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Robert J Zatorre – One of the best experts on this subject based on the ideXlab platform.

  • spectro temporal Modulation transfer function of single voxels in the human auditory cortex measured with high resolution fmri
    Proceedings of the National Academy of Sciences of the United States of America, 2009
    Co-Authors: Marc Schonwiesner, Robert J Zatorre
    Abstract:

    Are visual and auditory stimuli processed by similar mechanisms in the human cerebral cortex? Images can be thought of as light energy Modulations over two spatial dimensions, and low-level visual areas analyze images by decomposition into spatial frequencies. Similarly, sounds are energy Modulations over time and frequency, and they can be identified and discriminated by the content of such Modulations. An obvious question is therefore whether human auditory areas, in direct analogy to visual areas, represent the spectro-temporal Modulation content of acoustic stimuli. To answer this question, we measured spectro-temporal Modulation transfer functions of single voxels in the human auditory cortex with functional magnetic resonance imaging. We presented dynamic ripples, complex broadband stimuli with a drifting sinusoidal spectral envelope. Dynamic ripples are the auditory equivalent of the gratings often used in studies of the visual system. We demonstrate selective tuning to combined spectro-temporal Modulations in the primary and secondary auditory cortex. We describe several types of Modulation transfer functions, extracting different spectro-temporal features, with a high degree of interaction between spectral and temporal parameters. The overall low-pass Modulation rate preference of the cortex matches the Modulation content of natural sounds. These results demonstrate that combined spectro-temporal Modulations are represented in the human auditory cortex, and suggest that complex signals are decomposed and processed according to their Modulation content, the same transformation used by the visual system.

Frederic E Theunissen – One of the best experts on this subject based on the ideXlab platform.

  • the Modulation transfer function for speech intelligibility
    PLOS Computational Biology, 2009
    Co-Authors: Taffeta M Elliott, Frederic E Theunissen
    Abstract:

    We systematically determined which spectrotemporal Modulations in speech are necessary for comprehension by human listeners. Speech comprehension has been shown to be robust to spectral and temporal degradations, but the specific relevance of particular degradations is arguable due to the complexity of the joint spectral and temporal information in the speech signal. We applied a novel Modulation filtering technique to recorded sentences to restrict acoustic information quantitatively and to obtain a joint spectrotemporal Modulation transfer function for speech comprehension, the speech MTF. For American English, the speech MTF showed the criticality of low Modulation frequencies in both time and frequency. Comprehension was significantly impaired when temporal Modulations <12 Hz or spectral Modulations <4 cycles/kHz were removed. More specifically, the MTF was bandpass in temporal Modulations and low-pass in spectral Modulations: temporal Modulations from 1 to 7 Hz and spectral Modulations <1 cycles/kHz were the most important. We evaluated the importance of spectrotemporal Modulations for vocal gender identification and found a different region of interest: removing spectral Modulations between 3 and 7 cycles/kHz significantly increases gender misidentifications of female speakers. The determination of the speech MTF furnishes an additional method for producing speech signals with reduced bandwidth but high intelligibility. Such compression could be used for audio applications such as file compression or noise removal and for clinical applications such as signal processing for cochlear implants.

Akbari Alireza – One of the best experts on this subject based on the ideXlab platform.

  • Strain-induced stripe phase in charge ordered single layer NbSe$_2$
    'Springer Science and Business Media LLC', 2020
    Co-Authors: Cossu Fabrizio, Palotas Krisztia, Sarka Saga, Di Marco Igo, Akbari Alireza
    Abstract:

    Charge density waves are ubiquitous phenomena in metallic transition metal dichalcogenides. In NbSe$_2$, a triangular $3\times3$ structural Modulation is coupled to a charge Modulation. Recent experiments reported evidence for a triangular-stripe transition at the surface, due to strain or accidental doping and associated to a $4\times4$ Modulation. We employ \textit{ab-initio} calculations to investigate the strain-induced structural instabilities in a pristine single layer and analyse the energy hierarchy of the structural and charge Modulations. Our results support the observation of phase separation between triangular and stripe phases in 1H-NbSe$_2$, relating the stripe phase to compressive isotropic strain, favouring the $4\times4$ Modulation. The observed wavelength of the charge Modulation is also reproduced with good accuracy

  • Strain-induced stripe phase in charge-ordered single layer NbSe2
    'Springer Science and Business Media LLC', 2020
    Co-Authors: Cossu Fabrizio, Palotas Krisztia, Sarka Saga, Di Marco Igo, Akbari Alireza
    Abstract:

    Charge density waves are ubiquitous phenomena in metallic transition metal dichalcogenides. In NbSe2, a triangular 3×3 structural Modulation is coupled to a charge Modulation. Recent experiments reported evidence for a triangular-stripe transition at the surface, due to strain or accidental doping and associated to a 4×4 Modulation. We employ ab initio calculations to investigate the strain-induced structural instabilities in a pristine single layer and analyse the energy hierarchy of the structural and charge Modulations. Our results support the observation of phase separation between triangular and stripe phases in 1H-NbSe2, relating the stripe phase to compressive isotropic strain, favouring the 4×4 Modulation. The observed wavelength of the charge Modulation is also reproduced with a good accuracy

Marc Schonwiesner – One of the best experts on this subject based on the ideXlab platform.

  • spectro temporal Modulation transfer function of single voxels in the human auditory cortex measured with high resolution fmri
    Proceedings of the National Academy of Sciences of the United States of America, 2009
    Co-Authors: Marc Schonwiesner, Robert J Zatorre
    Abstract:

    Are visual and auditory stimuli processed by similar mechanisms in the human cerebral cortex? Images can be thought of as light energy Modulations over two spatial dimensions, and low-level visual areas analyze images by decomposition into spatial frequencies. Similarly, sounds are energy Modulations over time and frequency, and they can be identified and discriminated by the content of such Modulations. An obvious question is therefore whether human auditory areas, in direct analogy to visual areas, represent the spectro-temporal Modulation content of acoustic stimuli. To answer this question, we measured spectro-temporal Modulation transfer functions of single voxels in the human auditory cortex with functional magnetic resonance imaging. We presented dynamic ripples, complex broadband stimuli with a drifting sinusoidal spectral envelope. Dynamic ripples are the auditory equivalent of the gratings often used in studies of the visual system. We demonstrate selective tuning to combined spectro-temporal Modulations in the primary and secondary auditory cortex. We describe several types of Modulation transfer functions, extracting different spectro-temporal features, with a high degree of interaction between spectral and temporal parameters. The overall low-pass Modulation rate preference of the cortex matches the Modulation content of natural sounds. These results demonstrate that combined spectro-temporal Modulations are represented in the human auditory cortex, and suggest that complex signals are decomposed and processed according to their Modulation content, the same transformation used by the visual system.

Cossu Fabrizio – One of the best experts on this subject based on the ideXlab platform.

  • Strain-induced stripe phase in charge ordered single layer NbSe$_2$
    'Springer Science and Business Media LLC', 2020
    Co-Authors: Cossu Fabrizio, Palotas Krisztia, Sarka Saga, Di Marco Igo, Akbari Alireza
    Abstract:

    Charge density waves are ubiquitous phenomena in metallic transition metal dichalcogenides. In NbSe$_2$, a triangular $3\times3$ structural Modulation is coupled to a charge Modulation. Recent experiments reported evidence for a triangular-stripe transition at the surface, due to strain or accidental doping and associated to a $4\times4$ Modulation. We employ \textit{ab-initio} calculations to investigate the strain-induced structural instabilities in a pristine single layer and analyse the energy hierarchy of the structural and charge Modulations. Our results support the observation of phase separation between triangular and stripe phases in 1H-NbSe$_2$, relating the stripe phase to compressive isotropic strain, favouring the $4\times4$ Modulation. The observed wavelength of the charge Modulation is also reproduced with good accuracy

  • Strain-induced stripe phase in charge-ordered single layer NbSe2
    'Springer Science and Business Media LLC', 2020
    Co-Authors: Cossu Fabrizio, Palotas Krisztia, Sarka Saga, Di Marco Igo, Akbari Alireza
    Abstract:

    Charge density waves are ubiquitous phenomena in metallic transition metal dichalcogenides. In NbSe2, a triangular 3×3 structural Modulation is coupled to a charge Modulation. Recent experiments reported evidence for a triangular-stripe transition at the surface, due to strain or accidental doping and associated to a 4×4 Modulation. We employ ab initio calculations to investigate the strain-induced structural instabilities in a pristine single layer and analyse the energy hierarchy of the structural and charge Modulations. Our results support the observation of phase separation between triangular and stripe phases in 1H-NbSe2, relating the stripe phase to compressive isotropic strain, favouring the 4×4 Modulation. The observed wavelength of the charge Modulation is also reproduced with a good accuracy