Neuronal activity and anatomical connectivity of the mammalian motor nucleus of laryngeal control in the context of vocalization and auditory feedback control
Final Report Abstract
Echolocating Greater Horseshoe Bats adjust their call frequency depending on their auditory feedback provided by the returning echo in a phenomenon called Dopplershift compensation. Changes in call frequency are modulated by a single laryngeal muscle, the cricothyroid muscle, which is innervated by the anterior part of the nucleus ambiguus (NA). In the first project, we showed that injections of GABA agonists and antagonists affected NA neurons whose activity is directly correlated with call frequency. Injections of glutamatergic drugs revealed no effects on the activity of frequency-correlated neurons in the anterior part of NA. These results are consistent with the idea of inhibitory premotor input. Frequency-correlated neurons in the anterior NA whose activity was inhibited during call emission might serve as the inhibitory source to decrease intrinsic spontaneous activity of NA motor neurons. These data show for the first time that the control of a motor neuron pool, involved in vocalization, is controlled by decreasing spontaneous activity of motor neurons through inhibitory input rather than by excitatory input. To further understand the control of call frequency in echolocating bats, we aimed to characterize the biomechanical properties of the larynx to isolate vocal features which arise independently from neuronal input. Using an isolated larynx preparation, we demonstrated that it could generate most spectral features of natural horseshoe bat vocalizations without any input from the brain. Small changes in laryngeal air flow produced non-linear effects on sound production, whereas cricothyroid muscle stimulation produced highly linear frequency changes. The combination of both nonlinear and linear operational modes allowed the larynx to produce calls covering the entire range of frequencies used for echolocation and communication. In addition to elucidating the mechanisms controlling mammalian vocalizations, these results may potentially be applied in to advancing sonar applications. While bats with frequency-modulated calls (FM-bats) show a change in their call structure when external noise is present, bats with constant-frequency calls (CF-bats) are commonly assumed to lack a specific jamming avoidance response because of their extremely narrow spectral composition. Here, we show the first evidence to suggest that CF-bats also display jamming avoidance behavior. The inclusion of CF-bats in further studies on jamming avoidance may further improve the understanding of how this response is controlled by the brain.
Publications
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(2008) Call frequency control by neurons in the vocal motor nucleus in echolocating horseshoe bats. Program No. 796.13. 2008 Abstract Viewer/Itinerary Planner. Washington, DC: Society for Neuroscience
Hage SR, Kobayasi K, Metzner W
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(2008) How laryngeal dynamics affect call frequency in an echolocating bat. Program No. 796.14. 2008 Abstract Viewer/Itinerary Planner. Washington, DC: Society for Neuroscience
Kobayasi K, Hage SR, Berquist S, Metzner W
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(2008) Vocal motor control in horseshoe bats – a bottom-up approach. J Acoust Soc Am 123: 3205
Kobayasi K, Hage SR, Ma, J & Metzner W
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(2009) Call frequency control by neurons in the vocal motor nucleus in Greater Horseshoe Bats. Proceedings of the 8th Meeting of the German Neuroscience Society. Göttingen, Germany. Itinerary Planner: T18-12C
Hage SR, Kobayasi K, Metzner W
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(2009) Localization of the central pattern generator for vocalization. In: Brudzynski SM (ed.) Handbook of mammalian vocalization. Academic Press, Oxford: 339-349
Hage SR
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(2009) Neuronal networks involved in the generation of vocalization. In: Brudzynski SM (ed.) Handbook of mammalian vocalization. Academic Press, Oxford: 329-338
Hage SR
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(2009) “Jamming avoidance” in bats with narrow-band echolocation pulses. 2009 Abstract Viewer/Itinerary Planner. Chicago, Society for Neuroscience
Hage SR, Jiang T, Berquist S, Metzner W
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(2009) “Jamming avoidance” in bats with narrow-band echolocation pulses. 5th Animal Sonar Symposium, Kyoto, Japan
Hage SR, Jiang T, Berquist S, Metzner W
