Songbirds learn their song during a sensitive period of development associated with enhanced neural plasticity. In addition, in open-ended learners such as canaries, a sensitive period for sensorimotor vocal learning reopens each year in the fall and leads to song modifications between successive breeding seasons. The variability observed in song production across seasons in adult canaries correlates with seasonal fluctuations of testosterone concentrations and with morphological changes in nuclei of the song control system (SCS). The sensitive periods for song learning during ontogeny and then again in adulthood could be controlled by the development of perineuronal nets (PNN) around parvalbumin-expressing interneurones (PV) which limits learning-induced neuroplasticity. However, this relationship has never been investigated in the context of adult vocal learning in adult songbirds. Here we explored PNN and PV expression in the SCS of adult male Fife Fancy canaries in relation to the seasonal variations of their singing behaviour. We found a clear pattern of seasonal variation in testosterone concentrations and song production. Furthermore, PNN expression was significantly higher in two specific song control nuclei, the robust nucleus of the arcopallium (RA) and the Area X of the basal ganglia, during the breeding season and during the later stages of sensorimotor song development compared to birds in an earlier stage of sensorimotor development during the fall. These data provide the first evidence that changes in PNN expression could represent a mechanism regulating the closing-reopening of sensitive periods for vocal learning across seasons in adult songbirds.

中文翻译：

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成年金丝雀（Serinus canaria）的神经周围神经网络和歌曲学习的季节性变化。

鸣禽在与神经可塑性增强相关的敏感发育时期学习其歌曲。此外，在诸如金丝雀这样的开放式学习者中，每年秋天，感官声乐学习的敏感时期每年重新开放，并导致在连续繁殖季节之间改变歌曲。在成年金丝雀的整个季节中，歌曲制作过程中观察到的变异性与睾丸激素浓度的季节性波动以及歌曲控制系统（SCS）的细胞核形态变化相关。在个体发育期间以及成年后再次学习歌曲的敏感时期，可以通过表达小白蛋白的中间神经元（PV）周围的神经周围神经网络（PNN）的发展来控制，这限制了学习诱发的神经可塑性。然而，在成年鸣鸟的成年声乐学习中从未研究过这种关系。在这里，我们探讨了成年男性Fife Fancy金丝雀的SCS中PNN和PV的表达与他们歌唱行为的季节性变化之间的关系。我们发现睾丸激素浓度和歌曲产生存在明显的季节性变化模式。此外，与鸟类中的鸟类相比，在繁殖季节和感觉运动歌曲发展的后期，在两个特定的歌曲控制核中，arcopallium（RA）的健壮核和基底神经节的Area X的PNN表达明显更高。在秋季感觉运动发展的早期阶段。