TY - JOUR
T1 - Photoperiod and testosterone independently affect vocal control region volumes in adolescent male songbirds
AU - Gulledge, Cynthia C.
AU - Deviche, Pierre
PY - 1998/9/15
Y1 - 1998/9/15
N2 - Previously, we found that, unlike adults, adolescent male dark-eyed juncos (Junco hyemalis) maintained large Area X volumes despite having low plasma testosterone concentrations. Other studies indicate that photoperiod may act independently of testosterone to modulate vocal control region (VCR) volumes in adult songbirds. In the present study, we investigated the effects of testosterone and photoperiod on the volumes of four VCRs in adolescent male juncos. To test the hypothesis that VCR volumes in these males are testosterone independent, we treated birds exposed to short days with testosterone and later compared their VCR volumes with those of birds exposed to short days without testosterone. To examine whether photoperiod alone could affect VCR volumes independent of testosterone, we measured these volumes in photorefractory birds exposed to long photoperiod without testosterone. Administering testosterone induced singing, yet increased the volume of only one VCR, the robust nucleus of the anterior neostriatum (RA). In contrast, long photoperiod increased several VCR volumes (Area X, higher vocal center, and RA) despite low testosterone levels, but did not induce singing. Our results suggest a limited role for testosterone, but an important role for photoperiod, in controlling VCR volumes in adolescent male juncos. In addition, the results demonstrate that singing behavior can be induced in adolescent males without a concomitant increase in most VCR volumes.
AB - Previously, we found that, unlike adults, adolescent male dark-eyed juncos (Junco hyemalis) maintained large Area X volumes despite having low plasma testosterone concentrations. Other studies indicate that photoperiod may act independently of testosterone to modulate vocal control region (VCR) volumes in adult songbirds. In the present study, we investigated the effects of testosterone and photoperiod on the volumes of four VCRs in adolescent male juncos. To test the hypothesis that VCR volumes in these males are testosterone independent, we treated birds exposed to short days with testosterone and later compared their VCR volumes with those of birds exposed to short days without testosterone. To examine whether photoperiod alone could affect VCR volumes independent of testosterone, we measured these volumes in photorefractory birds exposed to long photoperiod without testosterone. Administering testosterone induced singing, yet increased the volume of only one VCR, the robust nucleus of the anterior neostriatum (RA). In contrast, long photoperiod increased several VCR volumes (Area X, higher vocal center, and RA) despite low testosterone levels, but did not induce singing. Our results suggest a limited role for testosterone, but an important role for photoperiod, in controlling VCR volumes in adolescent male juncos. In addition, the results demonstrate that singing behavior can be induced in adolescent males without a concomitant increase in most VCR volumes.
KW - Birdsong
KW - Junco
KW - Photoperiod
KW - Plasticity
KW - Testosterone
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U2 - 10.1002/(SICI)1097-4695(19980915)36:4<550::AID-NEU8>3.0.CO;2-V
DO - 10.1002/(SICI)1097-4695(19980915)36:4<550::AID-NEU8>3.0.CO;2-V
M3 - Article
C2 - 9740026
AN - SCOPUS:0031692088
SN - 0022-3034
VL - 36
SP - 550
EP - 558
JO - Journal of Neurobiology
JF - Journal of Neurobiology
IS - 4
ER -