The Journal of Neuroscience, February 15, 2000, 20(4):1559-1567
Generating Sexually Differentiated Vocal Patterns: Laryngeal
Nerve and EMG Recordings from Vocalizing Male and Female African Clawed
Frogs (Xenopus laevis)
Ayako
Yamaguchi and
Darcy B.
Kelley
Department of Biological Sciences, Columbia University, New York,
New York 10027
Male and female African clawed frogs (Xenopus
laevis) produce sexually dimorphic vocalizations; for males
these include advertisement, amplectant, and growling calls, whereas
female calls include ticking. Previous studies have shown that the
vocal organ, the larynx, of the sexes differs in physiological
properties that parallel vocal differences. However, it was not clear
whether these characteristics are sufficient to explain sex differences
in vocal behavior. To examine the contribution of the CNS to
generating vocal patterns, we developed a preparation in which both
laryngeal nerve activity and electromyograms can be recorded from
awake, vocalizing frogs. Recordings reveal that the CNS of the two
sexes produces patterned activity that closely matches each
vocalization whereas the larynx faithfully translates nerve activity
into sound. Thus, the CNS is the source of sexually differentiated
vocalizations in Xenopus laevis. Furthermore, detailed
analyses of compound action potentials recorded from the nerve lead us
to hypothesize that neuronal activity underlying different male call
types is distinct; some calls are likely to be generated by synchronous
firing of motoneuron populations of either constant size or
progressively larger sizes, whereas others are generated by
asynchronous activity of motoneurons, a pattern shared with vocal
production in females. We suggest that these distinct neuronal activity
patterns in males may be subserved by two populations of motor units in
males that can be distinguished by the strength of the neuromuscular synapse.
Key words:
vocalizations; nerve recordings; electromyograms; Xenopus laevis; sex differences; compound action
potentials
Copyright © 2000 Society for Neuroscience 0270-6474/00/2041559-09$05.00/0
Previous Article | Next Article
