posterThis poster describes how the connections within the central vocal pathways of African clawed frogs are responsible for coordinating distinct part of their calls

Barnes, Jessica C.

Yamaguchi, Ayako

English

The University of Utah: J. Willard Marriott Digital Library

ConclusionsThe biphasic phases of male X. laevis  vocalizations appear to be activated by the “initiator” neurons in DTAM.  Once thevocal phase is activated, fast trill rhythms seem to be generated by fast trill neurons in DTAM that receiveinput from both the n.IX-X and the ipsilateral DTAM.  The slow trill rhythms are likely to be generated by inter-neurons in n.IX-X that interact with the contralateral n.IX-X.  Phylogenetically, biphasic vocalizations are a more “derived”trait within the genus Xenopus , and many other species produce monophasic calls that resemble slow trills of X. laevis.Thus, understanding how neural circuits accommodate two vocal rhythms may provide us with an insight into the neuralmechanisms underlying the acquisition of new behaviors overevolutionary time.       .N.IX-XFictive vocalizations (top trace, below) can be elicited from an isolated brainstem (left) in vitro when serotoninis applied.  slow fast  Fast trill rhythms are likely to be generated by inDTAMAyako Yamaguchi and Jessica C. BarnesBiology Department, University of Utah, Salt Lake City, UT  Funding: NSF 1146501, Startup funds from the University of Utah  Distinct Neural Control of Vocal Phases in Frog Calls   584.07IntroductionThe behavior of animals is comprised of a variety of motions.  How are the motions underlying a functional behavior generated by the nervous system?  We used the vocalizations of African clawed frogs (Xenopus laevis) to address this question.  During the breeding season, a male Xenopus generates advertisement calls that consist of alternating fast and slow trill phases.  Fast and slow vocal trill phases contain a series of clicks repeated at 70 and 30 Hz, respectively.  Previously, using a fictive preparation in vitro, we discovered that the advertisement call is generated by the central pattern generator (CPG) in the brainstem.  The vocal CPG consists of a pair of premotor nuclei (DTAM) and a pair of laryngeal motor nuclei (n.IX-X) that are each interconnected. In this study, we examined how these nuclei contribute differently to the generation of fast and slow trill rhythms.  soundN.IX-XDTAM(premotor nucleus)n.IX-X(laryngeal motor nucleus)N.IX-X(laryngeal nerve)Xenopus advertisement calls consist of repetitive clicks that alternate between fast (70Hz) and slow (30Hz) rates (top trace, sound).  The temporal organizations of the callare dictated entirely by motor nerve activity (bottom trace, N.IX-X).  Motor command, in turn, is generated by the central pattern generator in the brainstem that consists of the dorsal tegmental area of medulla (DTAM, premotor nucleus, shown in red) and laryngeal motor nucleus (n.IX-X, shown in green).  The Advertisement Call of Xenopus laevis The Central Pattern Generator (CPG) DTAMfast slowThe central pattern generator that generates vocalizations consist of a pair of dorsal tegmental area of medulla(DTAM, premotor nucleus) and a pair of laryngeal motor nuclei (n.IX-X).  There are extensive reciprocal connections, including bilateral, descending, and ascending projections, among the DTAMs and n.IX-Xs as shown in the figure below (left).   to muscle??LMGMIX-XIX-XIX-XIX-XIX-XiDTAMDTAMiIX-XLMGMDTAMcIX-X DTAMcIX-XL?DTAMiIX-XIX-XcDTAMIX-XcDTAM IX-XiDTAM?IX-XiDTAM IX-XiDTAMto muscleDTAM DTAMn.IX-X n.IX-XLM: laryngeal motoneurons, GM: general visceral motoneurons, IX-XIX-X: n.IX-X projecting n.IX-X neuron, IX-XiDTAM: ipsilateral DTAM rojecting n.IX-X neuron,IX-XcDTAM: contralateral DTAM projecting n.IX-X neuron,  DTAMiIX-X: ipsilateral n.IX-X projecting DTAM neuron, DTAMcDTAM: contralateral n.IX-X projecting DTAM neuron. N.IX-XN.IX-Xafter transectionDTAMn.IX-Xbefore transectionThe connections between DTAM and n.IX-X are critical for the activation of both fast and slow trills  The application of serotonin to isolated brains that were bilaterally transected between DTAM-n.IX-X never   Hemi brainstem is sufficient to generate both fastand slow trillsleftrightleftrightleft N.IX-Xright N.IX-Xleft N.IX-Xright N.IX-XleftrightleftrightWhen the connections between left and right DTAMs and left and right n.IX-X are transected, each hemi brainstem  generated both fast and slow trills, although the rhythms generated by each half are autonomous, as evident in the  low cross correlation coefficient between left and right nerve traces during both fast and slow trills. ControlTransection1.  Unilateral transection btw DTAM and n.IX-X deteriorates fast trills, but not slow trills.  DTAMn.IX-XDTAMn.IX-XDTAMn.IX-X100ms1uVDTAMn.IX-X100ms1uV0.5uV5ms1uV10msLag Period (ms)-10 -8 -6 -4 -2 0 2 4 6 8 10Lag Period (ms)-10 -8 -6 -4 -2 0 2 4 6 8 10-0.400.40.82uV5ms1uV10ms100ms1uVleft N.IX-Xright N.IX-Xleft N.IX-Xright N.IX-XFast trill Slow trill-0.400.40.8tneiciff eoC noit al err oC ssorCleftrightleftrightleftrightleftrightWhen the connections between DTAMs and n.IX-X are transected unilaterally, fast trill became deformed drastically while slow trill remained unchanged.  The compound action potential (CAPs) recorded from both right and left nerve became significantly reduced in amplitude, and their timing became desynchronized.  CAPs during slow trill, in contrast, were similar to those recorded from intact brains.  Cross-correlation coefficientLag Period (ms)-10 -8 -6 -4 -2 0 2 4 6 8 100.400.40.8-10 -8 -6 -4 -2 0 2 4 6 8 10Fast trill Slow trillcontroltransected2.  Transection between DTAMs deteriorates the bilateral synchrony of fast trills, but not slow trills. Unilateral transection reduces the amplitude of compound action potentials during the fast trills, but not during the slow trills.Unilateral transection reduces the bilateral synchrony of compound action potentials during the fast trills, but not during the slow trills.controltransectedcontroltransectedDTAMn.IX-XDTAMn.IX-X1uV500ms1uV500ms2uV4ms2uV4ms0.5uV10ms0.5uV10msFast trill Slow trillLag Period (ms)-10 -8 -6 -4 -2 0 2 4 6 8 10-0.400.40.8tneiciff eoC noit al err oC ssorC-10 -8 -6 -4 -2 0 2 4 6 8 10resulted in fast or slow trills.ControlTransectionFast trill Slow trillControlTransectionIsolating the left and right DTAMs reduces the bilateral synchrony of compound action potentials during the fast trills, but not during the slow trills.Question: How are two distinct vocal rhythms  initiated and generated by the central pattern generator? Slow trill rhythms are likely to be generated by n.IX-XTransection between n.IX-X deteriorates the bilateral synchrony between right and left motor nerves during the slow trills, but not during the fast trills. DTAMn.IX-XDTAMn.IX-X1uV200ms1uV200msleft N.IX-Xright N.IX-Xleft N.IX-Xright N.IX-XleftrightleftrightleftrightleftrightLag Period (ms)-10 -8 -6 -4 -2 0 2 4 6 8 10 -10 -8 -6 -4 -2 0 2 4 6 8 10controltransected-0.400.40.8tneiciff eoC noit al err oC ssorCFast trill Slow trill090270090180270Circular Phase Distributioncontroltransected090180270901800270Circular Phase DistributionGiven the selective effect of the transection on the slow trill synchrony, it is likely that the right and left n.IX-X function together to generate slow trill rhythms.Selective deterioration of fast trills in these experiments suggests that left and right DTAM function together to generate fast trill rhythms and drive the motoneurons.  fast slow500msec500 ms20 mV500 ms20 mVWhole cellNerve200 ms20 mVVocal phase initiators: Neurons that could initiate fast and slow trills are found in DTAMPre-fast trill neuronPost-fast trill neuronPre-fast trill neurons spike before the onset of the fast trill is detected on the laryngealnerve.  As the fast trill progresses, the neuron stops spiking.  Post-fast trill neurons spike after the fast trill, even in the absence of slow trills.  Thespikes of the neuron has little to do with the timing of the slow trills.  These neurons may initiate both vocal phases, and may explain why no vocalizations can be activated in the absence of functional DTAMs.  Vocal rhythm generators: Neurons likely to be the fast trill rhythm generators are found in DTAMFast trill neuronFast trill neurons spike action potentials selectively during the fast trill, and each spike precede the compoundaction potential by ~2msec.  The fast trill neurons (FTNs) likely act as rhythm generators for the fast trill.  Our previous results suggest that FTNs do not generate endogenous rhythmsautonomously, but require ascending feedback from the n.IX-X.  As for the slow trill rhythm generator neurons, we are currently in search for suchneurons in the n.IX-X.      

Distinct neural control of vocal phases in frog calls

https://collections.lib.utah.edu/dl_files/c2/0e/c20e51c2f2a3dd52a2b3046725f936638fe03cf9.pdf

Distinct neural control of vocal phases in frog calls

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