![]() ![]() These temperature effects have been shown to be due to a slowing of processes at the level of the CPG rather than at the level of the motoneurons or muscles themselves (e.g., Bauer and von Helversen 1987). Rhythmic motor patterns of ectotherms typically operate at reduced rates at lower temperatures due to a slowing of their underlying CPG. In this study, we attempted to localize the CPG responsible for generating vocal rhythms in African clawed frogs ( Xenopus laevis) by exploiting the temperature dependence of a vocal pattern generator. Although the identification of interneurons that form the CPG are the critical first steps toward understanding cellular and synaptic bases of rhythm generation, localizing CPG is often difficult because of the complex structure of the CNS (reviewed by Marder and Calabrese 1996). Changes in these cellular and synaptic properties within the CPG network can modify resulting motor rhythms (reviewed by Marder and Bucher 2007 Simmers et al. Motor rhythms generated by the CPG depend both on the intrinsic membrane properties of constituent neurons and their synaptic interactions (reviewed by Getting 1989 Marder and Bucher 2007 Marder and Calabrese 1996 Metzner 1999 Ramirez and Viemari 2005 Roberts et al. Twitch leecher 404 not found generator#In many systems, these motor patterns are controlled by a central pattern generator (CPG), a network of neurons that drives motoneurons to spike rhythmically in the absence of sensory feedback. Motor patterns expressed by animals are often rhythmic. Thus we conclude that DTAM is a source of biphasic vocal rhythms. We found that bilateral cooling of DTAM reduced both fast and slow trill rates. We focused on the dorsal tegmental area of the medulla (DTAM), a brain stem nucleus that is essential for vocal production. We next took advantage of the temperature sensitivity of the vocal CPG in vitro to localize the source of the vocal rhythms. Temperature did not limit the contractile properties of laryngeal muscles within the frequency range of vocalizations. In vitro a similar linear relation between temperature and compound action potential frequency in the laryngeal nerve was found when fictive advertisement calls were evoked in the isolated brain. ![]() In vivo the rates of fast and slow trills increased linearly with an increase in temperature. We found that the trill rate of these advertisement calls is sensitive to temperature and that this rate modification of the vocal rhythms originates in the central pattern generators. laevis is a complex biphasic motor rhythm consisting of fast and slow trills (a train of clicks). Vocalizations of Xenopus laevis are generated by central pattern generators (CPGs). ![]()
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