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Thomas J. Imig - One of the best experts on this subject based on the ideXlab platform.

  • directionality derived from differential sensitivity to monaural and binaural cues in the cat s medial geniculate body
    Journal of Neurophysiology, 2000
    Co-Authors: Frank K. Samson, Janine C. Clarey, Pascal Barone, Andrew W Irons, Pierre Poirier, Thomas J. Imig
    Abstract:

    Azimuth tuning of high-frequency neurons in the primary auditory cortex (AI) is known to depend on binaural disparity and monaural spectral (pinna) cues present in broadband noise bursts. Single-unit response patterns differ according to binaural interactions, strength of monaural excitatory input from each ear, and Azimuth sensitivity to monaural stimulation. The latter characteristic has been used as a gauge of neural sensitivity to monaural spectral directional cues. Azimuth sensitivity may depend predominantly on binaural disparity cues, exclusively on monaural spectral cues, or on both. The primary goal of this study was to determine whether each cortical response pattern corresponds to a similar pattern in the medial geniculate body (MGB) or whether some patterns are unique to the cortex. Single-unit responses were recorded from the ventral nucleus (Vn) and lateral part of the posterior group of thalamic nuclei (Po), tonotopic subdivisions of the MGB. Responses to free-field presentation of noise bursts that varied in Azimuth and sound pressure level were obtained using methods identical to those used previously in field AI. Many units were Azimuth sensitive, i.e., they responded well at some Azimuths, and poorly, if at all, at others. These were studied further by obtaining responses to monaural noise stimulation, approximated by reversible plugging of one ear. Monaural directional (MD) cells were sensitive to the Azimuth of monaural noise stimulation, whereas binaural directional (BD) cells were either insensitive to its Azimuth or monaurally unresponsive. Thus BD and MD cells show differential sensitivity to monaural spectral cues. Monaural Azimuth sensitivity could not be used to interpret the spectral sensitivity of predominantly binaural cells that exhibited strong binaural facilitation because they were either unresponsive or poorly responsive to monaural stimulation. The available evidence suggests that some such cells are sensitive to spectral cues. The results do not indicate the presence of any response types in AI that are not present in the MGB. Vn and Po contain similar classes of MD and BD cells. Because Po neurons project to the anterior auditory field, neurons in this cortical area also are likely to exhibit differential sensitivity to binaural disparity and monaural spectral cues. Comparison of these MGB data with a published report of cochlear nucleus (CN) single-unit Azimuth tuning shows that MGB sensitivity to spectral cues is considerably stronger than CN sensitivity.

  • Effects of ear plugging on single-unit Azimuth sensitivity in cat primary auditory cortex. II. Azimuth tuning dependent upon binaural stimulation.
    Journal of neurophysiology, 1994
    Co-Authors: Frank K. Samson, Janine C. Clarey, Pascal Barone, Thomas J. Imig
    Abstract:

    1. Single-unit recordings were carried out in primary auditory cortex (AI) of barbiturate-anesthetized cats. Observations were based on a sample of 131 high-best-frequency (> 5 kHz), Azimuth-sensitive neurons. These were identified by their responses to a set of noise bursts, presented in the free field, that varied in Azimuth and sound-pressure level (SPL). Each Azimuth-sensitive neuron responded well to some levels at certain Azimuths, but did not respond well to any level at other Azimuths. 2. Unilateral ear plugging was used to infer each neuron's response to monaural stimulation. Ear plugs, produced by injecting a plastic ear mold compound into the external ear, attenuated sound reaching the tympanic membrane by 25-70 dB. The Azimuth tuning of a large proportion of the sample (62/131), referred to as binaural directional (BD), was completely dependent upon binaural stimulation because with one ear plugged, these cells were insensitive to Azimuth (either responded well at all Azimuths or failed to respond at any Azimuth) or in a few cases exhibited striking changes in location of Azimuth function peaks. This report describes patterns of monaural responses and binaural interactions exhibited by BD neurons and relates them to each cell's Azimuth and level tuning. The response of BD cells to ear plugging is consistent with the hypothesis that they derive Azimuth tuning from interaural level differences present in noise bursts. Another component of the sample consisted of monaural directional (27/131) cells that derived Azimuth tuning in part or entirely from monaural spectral cues. Cells in the remaining portion of the sample (42/131) responded too unreliably to permit specific conclusions. 3. Binaural interactions were inferred by statistical comparison of a cell's responses to monaural (unilateral plug) and binaural (no plug) stimulation. A larger binaural response than either monaural response was taken as evidence for binaural facilitation. A smaller binaural than monaural response was taken as evidence for binaural inhibition. Binaural facilitation was exhibited by 65% (40/62) of the BD sample (facilitatory cells). Many of these exhibited mixed interactions, i.e., binaural facilitation occurred in response to some Azimuth-level combinations, and binaural inhibition to others. Binaural inhibition in the absence of binaural facilitation occurred in 35% (22/62) of the BD sample, a majority of which were EI cells, so called because they received excitatory (E) input from one ear (excitatory ear) and inhibitory (I) input from the other (inhibitory ear). One cell that exhibited binaural inhibition received excitatory input from each ear.(ABSTRACT TRUNCATED AT 400 WORDS)

  • Effects of ear plugging on single-unit Azimuth sensitivity in cat primary auditory cortex. I. Evidence for monaural directional cues.
    Journal of neurophysiology, 1993
    Co-Authors: Frank K. Samson, Janine C. Clarey, Pascal Barone, Thomas J. Imig
    Abstract:

    1. Single-unit recordings were carried out in primary auditory cortex (AI) of barbiturate-anesthetized cats. Neurons, sensitive to sound direction in the horizontal plane (Azimuth), were identified by their responses to noise bursts, presented in the free field, that varied in Azimuth and sound pressure level (SPL). SPLs typically varied between 0 and 80 dB and were presented at each Azimuth that was tested. Each Azimuth-sensitive neuron responded well to some SPLs at certain Azimuths and did not respond well to any SPL at other Azimuths. This report describes AI neurons that were sensitive to the Azimuth of monaurally presented noise bursts. 2. Unilateral ear plugging was used to test each Azimuth-sensitive neuron's response to monaural stimulation. Ear plugs, produced by injecting a plastic ear mold compound into the concha and ear canal, attenuated sound reaching the tympanic membrane by 25-70 dB. Binaural interactions were inferred by comparing responses obtained under binaural (no plug) and monaural (ear plug) conditions. 3. Of the total sample of 131 Azimuth-sensitive cells whose responses to ear plugging were studied, 27 were sensitive to the Azimuth of monaurally presented noise bursts. We refer to these as monaural directional (MD) cells, and this report describes their properties. The remainder of the sample consisted of cells that either required binaural stimulation for Azimuth sensitivity (63/131), because they were insensitive to Azimuth under unilateral ear plug conditions or responded too unreliably to permit detailed conclusions regarding the effect of ear plugging (41/131). 4. Most (25/27) MD cells received either monaural input (MD-E0) or binaural excitatory/inhibitory input (MD-EI), as inferred from ear plugging. Two MD cells showed other characteristics. The contralateral ear was excitatory for 25/27 MD cells. 5. MD-E0 cells (22%, 6/27) were monaural. They were unaffected by unilateral ear plugging, showing that they received excitatory input from one ear, and that stimulation of the other ear was without apparent effect. On the other hand, some monaural cells in AI were insensitive to the Azimuth of noise bursts, showing that sensitivity to monaural directional cues is not a property of all monaural cells in AI. 6. MD-EI cells (70%, 19/27) exhibited an increase in responsiveness on the side of the plugged ear, showing that they received excitatory drive from one ear and inhibitory drive from the other. MD-EI cells remained Azimuth sensitive with the inhibitory ear plugged, showing that they were sensitive to monaural directional cues at the excitatory ear.(ABSTRACT TRUNCATED AT 400 WORDS)

Frank K. Samson - One of the best experts on this subject based on the ideXlab platform.

  • directionality derived from differential sensitivity to monaural and binaural cues in the cat s medial geniculate body
    Journal of Neurophysiology, 2000
    Co-Authors: Frank K. Samson, Janine C. Clarey, Pascal Barone, Andrew W Irons, Pierre Poirier, Thomas J. Imig
    Abstract:

    Azimuth tuning of high-frequency neurons in the primary auditory cortex (AI) is known to depend on binaural disparity and monaural spectral (pinna) cues present in broadband noise bursts. Single-unit response patterns differ according to binaural interactions, strength of monaural excitatory input from each ear, and Azimuth sensitivity to monaural stimulation. The latter characteristic has been used as a gauge of neural sensitivity to monaural spectral directional cues. Azimuth sensitivity may depend predominantly on binaural disparity cues, exclusively on monaural spectral cues, or on both. The primary goal of this study was to determine whether each cortical response pattern corresponds to a similar pattern in the medial geniculate body (MGB) or whether some patterns are unique to the cortex. Single-unit responses were recorded from the ventral nucleus (Vn) and lateral part of the posterior group of thalamic nuclei (Po), tonotopic subdivisions of the MGB. Responses to free-field presentation of noise bursts that varied in Azimuth and sound pressure level were obtained using methods identical to those used previously in field AI. Many units were Azimuth sensitive, i.e., they responded well at some Azimuths, and poorly, if at all, at others. These were studied further by obtaining responses to monaural noise stimulation, approximated by reversible plugging of one ear. Monaural directional (MD) cells were sensitive to the Azimuth of monaural noise stimulation, whereas binaural directional (BD) cells were either insensitive to its Azimuth or monaurally unresponsive. Thus BD and MD cells show differential sensitivity to monaural spectral cues. Monaural Azimuth sensitivity could not be used to interpret the spectral sensitivity of predominantly binaural cells that exhibited strong binaural facilitation because they were either unresponsive or poorly responsive to monaural stimulation. The available evidence suggests that some such cells are sensitive to spectral cues. The results do not indicate the presence of any response types in AI that are not present in the MGB. Vn and Po contain similar classes of MD and BD cells. Because Po neurons project to the anterior auditory field, neurons in this cortical area also are likely to exhibit differential sensitivity to binaural disparity and monaural spectral cues. Comparison of these MGB data with a published report of cochlear nucleus (CN) single-unit Azimuth tuning shows that MGB sensitivity to spectral cues is considerably stronger than CN sensitivity.

  • Effects of ear plugging on single-unit Azimuth sensitivity in cat primary auditory cortex. II. Azimuth tuning dependent upon binaural stimulation.
    Journal of neurophysiology, 1994
    Co-Authors: Frank K. Samson, Janine C. Clarey, Pascal Barone, Thomas J. Imig
    Abstract:

    1. Single-unit recordings were carried out in primary auditory cortex (AI) of barbiturate-anesthetized cats. Observations were based on a sample of 131 high-best-frequency (> 5 kHz), Azimuth-sensitive neurons. These were identified by their responses to a set of noise bursts, presented in the free field, that varied in Azimuth and sound-pressure level (SPL). Each Azimuth-sensitive neuron responded well to some levels at certain Azimuths, but did not respond well to any level at other Azimuths. 2. Unilateral ear plugging was used to infer each neuron's response to monaural stimulation. Ear plugs, produced by injecting a plastic ear mold compound into the external ear, attenuated sound reaching the tympanic membrane by 25-70 dB. The Azimuth tuning of a large proportion of the sample (62/131), referred to as binaural directional (BD), was completely dependent upon binaural stimulation because with one ear plugged, these cells were insensitive to Azimuth (either responded well at all Azimuths or failed to respond at any Azimuth) or in a few cases exhibited striking changes in location of Azimuth function peaks. This report describes patterns of monaural responses and binaural interactions exhibited by BD neurons and relates them to each cell's Azimuth and level tuning. The response of BD cells to ear plugging is consistent with the hypothesis that they derive Azimuth tuning from interaural level differences present in noise bursts. Another component of the sample consisted of monaural directional (27/131) cells that derived Azimuth tuning in part or entirely from monaural spectral cues. Cells in the remaining portion of the sample (42/131) responded too unreliably to permit specific conclusions. 3. Binaural interactions were inferred by statistical comparison of a cell's responses to monaural (unilateral plug) and binaural (no plug) stimulation. A larger binaural response than either monaural response was taken as evidence for binaural facilitation. A smaller binaural than monaural response was taken as evidence for binaural inhibition. Binaural facilitation was exhibited by 65% (40/62) of the BD sample (facilitatory cells). Many of these exhibited mixed interactions, i.e., binaural facilitation occurred in response to some Azimuth-level combinations, and binaural inhibition to others. Binaural inhibition in the absence of binaural facilitation occurred in 35% (22/62) of the BD sample, a majority of which were EI cells, so called because they received excitatory (E) input from one ear (excitatory ear) and inhibitory (I) input from the other (inhibitory ear). One cell that exhibited binaural inhibition received excitatory input from each ear.(ABSTRACT TRUNCATED AT 400 WORDS)

  • Effects of ear plugging on single-unit Azimuth sensitivity in cat primary auditory cortex. I. Evidence for monaural directional cues.
    Journal of neurophysiology, 1993
    Co-Authors: Frank K. Samson, Janine C. Clarey, Pascal Barone, Thomas J. Imig
    Abstract:

    1. Single-unit recordings were carried out in primary auditory cortex (AI) of barbiturate-anesthetized cats. Neurons, sensitive to sound direction in the horizontal plane (Azimuth), were identified by their responses to noise bursts, presented in the free field, that varied in Azimuth and sound pressure level (SPL). SPLs typically varied between 0 and 80 dB and were presented at each Azimuth that was tested. Each Azimuth-sensitive neuron responded well to some SPLs at certain Azimuths and did not respond well to any SPL at other Azimuths. This report describes AI neurons that were sensitive to the Azimuth of monaurally presented noise bursts. 2. Unilateral ear plugging was used to test each Azimuth-sensitive neuron's response to monaural stimulation. Ear plugs, produced by injecting a plastic ear mold compound into the concha and ear canal, attenuated sound reaching the tympanic membrane by 25-70 dB. Binaural interactions were inferred by comparing responses obtained under binaural (no plug) and monaural (ear plug) conditions. 3. Of the total sample of 131 Azimuth-sensitive cells whose responses to ear plugging were studied, 27 were sensitive to the Azimuth of monaurally presented noise bursts. We refer to these as monaural directional (MD) cells, and this report describes their properties. The remainder of the sample consisted of cells that either required binaural stimulation for Azimuth sensitivity (63/131), because they were insensitive to Azimuth under unilateral ear plug conditions or responded too unreliably to permit detailed conclusions regarding the effect of ear plugging (41/131). 4. Most (25/27) MD cells received either monaural input (MD-E0) or binaural excitatory/inhibitory input (MD-EI), as inferred from ear plugging. Two MD cells showed other characteristics. The contralateral ear was excitatory for 25/27 MD cells. 5. MD-E0 cells (22%, 6/27) were monaural. They were unaffected by unilateral ear plugging, showing that they received excitatory input from one ear, and that stimulation of the other ear was without apparent effect. On the other hand, some monaural cells in AI were insensitive to the Azimuth of noise bursts, showing that sensitivity to monaural directional cues is not a property of all monaural cells in AI. 6. MD-EI cells (70%, 19/27) exhibited an increase in responsiveness on the side of the plugged ear, showing that they received excitatory drive from one ear and inhibitory drive from the other. MD-EI cells remained Azimuth sensitive with the inhibitory ear plugged, showing that they were sensitive to monaural directional cues at the excitatory ear.(ABSTRACT TRUNCATED AT 400 WORDS)

Hanwei Zhang - One of the best experts on this subject based on the ideXlab platform.

  • constructing an observational model of the neutral atmospheric refraction delay from measured values of the astronomical refraction
    The Astronomical Journal, 2007
    Co-Authors: Wei Mao, Lei Yang, Qiong-xian Tie, Hanwei Zhang
    Abstract:

    Discussing the requirements for an accurate correction of the neutral atmospheric refraction delay for the Global Positioning System, our paper points out that the existing theoretical correction models and the old postprocessing methods cannot attain the anticipated accuracy because the atmospheric refraction index has not been directly determined precisely. It is necessary to adopt atmospheric refraction delay models to improve the correction accuracy. The models are dependent on the observing station and the observation Azimuth. By the new method we propose in this paper, the observational data of astronomical refractions at different Azimuths and different zenith distances are grouped according to Azimuth and used to calculate the refractivity and mapping functions. As an example of the newmethod, we introduce the configuration of the Lower Latitude Meridian Circle and the measurement method of instantaneous astronomical refractions, and present the observational astronomical refraction model toward the east, south, west, and north of the Yunnan Observatory. We estimate that, without the use of any atmospheric distribution models, the correction accuracy of the zenith delay will be within 1 mm, the correction accuracy of the refraction delay at the lower elevation will be improved to a centimeter magnitude, and the cutoff elevation angle will be reduced to 5 degrees or less.

  • a possible means of improving the accuracy of refraction delay correction of neutral atmosphere
    Chinese Astronomy and Astrophysics, 2007
    Co-Authors: Hanwei Zhang, Binhua Li, Lei Yang
    Abstract:

    Abstract The space geodetic technology requires an accurate model of correction of refraction delay by the neutral atmosphere that varies from one observing station to another, and from one Azimuth to the next. It is pointed out that under the present condition the astronomical refraction can not yet be directly determined, any correction model because of its high dependence on the assumed atmospheric distribution, is incapable of achieving the required accuracy or of improving the cut-off altitude. In this paper, based on the special properties of the lower latitude meridian circle at Yunnan Observatory and our experience of determining atmospheric refraction therewith, a new method is proposed for improving the accuracy of refraction delay correction. Namely, the measured data of astronomical refraction of an observing station from near zenith to low altitudes in different Azimuths are used to evaluate the refractivities and the parameters of the mapping functions, thereby establishing a model of atmospheric refraction delay correction that varies with the observing station and the Azimuth. Since it is unnecessary for the new method to adopt any atmospheric distribution model, application of this new method will improve correction accuracy of refraction delay to better than 1mm at zenith and to centimeters at low altitudes, and improve the cut-off altitude to below 5 degrees.

Pascal Barone - One of the best experts on this subject based on the ideXlab platform.

  • directionality derived from differential sensitivity to monaural and binaural cues in the cat s medial geniculate body
    Journal of Neurophysiology, 2000
    Co-Authors: Frank K. Samson, Janine C. Clarey, Pascal Barone, Andrew W Irons, Pierre Poirier, Thomas J. Imig
    Abstract:

    Azimuth tuning of high-frequency neurons in the primary auditory cortex (AI) is known to depend on binaural disparity and monaural spectral (pinna) cues present in broadband noise bursts. Single-unit response patterns differ according to binaural interactions, strength of monaural excitatory input from each ear, and Azimuth sensitivity to monaural stimulation. The latter characteristic has been used as a gauge of neural sensitivity to monaural spectral directional cues. Azimuth sensitivity may depend predominantly on binaural disparity cues, exclusively on monaural spectral cues, or on both. The primary goal of this study was to determine whether each cortical response pattern corresponds to a similar pattern in the medial geniculate body (MGB) or whether some patterns are unique to the cortex. Single-unit responses were recorded from the ventral nucleus (Vn) and lateral part of the posterior group of thalamic nuclei (Po), tonotopic subdivisions of the MGB. Responses to free-field presentation of noise bursts that varied in Azimuth and sound pressure level were obtained using methods identical to those used previously in field AI. Many units were Azimuth sensitive, i.e., they responded well at some Azimuths, and poorly, if at all, at others. These were studied further by obtaining responses to monaural noise stimulation, approximated by reversible plugging of one ear. Monaural directional (MD) cells were sensitive to the Azimuth of monaural noise stimulation, whereas binaural directional (BD) cells were either insensitive to its Azimuth or monaurally unresponsive. Thus BD and MD cells show differential sensitivity to monaural spectral cues. Monaural Azimuth sensitivity could not be used to interpret the spectral sensitivity of predominantly binaural cells that exhibited strong binaural facilitation because they were either unresponsive or poorly responsive to monaural stimulation. The available evidence suggests that some such cells are sensitive to spectral cues. The results do not indicate the presence of any response types in AI that are not present in the MGB. Vn and Po contain similar classes of MD and BD cells. Because Po neurons project to the anterior auditory field, neurons in this cortical area also are likely to exhibit differential sensitivity to binaural disparity and monaural spectral cues. Comparison of these MGB data with a published report of cochlear nucleus (CN) single-unit Azimuth tuning shows that MGB sensitivity to spectral cues is considerably stronger than CN sensitivity.

  • Effects of ear plugging on single-unit Azimuth sensitivity in cat primary auditory cortex. II. Azimuth tuning dependent upon binaural stimulation.
    Journal of neurophysiology, 1994
    Co-Authors: Frank K. Samson, Janine C. Clarey, Pascal Barone, Thomas J. Imig
    Abstract:

    1. Single-unit recordings were carried out in primary auditory cortex (AI) of barbiturate-anesthetized cats. Observations were based on a sample of 131 high-best-frequency (> 5 kHz), Azimuth-sensitive neurons. These were identified by their responses to a set of noise bursts, presented in the free field, that varied in Azimuth and sound-pressure level (SPL). Each Azimuth-sensitive neuron responded well to some levels at certain Azimuths, but did not respond well to any level at other Azimuths. 2. Unilateral ear plugging was used to infer each neuron's response to monaural stimulation. Ear plugs, produced by injecting a plastic ear mold compound into the external ear, attenuated sound reaching the tympanic membrane by 25-70 dB. The Azimuth tuning of a large proportion of the sample (62/131), referred to as binaural directional (BD), was completely dependent upon binaural stimulation because with one ear plugged, these cells were insensitive to Azimuth (either responded well at all Azimuths or failed to respond at any Azimuth) or in a few cases exhibited striking changes in location of Azimuth function peaks. This report describes patterns of monaural responses and binaural interactions exhibited by BD neurons and relates them to each cell's Azimuth and level tuning. The response of BD cells to ear plugging is consistent with the hypothesis that they derive Azimuth tuning from interaural level differences present in noise bursts. Another component of the sample consisted of monaural directional (27/131) cells that derived Azimuth tuning in part or entirely from monaural spectral cues. Cells in the remaining portion of the sample (42/131) responded too unreliably to permit specific conclusions. 3. Binaural interactions were inferred by statistical comparison of a cell's responses to monaural (unilateral plug) and binaural (no plug) stimulation. A larger binaural response than either monaural response was taken as evidence for binaural facilitation. A smaller binaural than monaural response was taken as evidence for binaural inhibition. Binaural facilitation was exhibited by 65% (40/62) of the BD sample (facilitatory cells). Many of these exhibited mixed interactions, i.e., binaural facilitation occurred in response to some Azimuth-level combinations, and binaural inhibition to others. Binaural inhibition in the absence of binaural facilitation occurred in 35% (22/62) of the BD sample, a majority of which were EI cells, so called because they received excitatory (E) input from one ear (excitatory ear) and inhibitory (I) input from the other (inhibitory ear). One cell that exhibited binaural inhibition received excitatory input from each ear.(ABSTRACT TRUNCATED AT 400 WORDS)

  • Effects of ear plugging on single-unit Azimuth sensitivity in cat primary auditory cortex. I. Evidence for monaural directional cues.
    Journal of neurophysiology, 1993
    Co-Authors: Frank K. Samson, Janine C. Clarey, Pascal Barone, Thomas J. Imig
    Abstract:

    1. Single-unit recordings were carried out in primary auditory cortex (AI) of barbiturate-anesthetized cats. Neurons, sensitive to sound direction in the horizontal plane (Azimuth), were identified by their responses to noise bursts, presented in the free field, that varied in Azimuth and sound pressure level (SPL). SPLs typically varied between 0 and 80 dB and were presented at each Azimuth that was tested. Each Azimuth-sensitive neuron responded well to some SPLs at certain Azimuths and did not respond well to any SPL at other Azimuths. This report describes AI neurons that were sensitive to the Azimuth of monaurally presented noise bursts. 2. Unilateral ear plugging was used to test each Azimuth-sensitive neuron's response to monaural stimulation. Ear plugs, produced by injecting a plastic ear mold compound into the concha and ear canal, attenuated sound reaching the tympanic membrane by 25-70 dB. Binaural interactions were inferred by comparing responses obtained under binaural (no plug) and monaural (ear plug) conditions. 3. Of the total sample of 131 Azimuth-sensitive cells whose responses to ear plugging were studied, 27 were sensitive to the Azimuth of monaurally presented noise bursts. We refer to these as monaural directional (MD) cells, and this report describes their properties. The remainder of the sample consisted of cells that either required binaural stimulation for Azimuth sensitivity (63/131), because they were insensitive to Azimuth under unilateral ear plug conditions or responded too unreliably to permit detailed conclusions regarding the effect of ear plugging (41/131). 4. Most (25/27) MD cells received either monaural input (MD-E0) or binaural excitatory/inhibitory input (MD-EI), as inferred from ear plugging. Two MD cells showed other characteristics. The contralateral ear was excitatory for 25/27 MD cells. 5. MD-E0 cells (22%, 6/27) were monaural. They were unaffected by unilateral ear plugging, showing that they received excitatory input from one ear, and that stimulation of the other ear was without apparent effect. On the other hand, some monaural cells in AI were insensitive to the Azimuth of noise bursts, showing that sensitivity to monaural directional cues is not a property of all monaural cells in AI. 6. MD-EI cells (70%, 19/27) exhibited an increase in responsiveness on the side of the plugged ear, showing that they received excitatory drive from one ear and inhibitory drive from the other. MD-EI cells remained Azimuth sensitive with the inhibitory ear plugged, showing that they were sensitive to monaural directional cues at the excitatory ear.(ABSTRACT TRUNCATED AT 400 WORDS)

Janine C. Clarey - One of the best experts on this subject based on the ideXlab platform.

  • directionality derived from differential sensitivity to monaural and binaural cues in the cat s medial geniculate body
    Journal of Neurophysiology, 2000
    Co-Authors: Frank K. Samson, Janine C. Clarey, Pascal Barone, Andrew W Irons, Pierre Poirier, Thomas J. Imig
    Abstract:

    Azimuth tuning of high-frequency neurons in the primary auditory cortex (AI) is known to depend on binaural disparity and monaural spectral (pinna) cues present in broadband noise bursts. Single-unit response patterns differ according to binaural interactions, strength of monaural excitatory input from each ear, and Azimuth sensitivity to monaural stimulation. The latter characteristic has been used as a gauge of neural sensitivity to monaural spectral directional cues. Azimuth sensitivity may depend predominantly on binaural disparity cues, exclusively on monaural spectral cues, or on both. The primary goal of this study was to determine whether each cortical response pattern corresponds to a similar pattern in the medial geniculate body (MGB) or whether some patterns are unique to the cortex. Single-unit responses were recorded from the ventral nucleus (Vn) and lateral part of the posterior group of thalamic nuclei (Po), tonotopic subdivisions of the MGB. Responses to free-field presentation of noise bursts that varied in Azimuth and sound pressure level were obtained using methods identical to those used previously in field AI. Many units were Azimuth sensitive, i.e., they responded well at some Azimuths, and poorly, if at all, at others. These were studied further by obtaining responses to monaural noise stimulation, approximated by reversible plugging of one ear. Monaural directional (MD) cells were sensitive to the Azimuth of monaural noise stimulation, whereas binaural directional (BD) cells were either insensitive to its Azimuth or monaurally unresponsive. Thus BD and MD cells show differential sensitivity to monaural spectral cues. Monaural Azimuth sensitivity could not be used to interpret the spectral sensitivity of predominantly binaural cells that exhibited strong binaural facilitation because they were either unresponsive or poorly responsive to monaural stimulation. The available evidence suggests that some such cells are sensitive to spectral cues. The results do not indicate the presence of any response types in AI that are not present in the MGB. Vn and Po contain similar classes of MD and BD cells. Because Po neurons project to the anterior auditory field, neurons in this cortical area also are likely to exhibit differential sensitivity to binaural disparity and monaural spectral cues. Comparison of these MGB data with a published report of cochlear nucleus (CN) single-unit Azimuth tuning shows that MGB sensitivity to spectral cues is considerably stronger than CN sensitivity.

  • Effects of ear plugging on single-unit Azimuth sensitivity in cat primary auditory cortex. II. Azimuth tuning dependent upon binaural stimulation.
    Journal of neurophysiology, 1994
    Co-Authors: Frank K. Samson, Janine C. Clarey, Pascal Barone, Thomas J. Imig
    Abstract:

    1. Single-unit recordings were carried out in primary auditory cortex (AI) of barbiturate-anesthetized cats. Observations were based on a sample of 131 high-best-frequency (> 5 kHz), Azimuth-sensitive neurons. These were identified by their responses to a set of noise bursts, presented in the free field, that varied in Azimuth and sound-pressure level (SPL). Each Azimuth-sensitive neuron responded well to some levels at certain Azimuths, but did not respond well to any level at other Azimuths. 2. Unilateral ear plugging was used to infer each neuron's response to monaural stimulation. Ear plugs, produced by injecting a plastic ear mold compound into the external ear, attenuated sound reaching the tympanic membrane by 25-70 dB. The Azimuth tuning of a large proportion of the sample (62/131), referred to as binaural directional (BD), was completely dependent upon binaural stimulation because with one ear plugged, these cells were insensitive to Azimuth (either responded well at all Azimuths or failed to respond at any Azimuth) or in a few cases exhibited striking changes in location of Azimuth function peaks. This report describes patterns of monaural responses and binaural interactions exhibited by BD neurons and relates them to each cell's Azimuth and level tuning. The response of BD cells to ear plugging is consistent with the hypothesis that they derive Azimuth tuning from interaural level differences present in noise bursts. Another component of the sample consisted of monaural directional (27/131) cells that derived Azimuth tuning in part or entirely from monaural spectral cues. Cells in the remaining portion of the sample (42/131) responded too unreliably to permit specific conclusions. 3. Binaural interactions were inferred by statistical comparison of a cell's responses to monaural (unilateral plug) and binaural (no plug) stimulation. A larger binaural response than either monaural response was taken as evidence for binaural facilitation. A smaller binaural than monaural response was taken as evidence for binaural inhibition. Binaural facilitation was exhibited by 65% (40/62) of the BD sample (facilitatory cells). Many of these exhibited mixed interactions, i.e., binaural facilitation occurred in response to some Azimuth-level combinations, and binaural inhibition to others. Binaural inhibition in the absence of binaural facilitation occurred in 35% (22/62) of the BD sample, a majority of which were EI cells, so called because they received excitatory (E) input from one ear (excitatory ear) and inhibitory (I) input from the other (inhibitory ear). One cell that exhibited binaural inhibition received excitatory input from each ear.(ABSTRACT TRUNCATED AT 400 WORDS)

  • Effects of ear plugging on single-unit Azimuth sensitivity in cat primary auditory cortex. I. Evidence for monaural directional cues.
    Journal of neurophysiology, 1993
    Co-Authors: Frank K. Samson, Janine C. Clarey, Pascal Barone, Thomas J. Imig
    Abstract:

    1. Single-unit recordings were carried out in primary auditory cortex (AI) of barbiturate-anesthetized cats. Neurons, sensitive to sound direction in the horizontal plane (Azimuth), were identified by their responses to noise bursts, presented in the free field, that varied in Azimuth and sound pressure level (SPL). SPLs typically varied between 0 and 80 dB and were presented at each Azimuth that was tested. Each Azimuth-sensitive neuron responded well to some SPLs at certain Azimuths and did not respond well to any SPL at other Azimuths. This report describes AI neurons that were sensitive to the Azimuth of monaurally presented noise bursts. 2. Unilateral ear plugging was used to test each Azimuth-sensitive neuron's response to monaural stimulation. Ear plugs, produced by injecting a plastic ear mold compound into the concha and ear canal, attenuated sound reaching the tympanic membrane by 25-70 dB. Binaural interactions were inferred by comparing responses obtained under binaural (no plug) and monaural (ear plug) conditions. 3. Of the total sample of 131 Azimuth-sensitive cells whose responses to ear plugging were studied, 27 were sensitive to the Azimuth of monaurally presented noise bursts. We refer to these as monaural directional (MD) cells, and this report describes their properties. The remainder of the sample consisted of cells that either required binaural stimulation for Azimuth sensitivity (63/131), because they were insensitive to Azimuth under unilateral ear plug conditions or responded too unreliably to permit detailed conclusions regarding the effect of ear plugging (41/131). 4. Most (25/27) MD cells received either monaural input (MD-E0) or binaural excitatory/inhibitory input (MD-EI), as inferred from ear plugging. Two MD cells showed other characteristics. The contralateral ear was excitatory for 25/27 MD cells. 5. MD-E0 cells (22%, 6/27) were monaural. They were unaffected by unilateral ear plugging, showing that they received excitatory input from one ear, and that stimulation of the other ear was without apparent effect. On the other hand, some monaural cells in AI were insensitive to the Azimuth of noise bursts, showing that sensitivity to monaural directional cues is not a property of all monaural cells in AI. 6. MD-EI cells (70%, 19/27) exhibited an increase in responsiveness on the side of the plugged ear, showing that they received excitatory drive from one ear and inhibitory drive from the other. MD-EI cells remained Azimuth sensitive with the inhibitory ear plugged, showing that they were sensitive to monaural directional cues at the excitatory ear.(ABSTRACT TRUNCATED AT 400 WORDS)