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See detailIn vivo MR imaging of the seasonal volumetric and functional plasticity of song control nuclei in relation to song output in a female songbird
Van Meir, V.; Pavlova, D.; Verhoye, M. et al

in Neuroimage (2006), 31(3), 981-992

In temperate zone songbird species, seasonal plasticity in the morphological and functional state of brain regions involved in song production occurs in association with seasonal changes in song output ... [more ▼]

In temperate zone songbird species, seasonal plasticity in the morphological and functional state of brain regions involved in song production occurs in association with seasonal changes in song output. Following MHCl2-injections in HVC (used as proper name) of female starlings, in vivo tract-tracing by Manganese Enhanced-Magnetic Resonance Imaging (ME-MRI) provided repeated measures of the volume of two HVC targets, the nucleus robustus arcopallii (RA) and area X, along with measures of the activity of the caudal motor pathway and rostral basal-ganglia pathway that control singing. Mn2+- labeling (volume labeled and signal intensity) of both nuclei was dramatically reduced in July (post-breeding season) when birds did not sing, compared to March (breeding season) when birds produced song. Seasonal changes in telencephalon volume did not exceed 4% and were not significant but were surprisingly correlated with individual measures of song rate and song bout length. Although individual song rates were variable in March, all MnCl2-injections led to a reliable labeling of area X and RA. In July, delineation of area X was only possible in two birds and RA could be delineated in 50% of the population; its volume had decreased by 46% as compared to March. The birds in which RA could be delineated in July had in March a higher activity of the HVC to area X projection as reflected by the total amount of Mn2+ accumulated in area X, which suggests unexpected relationships between the two types of HVC projection neurons. (c) 2006 Elsevier Inc. All rights reserved. [less ▲]

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See detailEffect of age and testosterone on autumnal neurogenesis in male European starlings (Sturnus vulgaris)
Absil, Philippe ULg; Pinxten, R.; Balthazart, Jacques ULg et al

in Behavioural Brain Research (2003), 143(1), 15-30

The male European starling (Sturnus vulgaris) is an open-ended learner that increases its repertoire throughout life. In parallel, the volume of hi-h vocal center (HVC) is larger in older birds than in ... [more ▼]

The male European starling (Sturnus vulgaris) is an open-ended learner that increases its repertoire throughout life. In parallel, the volume of hi-h vocal center (HVC) is larger in older birds than in yearlings. We labeled with the thymidine analog 5-bromodeoxyuridine (BrdU) the cells that are generated during the fall in the brain of adult males that were 2 or more years old and in yearling males that were treated with exogenous testosterone (T) or kept intact before BrdU administration. In all subjects, the singing rate was recorded and BrdU-Iabeled cells were quantified in HVC, in proliferative areas of the ventricular zone (VZ) and in auditory regions. BrdU-containing cells were observed in all brain regions investigated. They were significantly more numerous in the VZ of the T-treated yearlings than in any other group. In older birds, a reduced number of labeled cells was specifically observed in the VZ close to the anterior commissure. No group difference was detected in auditory processing areas or in HVC. These data show for the first time a positive influence of T on the production of new cells at the VZ level in a male songbird and a decrease of this process with age. Furthermore, in T-treated birds, a correlation was observed between the HVC volume and the number of differentiated (round) BrdU-positive cell numbers in HVC on the one hand and song rate on another hand supporting the notion that singing activity is causally related to the T-induced growth of this song control nucleus. (C) 2003 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailEffects of testosterone on Reelin expression in the brain of male European starlings
Absil, Philippe ULg; Pinxten, R.; Balthazart, Jacques ULg et al

in Cell & Tissue Research (2003), 312(1), 81-93

Reelin, a large glycoprotein defective in reeler mice, is assumed to determine the final location of migrating neurons in the developing brain. We studied the expression of Reelin in the brain of adult ... [more ▼]

Reelin, a large glycoprotein defective in reeler mice, is assumed to determine the final location of migrating neurons in the developing brain. We studied the expression of Reelin in the brain of adult male European starlings that had been treated or not with exogenous testosterone. Reelin-immunoreactive cells and fibers were widely distributed in the forebrain including areas in and around the song control nucleus, HVC. No labeling was detected in other song control nuclei with the exception of nucleus uvaeformis, which was delineated by a dense cluster of Reelin-immunoreactive perikarya. Reelin is thus expressed in areas incorporating new neurons in adulthood, such as HVC. Reelin expression was sharply decreased by testosterone in HVC, nucleus uvaeformis and dorsal thalamus but not in other brain regions. These results are consistent with the idea that seasonal changes in Reelin expression modulate the incorporation of neurons within HVC. The presence of Reelin in other brain areas that do not incorporate new neurons in adulthood indicates, however, that this protein must play other unrelated roles in the adult brain. Additional studies should now be carried out to determine the specific role played by this protein in the seasonal plasticity of the songbird brain. [less ▲]

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See detailContext-dependent effects of castration and testosterone treatment on song in male European starlings
Pinxten, R.; De Ridder, E.; Balthazart, Jacques ULg et al

in Hormones & Behavior (2002), 42(3), 307-318

Most seasonally breeding songbirds display dramatic seasonal fluctuations in plasma testosterone (T) levels and mate attraction behaviors, including song. However, males of some songbird species, such as ... [more ▼]

Most seasonally breeding songbirds display dramatic seasonal fluctuations in plasma testosterone (T) levels and mate attraction behaviors, including song. However, males of some songbird species, such as the European starling (Stumus vulgaris), continue to sing at high levels after the breeding season, when T levels are basal. In male starlings song during the breeding season functions mainly to attract mates, whereas song during the nonbreeding season appears unrelated to reproduction. This suggests that song produced in a context unrelated to female courtship, unlike song directed toward females, is not regulated by plasma T. In captive males housed in large outdoor aviaries we explored the relationship between plasma T and song produced during the breeding season within and outside a courtship context. This was achieved by determining the effects of castration and subsequent T treatment on song and mate attraction behaviors in both the presence and the absence of a female. Compared to intact males, castrated males did not show reduced song activity in the absence of a female for at least 6 months after the operation, strongly suggesting that the expression of noncourtship song is not regulated by plasma T. Likewise, we found that experimentally elevating T levels in castrated males did not affect noncourtship song rates. However, control castrated males receiving empty implants tended to show reduced noncourtship song rates after implantation. This may have been due to a suppressive effect caused by the presence of the T-implanted castrated males in the same aviary. In contrast, courtship singing was clearly controlled by plasma T: it was abolished by castration and restored by subsequent T replacement when males were housed both individually and in a group situation. High plasma levels of T also appeared necessary for the activation of three other behavioral traits critical for mate attraction, namely, nesthole occupancy, spending time (singing) in a nesthole, and carrying green nesting material into a nesthole. (C) 2002 Elsevier Science (USA). [less ▲]

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