Journal of Neuroscience, Vol 11, 2362-2371, Copyright © 1991 by Society for Neuroscience
Chronic testosterone treatment impairs vocal learning in male zebra finches during a restricted period of development
S Korsia and SW Bottjer
Department of Biological Sciences, University of Southern California, Los Angeles 90089-2520.
To study the effects of chronic exposure to testosterone on song behavior
development, we administered various amounts of testosterone to juvenile
male zebra finches during different periods of song acquisition. We report
that testosterone exposure during development profoundly impairs song
learning in juvenile males. The effects of the hormone do not seem to be
dose related but vary according to the period of life during which
testosterone is administered. Exposure to testosterone starting before day
40 and lasting until adulthood decreases the number of syllables in the
birds' repertoire and increases the number of phrases per bout of singing.
In addition to these changes in the "syntactical" features of song,
acoustic abnormalities are also present in the song syllables of males that
begin to receive testosterone during the first month of life.
Administration of testosterone during only the first 3 weeks of life
produces acoustic abnormalities but has no effect on repertoire size or
bout structure. Birds receiving the hormone between 20 and 40 d of age
develop both acoustic abnormalities and a reduced repertoire size, but
their song bouts contain a normal number of song phrases. Exposure to
testosterone starting on day 40 produce no behavioral abnormalities. These
results indicate that normal song development requires a period of low
levels of circulating testosterone and also provide support for the idea
that vocal learning entails a progressive sequence of events.
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