The Journal of Neuroscience, February 1, 2002, 22(3):946-958
The Role of Auditory Experience in the Formation of Neural
Circuits Underlying Vocal Learning in Zebra Finches
Soumya
Iyengar and
Sarah W.
Bottjer
Department of Biology, University of Southern California, Los
Angeles, California 90089-2520
The initial establishment of topographic mapping within developing
neural circuits is thought to be shaped by innate mechanisms and is
primarily independent of experience. Additional refinement within
topographic maps leads to precise matching between presynaptic and
postsynaptic neurons and is thought to depend on experiential factors
during specific sensitive periods in the animal's development. In male
zebra finches, axonal projections of the cortical lateral magnocellular
nucleus of the anterior neostriatum (lMAN) are critically important for vocal learning. Overall patterns of topographic organization in the majority of these circuits are adult-like throughout the sensitive period for vocal learning and remain stable
despite large-scale functional and morphological changes. However,
topographic organization within the projection from the core subregion
of lMAN (lMANcore) to the motor cortical robust nucleus of
the archistriatum (RA) is lacking at the onset of song development and emerges during the early stages of vocal learning. To
study the effects of song-related experience on patterns of axonal
connectivity within different song-control circuits, we disrupted song
learning by deafening juvenile zebra finches or exposing them to loud
white noise throughout the sensitive period for song learning.
Depriving juvenile birds of normal auditory experience delayed the
emergence of topographic specificity within the
lMANcore
RA circuit relative to age-matched controls,
whereas topographic organization within all other projections to and
from lMAN was not affected. The projection from lMANcore to
RA therefore provides an unusual example of experience-dependent
modification of large-scale patterns of brain circuitry, in the sense
that auditory deprivation influences the development of overall
topographic organization in this pathway.
Key words:
topographic organization; sensory experience; sensitive
periods; zebra finch; songbird; vocal learning.
Copyright © 2002 Society for Neuroscience 0270-6474/02/223946-13$05.00/0
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