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Erik Borg - One of the best experts on this subject based on the ideXlab platform.
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assessment of auditory brainstem function in lead exposed children using Stapedius Muscle reflexes
Journal of the Neurological Sciences, 2011Co-Authors: S. A. Counter, Leo H Buchanan, Fernando Ortega, Jeannette Van Der Velde, Erik BorgAbstract:Abstract The purpose of this study was to investigate the neurological integrity and physiological status of the auditory brainstem tracts and nuclei in children with chronic lead (Pb) exposure using non-invasive acoustic Stapedius reflex (ASR) measurements of afferent and efferent-neuromuscular auditory function. Following audiological examinations, uncrossed (ipsilateral) and crossed (contralateral) brainstem ASR responses were evoked by pure tone (500, 1000, and 2000 Hz), and broadband noise (bandwidth: 125–4000 Hz) stimulus activators. The ASR threshold (ASRT), amplitude growth, and decay/fatigue were measured by conventional clinical middle ear immittance methods in a group of Andean children (age range: 2–18 years) with a history of chronic environmental Pb exposure from occupational Pb glazing. Blood lead (PbB) levels of the study group (n = 117) ranged from 4.0 to 83.7 μg/dL with a mean PbB level of 33.5 μg/dL (SD: 23.6; median: 33.0: CDC III Classification). The PbB distribution data indicated that 77.8% (n = 91) of the children had PbB levels greater than the CDC action line of 10 μg/dL. Repeatable, normal ASRTs were elicited for ipsilateral (mean: ≤ 90 dB HL) and contralateral (mean: ≤ 97 dB HL) stimulation for each acoustic activator. Spearman Rho correlation analysis indicated no significant association between PbB level and ipsilateral or contralateral ASRT for any of the stimulus activators. The ASR amplitude growth results showed typical growth functions with no Pb-associated aberrations. No statistical association was found between ASR decay/adaptation (ASRD) and PbB level for any of the stimulus activators. The results of Stapedius Muscle reflex testing using several stimulus activators showed no significant relationship between PbB level and the physiological integrity of the auditory brainstem mediated ASR responses in children with chronic Pb exposure and elevated PbB levels.
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Physiological activation of the Stapedius Muscle in Gallus gallus.
Acta Oto-laryngologica, 2009Co-Authors: S. A. Counter, Erik BorgAbstract:The function of the avian middle ear Muscle was investigated in the chicken, Gallus gallus (domesticus). The avian species offers excellent conditions for study of middle ear Muscle function since it possesses a single middle ear Muscle, the Stapedius, which is located extracranially. Electromyograms (EMG), measurements of impedance change, and volume change in the middle ear cavity were used to assess the Muscle's activity. The results showed that the middle ear Muscle of Gallus does not exhibit an acoustic reflex. However, the Stapedius is regularly activated during the animal's own vocalization. Measurements of the EMG and volume change showed the stapedial activity to increase systematically with increases in the vocal sound level. The use of volume change as a measure of Stapedius function was found to be highly suitable in the present experiments in that it allows for measurements of the magnitude of the Stapedius contraction without altering the intact physiological state of the middle ear, and is ...
Jozef J. Zwislocki - One of the best experts on this subject based on the ideXlab platform.
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A look at neural integration in the human auditory system through the Stapedius Muscle reflex.
Proceedings of the National Academy of Sciences of the United States of America, 2003Co-Authors: Jozef J. ZwislockiAbstract:Ipsilateral and contralateral Stapedius Muscle contractions were studied as functions of the sound pressure level (SPL) and duration of 2-kHz tone bursts. The study complemented a preceding study in which temporal summation of Stapedius Muscle contractions produced by pairs of short tone bursts was determined and analyzed. The Muscle contractions were determined indirectly by measuring changes in the acoustic impedance they produced at the tympanic membrane. The data for the Stapedius Muscle contraction as a function of tone-burst duration were derived from another study and analyzed in part with the help of the SPL functions obtained in the present study. According to the experimental results, the Stapedius Muscle contraction produced by contralateral stimulation follows a compressive power function paralleling both the cochlear output and loudness functions. The ipsilateral contraction follows an expansive power function. Mathematical analysis showed that the Muscle tension due to contralateral stimulation increases with tone duration approximately according to the characteristic of a linear integrator having an exponentially decaying memory with a time constant that increases with SPL from ≈200 to 370 msec. The simple relationship appears to be possible because of mutual cancellation of neural-processing characteristics preceding and following the temporal integration.
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auditory system peripheral nonlinearity and central additivity as revealed in the human Stapedius Muscle reflex
Proceedings of the National Academy of Sciences of the United States of America, 2002Co-Authors: Jozef J. ZwislockiAbstract:Human Stapedius-Muscle contractions in response to 3-kHz, 20-msec tone bursts were determined indirectly by measuring the associated acoustic-impedance changes at the tympanic membrane with an acoustic bridge. The measurement was possible because the bridge practically eliminates the effect of the ear-canal air volume interposed between the tympanic membrane and the tip of the measuring tube. By using burst pairs, temporal additivity of the Muscle responses was demonstrated both when the stimulus bursts were presented contralaterally to the measured impedance changes and when the first burst was presented ipsilaterally. The summation time constant was on the order of 200 msec, much longer than the twitch time constant of the Muscle fibers. Therefore, the summation had to take place in a nucleus preceding the Stapedius Muscle. The magnitude of the Muscle response obeyed a compressive function paralleling the loudness function up to sound pressure levels of at least 120 dB.
G Serafini - One of the best experts on this subject based on the ideXlab platform.
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Acoustic structure of vocalization and Stapedius Muscle activity during vocal development in chickens (Gallus gallus).
Journal of comparative physiology. A Sensory neural and behavioral physiology, 1993Co-Authors: Silvarosa Grassi, Fabrizio Ottaviani, Domenico Bambagioni, G SerafiniAbstract:The link between Stapedius Muscle activity and acoustic structure of vocalization was analysed in cocks of age 20-30 to 90-100 days old. The results show that Stapedius Muscle activation depends on the acoustic structure of vocalization and changes during vocal development. This dependence was observed in spontaneous calls and in vocalizations elicited by stimulating the mesencephalic "calling area". In 30-day-old cocks Stapedius Muscle EMG response is never associated with vocalizations with an acoustic energy content which is always distributed at frequencies higher than 2000 Hz. The coupling between vocalization and Stapedius Muscle activity begins later, when birds produce vocalizations with acoustic energy shifted towards lower frequencies. Overall, Stapedius Muscle activity is related to a bird's production of high amplitude low frequencies. These results support the hypothesis that the primary role of the Stapedius Muscle during normal vocal development is to dampen the amplitude of low frequency energy that reaches the cochlea during vocalization.
S. A. Counter - One of the best experts on this subject based on the ideXlab platform.
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assessment of auditory brainstem function in lead exposed children using Stapedius Muscle reflexes
Journal of the Neurological Sciences, 2011Co-Authors: S. A. Counter, Leo H Buchanan, Fernando Ortega, Jeannette Van Der Velde, Erik BorgAbstract:Abstract The purpose of this study was to investigate the neurological integrity and physiological status of the auditory brainstem tracts and nuclei in children with chronic lead (Pb) exposure using non-invasive acoustic Stapedius reflex (ASR) measurements of afferent and efferent-neuromuscular auditory function. Following audiological examinations, uncrossed (ipsilateral) and crossed (contralateral) brainstem ASR responses were evoked by pure tone (500, 1000, and 2000 Hz), and broadband noise (bandwidth: 125–4000 Hz) stimulus activators. The ASR threshold (ASRT), amplitude growth, and decay/fatigue were measured by conventional clinical middle ear immittance methods in a group of Andean children (age range: 2–18 years) with a history of chronic environmental Pb exposure from occupational Pb glazing. Blood lead (PbB) levels of the study group (n = 117) ranged from 4.0 to 83.7 μg/dL with a mean PbB level of 33.5 μg/dL (SD: 23.6; median: 33.0: CDC III Classification). The PbB distribution data indicated that 77.8% (n = 91) of the children had PbB levels greater than the CDC action line of 10 μg/dL. Repeatable, normal ASRTs were elicited for ipsilateral (mean: ≤ 90 dB HL) and contralateral (mean: ≤ 97 dB HL) stimulation for each acoustic activator. Spearman Rho correlation analysis indicated no significant association between PbB level and ipsilateral or contralateral ASRT for any of the stimulus activators. The ASR amplitude growth results showed typical growth functions with no Pb-associated aberrations. No statistical association was found between ASR decay/adaptation (ASRD) and PbB level for any of the stimulus activators. The results of Stapedius Muscle reflex testing using several stimulus activators showed no significant relationship between PbB level and the physiological integrity of the auditory brainstem mediated ASR responses in children with chronic Pb exposure and elevated PbB levels.
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Physiological activation of the Stapedius Muscle in Gallus gallus.
Acta Oto-laryngologica, 2009Co-Authors: S. A. Counter, Erik BorgAbstract:The function of the avian middle ear Muscle was investigated in the chicken, Gallus gallus (domesticus). The avian species offers excellent conditions for study of middle ear Muscle function since it possesses a single middle ear Muscle, the Stapedius, which is located extracranially. Electromyograms (EMG), measurements of impedance change, and volume change in the middle ear cavity were used to assess the Muscle's activity. The results showed that the middle ear Muscle of Gallus does not exhibit an acoustic reflex. However, the Stapedius is regularly activated during the animal's own vocalization. Measurements of the EMG and volume change showed the stapedial activity to increase systematically with increases in the vocal sound level. The use of volume change as a measure of Stapedius function was found to be highly suitable in the present experiments in that it allows for measurements of the magnitude of the Stapedius contraction without altering the intact physiological state of the middle ear, and is ...
Randolf Riemann - One of the best experts on this subject based on the ideXlab platform.
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motoneurons of the Stapedius Muscle in the guinea pig middle ear afferent and efferent transmitters
Brain Research, 2008Co-Authors: Stefan Reuss, Sandy Albutmeh, Randolf RiemannAbstract:The objective of the present study was to identify efferent and afferent transmitters of motoneurons of the Stapedius Muscle of the middle ear in order to gain more insight into the neuronal regulation of the Muscle. To identify motoneurons, we injected the fluorescent neuronal tracer Fluorogold (FG) into the Muscle after preparation of the middle ear in adult guinea pigs. Upon terminal uptake and retrograde neuronal transport, we observed FG in neurons located medial and ventral to the nucleus of the facial nerve ipsilateral to the injection site. Immunohistochemical studies of these motoneurons showed that the majority contains calcitonin gene-related peptide. Our data further demonstrate close spatial relationships of motoneurons to structures immunoreactive to either serotonin, substance P or neuronal nitric oxide and reveal that these neurons are under neuropeptidergic and nitrergic influence.