The Experts below are selected from a list of 186 Experts worldwide ranked by ideXlab platform
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.
John J. Guinan - One of the best experts on this subject based on the ideXlab platform.
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Motoneuron axon distribution in the cat Stapedius muscle.
Hearing research, 1999Co-Authors: S R Wiener-vacher, John J. Guinan, J B Kobler, B E NorrisAbstract:Stapedius-motoneuron cell bodies in the brainstem are spatially organized according to their acoustic response laterality, as demonstrated by intracellular labeling of physiologically identified motoneurons [Vacher et al., 1989. J. Comp. Neurol. 289, 401-415]. To determine whether a similar functional spatial segregation is present in the muscle, we traced physiologically identified, labeled axons into the Stapedius muscle. Ten labeled axons were visible in the facial nerve and five could be traced to endplates within the muscle. These five axons had 39 observed branches (others may have been missed). This indicates an average innervation ratio (> or = 7.8) which is much higher than that obtained from previous estimates of the numbers of Stapedius motoneurons and muscle fibers in the cat. One well-labeled Stapedius motor axon innervated only a single muscle fiber. In contrast, two labeled axons had over 10 endings and innervated muscle fibers spread over wide areas in the muscle. Two of the axons branched and coursed through two primary Stapedius fascicles, indicating that the muscle zones innervated by different primary fascicles are not functionally segregated. In another series of experiments, retrograde tracers were deposited in individual primary nerve fascicles. In every case, labeled Stapedius-motoneuron cell bodies were found in each of the physiologically identified Stapedius-motoneuron regions in the brainstem. These observations suggest there is little, if any, functional spatial segregation based on separate muscle compartments in the Stapedius muscle, despite there being functional spatial segregation in the Stapedius-motoneuron pool centrally.
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Effects of Stapedius-muscle contractions on the masking of auditory-nerve responses
The Journal of the Acoustical Society of America, 1997Co-Authors: Xiao Dong Pang, John J. GuinanAbstract:There has been little exploration of the mechanisms by which Stapedius muscle contractions reduce the masking of responses to high-frequency sounds by low-frequency sounds. To fill this gap in knowledge, controlled Stapedius contractions were elicited with direct shocks in anesthetized cats, and measurements were made of the effects of these contractions on the masking of single auditory-nerve fibers and on the attenuation of middle-ear transmission. The results show that the Stapedius-induced reductions of masking can be much larger than the attenuations of low-frequency sound. With a 300-Hz band of masking noise centered at 500 Hz, and signal tones at 6 or 8 kHz, unmasking effects over 40 dB were observed for sounds 100 dB SPL or less. The data suggest that much larger unmasking might occur. The observed unmasking can be explained completely by a linear Stapedius-induced attenuation of sound transmission through the middle ear and a nonlinear growth rate of masking for auditory-nerve fibers. No central effects are required. It is argued that the reduction of the upward spread of masking is probably one of the most important functions of the Stapedius muscle.
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Acoustic reflex frequency selectivity in single Stapedius motoneurons of the cat
Journal of neurophysiology, 1992Co-Authors: James B. Kobler, John J. Guinan, Sylvette R. Vacher, Barbara E. NorrisAbstract:1. The sound frequency selectivities of single Stapedius motoneurons were investigated in ketamine anesthetized and in decerebrate cats by recording from axons in the small nerve fascicles entering the Stapedius muscle. 2. Stapedius motoneuron tuning curves (TCs) were very broad, similar to the tuning of the overall acoustic reflexes as determined by electromyographic recordings. The lowest thresholds were usually for sound frequencies between 1 and 2 kHz, although many TCs also had a second sensitive region in the 6- to 12-kHz range. The broad tuning of Stapedius motoneurons implies that inputs derived from different cochlear frequency regions (which are narrowly tuned) must converge at a point central to the Stapedius motoneuron outputs, possibly at the motoneuron somata. 3. There were only small differences in tuning among the four previously described groups of Stapedius motoneurons categorized by sensitivity to ipsilateral and contralateral sound. The gradation in high-frequency versus low-frequency sensitivity across motoneurons suggests there are not distinct subgroups of Stapedius motoneurons, based on their TCs. 4. The thresholds and shapes of Stapedius motoneuron TCs support the hypothesis that the Stapedius acoustic reflex is triggered by summed activity of low-spontaneous-rate auditory nerve fibers with both low and high characteristic frequencies (CFs). Excitation of high-CF auditory nerve fibers by sound in their TC “tails” is probably an important factor in eliciting the reflex. 5. In general, the most sensitive frequency for Stapedius motoneurons is higher than the frequency at which Stapedius contractions produce the greatest attenuation of middle ear transmission. We argue that this is true because the main function of the Stapedius acoustic reflex is to reduce the masking of responses to high-frequency sounds produced by low-frequency sounds.
Silvarosa Grassi - 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.
Barbara E. Norris - One of the best experts on this subject based on the ideXlab platform.
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Acoustic reflex frequency selectivity in single Stapedius motoneurons of the cat
Journal of neurophysiology, 1992Co-Authors: James B. Kobler, John J. Guinan, Sylvette R. Vacher, Barbara E. NorrisAbstract:1. The sound frequency selectivities of single Stapedius motoneurons were investigated in ketamine anesthetized and in decerebrate cats by recording from axons in the small nerve fascicles entering the Stapedius muscle. 2. Stapedius motoneuron tuning curves (TCs) were very broad, similar to the tuning of the overall acoustic reflexes as determined by electromyographic recordings. The lowest thresholds were usually for sound frequencies between 1 and 2 kHz, although many TCs also had a second sensitive region in the 6- to 12-kHz range. The broad tuning of Stapedius motoneurons implies that inputs derived from different cochlear frequency regions (which are narrowly tuned) must converge at a point central to the Stapedius motoneuron outputs, possibly at the motoneuron somata. 3. There were only small differences in tuning among the four previously described groups of Stapedius motoneurons categorized by sensitivity to ipsilateral and contralateral sound. The gradation in high-frequency versus low-frequency sensitivity across motoneurons suggests there are not distinct subgroups of Stapedius motoneurons, based on their TCs. 4. The thresholds and shapes of Stapedius motoneuron TCs support the hypothesis that the Stapedius acoustic reflex is triggered by summed activity of low-spontaneous-rate auditory nerve fibers with both low and high characteristic frequencies (CFs). Excitation of high-CF auditory nerve fibers by sound in their TC “tails” is probably an important factor in eliciting the reflex. 5. In general, the most sensitive frequency for Stapedius motoneurons is higher than the frequency at which Stapedius contractions produce the greatest attenuation of middle ear transmission. We argue that this is true because the main function of the Stapedius acoustic reflex is to reduce the masking of responses to high-frequency sounds produced by low-frequency sounds.
Domenico Bambagioni - 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.
