The Journal of Neuroscience, December 15, 2002, 22(24):10864-10870
Vocal Control Neuron Incorporation Decreases with Age in the
Adult Zebra Finch
Niangui
Wang,
Patrick
Hurley,
Carolyn
Pytte, and
John
R.
Kirn
Department of Biology, Wesleyan University, Middletown, Connecticut
06459
In adult male zebra finches, high vocal center (HVC) neurons
continuously die and are replaced. Many of these cells are projection neurons that form part of the efferent pathway controlling learned song
production. Although it is known that HVC receives new neurons well
into adulthood, it is unknown whether this occurs at a constant rate or
declines with adult age. We used [3H]thymidine to
label new HVC neurons in male zebra finches that were 3-36 months of
age. Birds were killed 4 months after 3H injections to
measure the long-term incorporation of new HVC neurons. HVC neurons
projecting to the robust nucleus of the archistriatum (HVC-RA) were
retrogradely labeled with Fluoro-Gold 4 d before death. We found a
dramatic age-related decline in the number of 3H-labeled
HVC-RA neurons present 4 months after cell birth dating. A similar
decline in new HVC neurons was found as soon as 1 month after their
formation. These results indicate that the production or early survival
of adult-formed neurons decreases with age. HVC volume and total neuron
number did not change with bird age, suggesting that the age-related
decrease in new neuron addition was balanced by increased survivorship
of neurons incorporated previously. Reliance of song structure on
auditory feedback also wanes with age. We propose that with aging,
fewer new cells are added as the numbers of functionally appropriate
cells increase, a process that may be linked to age-related increases
in motor program stability.
Key words:
adult neurogenesis; birdsong; aging; zebra finch; motor
learning; apoptosis
Copyright © 2002 Society for Neuroscience 0270-6474/02/222410864-07$05.00/0
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