asymmetric sampling is applied to transform an image into mosaic image and the rest, which are compressed separately. By using the information from the compressed mosaic image, the rest images are predicted for further reducing the information to be compressed. Experimental results show that the proposed method improves the compression performance by 35% over the conventional separate compression methods and 10% over the existing methods that exploit the channel correlation.

Speech processing: From peripheral to hemispheric asymmetry of the auditory system

Language processing from the cochlea to auditory association cortices shows side-dependent specificities with an apparent left hemispheric dominance. The aim of this article was to propose to nonspeech specialists a didactic review of two complementary theories about hemispheric asymmetry in speech processing. Starting from anatomico-physiological and clinical observations of auditory asymmetry and interhemispheric connections, this review then exposes behavioral (dichotic listening paradigm) as well as functional (functional magnetic resonance imaging and positron emission tomography) experiments that assessed hemispheric specialization for speech processing. Even though speech at an early phonological level is regarded as being processed bilaterally, a left-hemispheric dominance exists for higher-level processing. This asymmetry may arise from a segregation of the speech signal, broken apart within nonprimary auditory areas in two distinct temporal integration windows--a fast one on the left and a slower one on the right--modeled through the asymmetric sampling in time theory or a spectro-temporal trade-off, with a higher temporal resolution in the left hemisphere and a higher spectral resolution in the right hemisphere, modeled through the spectral/temporal resolution trade-off theory. Both theories deal with the concept that lower-order tuning principles for acoustic signal might drive higher-order organization for speech processing. However, the precise nature, mechanisms, and origin of speech processing asymmetry are still being debated. Finally, an example of hemispheric asymmetry alteration, which has direct clinical implications, is given through the case of auditory aging that mixes peripheral disorder and modifications of central processing.

Control of Domain-Wall Injection Field with Different Nucleation Pad Geometry

It is experimentally reported herein that the injection field of domain walls (DWs) from the nucleation pad to the nanowire is controlled by the angle of the initializing magnetic field with the use of asymmetric sample structures. The injection field is abruptly varied twice between two distinct values at a certain angle. Micromagnetic simulation is used to model the injection of a DW into the nanowire with respect to the angle of the initializing magnetic field. This is ascribed to the different structure of the DW at the junction between the pad and the nanowire, resulting in the different pinning strength of the DW. These observations provide a way to control the injection field of DWs into nanostructures and give a possibility of the fast, reliable motion of the DW with field strengths less than the so-called Walker field on the nanowire by injecting the DW with a known magnetic structure.

Full Vector Magnetic Field Critical Current Characterization of Coated Conductors Deposited on Solution Deposition Planarized IBAD Templates

Second generation high temperature super-conductor (HTS) wire consists of metal substrate tapes textured with intermediate buffer layers that are coated with a superconducting layer. The applications of these coated conductors require a high current in magnetic fields that are not restricted to a narrow range of angles. Ion beam assisted deposition (IBAD) template tilt, in combination with REBCO vapor deposition, results in asymmetric sample growth. This requires Vector Magnetic Field (VMF) measurement over 180 degrees to be fully described. We have developed a piece wise characterization and analysis method of the VMF using a number of Ic scaling models. Solution Deposition Planarization (SDP) permits REBCO film deposition on 100 nm rms roughness substrates. To test buffer layer effects on film growth, with and without SDP, superconducting films were deposited at Superconductor Technologies, Inc. by co-evaporation of REBCO on IBAD buffer layer templates from Los Alamos. Critical current measurements in VMF up to a magnitude of ~ 0.9 Tesla show behaviors traceable to the effects of buffer layer template on pinning. The ability to discriminate between buffer layers based on in-field Ic behavior is a useful technique for the optimization of buffer layers for future REBCO film deposition.

Effect of bake/cure temperature of an advanced organic ultra low-k material on the interface adhesion strength to metal barriers

The interface adhesion strength of an advanced polymeric low-k material to different metal barriers was quantitatively measured using the four-point bending technique. Different sample configurations were tested in order to find the optimal configuration to study the polymer/barrier interface adhesion strength. The asymmetrical sample configuration with the notch at the film stack side was found to be the most suitable approach to study the adhesion strength of this interface. The effect of bake/cure temperature on the adhesion strength between polymer and barrier was investigated in more detail. Higher cure temperatures resulted in a lower amount of triple C-bonds in the polymer and lower polymer/barrier interface adhesion strength, while no differences in optical and mechanical properties were observed. Moreover, it was found that higher amount of Ta–C bonds formed at the interface improved the polymer/barrier interface adhesion, thereby suggesting that the chemical interaction between the polymer and metal barrier plays a major role in the adhesion performance.

Single-Breathhold Four-Dimensional Assessment of Left Ventricular Morphological and Functional Parameters by Magnetic Resonance Imaging Using the VAST Technique

Introduction:The accurate and reproducible assessment of cardiac volumes, function, and mass is of paramount importance in cardiology. In the present study we sought to determine whether the 3D cine-magnetic resonance (MR) technique, using the variable asymmetric sampling in time (VAST) approach, provided an accurate assessment of LV functional parameters when compared with the conventional 2D cine-MR technique.Methods:A total of 43 consecutive patients referred for a CMR examination for clinical reasons and 14 healthy volunteers were included in the study. Cine images were acquired using a steady-state free precession pulse sequence. Two different multiphase acquisitions were performed: conventional 2D cine-MR and 3D cine-MR. The short-axis cine images acquired by both cine-MR techniques were used for the quantitative assessment of LV end-diastolic, end-systolic and stroke volumes, LV mass and ejection fraction.Results:All CMR examinations were completed successfully, with both cine-MR imaging techniques yielding interpretable diagnostic results in all patients. Regarding the quantitative assessment, Bland-Altman analyses demonstrated a good agreement between the measurements of both cine-MR techniques for all LV parameters. In addition, the agreement between 2D and 3D cine-MR techniques for the qualitative assessment of LV global function was perfect (kappa = 1.0, P<0.001) for the two observers in consensus. The assessment performed by the third independent observer also demonstrated very good agreement (kappa = 0.88, P<0.001).Conclusion:The single breathhold 3D cine-MR technique provides an accurate and reproducible quantitative assessment of LV volumes, mass and function when compared with the conventional 2D cine-MR method.

Determination of spin-orbit coefficients in semiconductor quantum wells

We report the determination of the intrinsic spin-orbit interaction (SOI) parameters for ${\mathrm{In}}_{0.53}{\mathrm{Ga}}_{0.47}\mathrm{As}/{\mathrm{In}}_{0.52}{\mathrm{Al}}_{0.48}\mathrm{As}$ quantum wells (QWs) from the analysis of the weak antilocalization effect. We show that the Dresselhaus SOI is mostly negligible in this system and that the intrinsic parameter for the Rashba effect, ${a}_{\mathrm{SO}}\ensuremath{\equiv}\ensuremath{\alpha}/\ensuremath{\langle}{E}_{z}\ensuremath{\rangle}$, is given to be ${a}_{\mathrm{SO}}{m}^{*}/{m}_{e}=(1.46\ensuremath{-}1.51\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}{N}_{S}$ [m${}^{\ensuremath{-}2}$]) $e{\AA{}}^{2}$, where $\ensuremath{\alpha}$ is the Rashba SOI coefficient, $\ensuremath{\langle}{E}_{z}\ensuremath{\rangle}$ is the expected electric field within the QW, ${m}^{*}/{m}_{e}$ is the electron effective mass ratio, and ${N}_{S}$ is the sheet carrier density. These values for ${a}_{\mathrm{SO}}{m}^{*}$ were also confirmed by the observation of beatings in the Shubnikov--de Haas oscillations in our most asymmetric QW sample.

Optimized density‐weighted imaging for dynamic contrast‐enhanced 3D‐MR mammography

To increase the spatial coverage and to reduce slice crosstalk combined with an optimal signal-to-noise ratio (SNR) in 3D dynamic contrast-enhanced (DCE) magnetic resonance (MR) mammography. Asymmetric sampling schemes and a new reconstruction strategy based on virtual coils are presented for density-weighted (DW) 3D imaging. Additionally, for MR mammography an alternating DW (ADW) sampling along the k(y) direction shifts the undersampling artifacts out of the signal reception region. Virtual coils for effective DW (VIDED) imaging suppresses the aliasing in undersampled DW imaging. VIDED and ADW were compared to the conventional Cartesian imaging in phantom and in vivo MR mammography studies. The slice crosstalk was significantly reduced by VIDED and compared to Cartesian imaging the SNR increased by 16%. Additionally, VIDED and ADW provided a substantially increased field of view (FOV) in the slice direction and allowed the spatial resolution to be improved (up to 60% for ADW and 30% for VIDED) without lengthening the scan time. VIDED and ADW improve the image quality in 3D DCE MR mammography by enhancing the spatial resolution, reducing the slice crosstalk at nearly optimal SNR, and increasing the FOV in the slice direction. For VIDED no lengthening of the scan time or usage of multichannel receiver coils is necessary.

Experimental determination of the Rashba coefficient in InSb/InAlSb quantum wells atzero magnetic field and elevated temperatures

We report the optical measurement of the spin dynamics at elevated temperatures and in zeromagnetic field for two types of degenerately doped n-InSb quantum wells (QWs), one asymmetric(sample A) and one symmetric (sample B) with regards to the electrostatic potential acrossthe QW. Making use of three directly determined experimental parameters: the spin lifetime,τs, the sheet carrierconcentration, n, andthe electron mobility, μ, we directly extract the zero-field spin splitting. For the asymmetric sample where the Rashbainteraction is the dominant source of spin splitting, we deduce a room temperature Rashba parameterof α = 0.09 ± 0.1 eV Å which is in good agreement with calculations and we estimate the Rashba coefficientα0 (a figure of merit for the ease with which electron spins can be modulated via an electricfield). We review the merits/limitations of this approach and the implications of ourfindings for spintronic devices.

Auditory cortex entrainment to syllabic rate in control and dyslexic individuals

Event Abstract Back to Event Auditory cortex entrainment to syllabic rate in control and dyslexic individuals Katia Lehongre1*, Franck Ramus2, Nadège Villiermet2 and Anne-Lise Giraud1 1 LNC INSERM U 960, France 2 LSCP ENS, France Reading difficulties in developmental dyslexia are likely related to a phonological deficit associated with abnormal temporal processing of speech features (Abrams, 2009, Goswami, 2010). According to the asymmetric sampling in time theory (AST, Poeppel, 2003), there is a dominant rapid sampling at gamma rate (25-40Hz) in the left auditiroy cortex and a dominant slow sampling at theta rate (4-7Hz) in the right auditory cortex. This asymmetry is abolished in dyslexics: the lack of left dominant gamma activity appears related to phonological impairments (Lehongre et al. submitted), whereas the lack of right dominance for theta activity seems to be more globally related to reading impairments (Abrams, 2009). To explore the relationship between cortical theta oscillations and reading impairment in dyslexia, we analyzed auditory steady state responses (ASSR) to a sound modulated from 3 to 8 Hz in 10 controls and 10 dyslexics, and correlated them with measures of phonological, verbal memory and reading ability. In normal readers, as predicted by AST we found a dominance of right auditory responses around 4.5 Hz, and an unexpected left dominance around 6 Hz, but no such asymmetry in poor readers. In good readers, ASSR power at 4.5 Hz on the whole cortical surface correlated positively with reading speed within a left lateralized occipito-temporo-frontal network including key regions for reading, e.g. visual word form area (Dehaene, 2001). In dyslexics a correlation was observed in equivalent regions of the right hemisphere for both 4.5 and 6 Hz theta range. While we confirm relevant left hemispheric oscillations in the theta range in normal reading (Gotto, 2010), we find right ones in dyslexics. The precise function of theta oscillations in reading remains to be investigated. Funding: Supported by ANR, FRM. Keywords: Auditory Cortex, Language Conference: XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011. Presentation Type: Poster Presentation Topic: Poster Sessions: Neural Bases of Language Citation: Lehongre K, Ramus F, Villiermet N and Giraud A (2011). Auditory cortex entrainment to syllabic rate in control and dyslexic individuals. Conference Abstract: XI International Conference on Cognitive Neuroscience (ICON XI). doi: 10.3389/conf.fnhum.2011.207.00506 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 22 Nov 2011; Published Online: 28 Nov 2011. * Correspondence: Dr. Katia Lehongre, LNC INSERM U 960, Paris, France, katia.lehongre@ens.fr Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Katia Lehongre Franck Ramus Nadège Villiermet Anne-Lise Giraud Google Katia Lehongre Franck Ramus Nadège Villiermet Anne-Lise Giraud Google Scholar Katia Lehongre Franck Ramus Nadège Villiermet Anne-Lise Giraud PubMed Katia Lehongre Franck Ramus Nadège Villiermet Anne-Lise Giraud Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Two distinct theta rhythms could underlie functional asymmetry of auditory cortices

Event Abstract Back to Event Two distinct theta rhythms could underlie functional asymmetry of auditory cortices Benjamin Morillon1*, Catherine Liegeois-Chauvel2, Luc Arnal3 and Anne-Lise Giraud1 1 Ecole Normale Supérieure, France 2 Université de la Méditerranée, France 3 New York University, United States Poeppel (2003) proposed that left hemispheric dominance in speech processing relies on asymmetric sampling of auditory information. Cortical oscillations in the gamma (~40Hz) and low-theta (~5 Hz) range could be instrumental to this purpose, underpinning phonemic and supra-segmental parsing in left and right auditory cortices, respectively. Yet, whether and how left-hemispheric information sampled at phonemic timescale is re-concatenated into syllabic frames is unaddressed by the theory. Here we present evidence from local field potentials data from an epileptic patient implanted bilaterally in primary (PAC) and secondary (SAC) auditory cortices that two distinct theta ranges operate in right and left auditory cortices. During periods of silence, we observed a peak of energy at 5 Hz in the right auditory cortex and at 8 Hz in the left one. These effects were maximal in SAC. This asymmetric background low and high theta activity was boosted by the presentation of transient tones and syllables. The 8 Hz response in left auditory cortex was accompanied with a low-gamma transient response. Finally, sentences elicited sustained responses in the theta range, with the same 5/8 Hz asymmetrical pattern. We thus confirm that low-theta rhythm (5 Hz) is right-dominant both at rest (Giraud et al., 2007) and during speech processing (Abrams et al., 2008), but additionally show the presence of a parallel high-theta rhythm (8 Hz) in left auditory cortex. Its predominance in left SAC relative to PAC, where gamma rhythm is more strongly expressed (Morillon et al., 2010; Giraud et al., 2007) could reflect that it integrates information from the latter into syllabic frames to guide further processing stages. The role of this specific rhythm (Mo et al., 2011) needs to be further explored. Keywords: cortical oscillations, Intra-cranial Electrophysiology Conference: XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011. Presentation Type: Poster Presentation Topic: Abstracts Citation: Morillon B, Liegeois-Chauvel C, Arnal L and Giraud A (2011). Two distinct theta rhythms could underlie functional asymmetry of auditory cortices. Conference Abstract: XI International Conference on Cognitive Neuroscience (ICON XI). doi: 10.3389/conf.fnhum.2011.207.00063 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 15 Nov 2011; Published Online: 25 Nov 2011. * Correspondence: Dr. Benjamin Morillon, Ecole Normale Supérieure, Paris, France, bnmorillon@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Benjamin Morillon Catherine Liegeois-Chauvel Luc Arnal Anne-Lise Giraud Google Benjamin Morillon Catherine Liegeois-Chauvel Luc Arnal Anne-Lise Giraud Google Scholar Benjamin Morillon Catherine Liegeois-Chauvel Luc Arnal Anne-Lise Giraud PubMed Benjamin Morillon Catherine Liegeois-Chauvel Luc Arnal Anne-Lise Giraud Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.