Cross Fostering Experiments Suggest That Mice Songs Are Innate

Background

Vocal learning is a central functional constituent of human speech, and
recent studies showing that adult male mice emit ultrasonic sound sequences
characterized as “songs” have suggested that the ultrasonic
courtship sounds of mice provide a mammalian model of vocal learning.

Objectives

We tested whether mouse songs are learned, by examining the relative role of
rearing environment in a cross-fostering experiment.

Methods and Findings

We found that C57BL/6 and BALB/c males emit a clearly different pattern of
songs with different frequency and syllable compositions; C57BL/6 males
showed a higher peak frequency of syllables, shorter intervals between
syllables, and more upward frequency modulations with jumps, whereas BALB/c
males produced more “chevron” and “harmonics”
syllables. To establish the degree of environmental influences in mouse song
development, sons of these two strains were cross-fostered to another strain
of parents. Songs were recorded when these cross-fostered pups were fully
developed and their songs were compared with those of male mice reared by
the genetic parents. The cross-fostered animals sang songs with acoustic
characteristics – including syllable interval, peak frequency, and
modulation patterns – similar to those of their genetic parents. In addition
their song elements retained sequential characteristics similar to those of
their genetic parents’ songs.

Conclusion

These results do not support the hypothesis that mouse “song” is
learned; we found no evidence for vocal learning of any sort under the
conditions of this experiment. Our observation that the strain-specific
character of the song profile persisted even after changing the
developmental auditory environment suggests that the structure of these
courtship sound sequences is under strong genetic control. Thus, the
usefulness of mouse “song” as a model of mammalian vocal
learning is limited, but mouse song has the potential to be an indispensable
model to study genetic mechanisms for vocal patterning and behavioral
sequences.

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Cross Fostering Experiments Suggest That Mice Songs Are
Innate
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