Vocal neurons encode evolution of frog calls

Clawed frog (Xenopus) species are distinguished by the vocalizations that males use to attract females. To investigate what contributes to these differences, Erik Zornik and colleagues compared the activity of premotor vocal neurons in dissected brains from two species, X. laevis and X. petersii, which diverged from a common ancestor about 8.5 million years ago.

Applying the neurotransmitter serotonin to the premotor parabrachial area of the isolated brains to produce fictive calls, the researchers identified two groups of cells in these closely-related species that are active during calls. They found that while the properties of Early Vocal Neurons were similar between the species, those of Fast Trill Neurons were unique and corresponded to the calls characteristic of each species. The parabrachial area is involved in the control of breathing across vertebrates, suggesting that these ancient circuits may have enabled the evolution of vocal patterns.