Ball Gregory F, Riters Lauren V, Balthazart Jacques
Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland 21218, USA.
Front Neuroendocrinol. 2002 Apr;23(2):137-78. doi: 10.1006/frne.2002.0230.
Seasonal changes in the brain of songbirds are one of the most dramatic examples of naturally occurring neuroplasticity that have been described in any vertebrate species. In males of temperate-zone songbird species, the volumes of several telencephalic nuclei that control song behavior are significantly larger in the spring than in the fall. These increases in volume are correlated with high rates of singing and high concentrations of testosterone in the plasma. Several song nuclei express either androgen receptors or estrogen receptors, therefore it is possible that testosterone acting via estrogenic or androgenic metabolites regulates song behavior by seasonally modulating the morphology of these song control nuclei. However, the causal links among these variables have not been established. Dissociations among high concentrations of testosterone, enlarged song nuclei, and high rates of singing behavior have been observed. Singing behavior itself can promote cellular changes associated with increases in the volume of the song control nuclei. Also, testosterone may stimulate song behavior by acting in brain regions outside of the song control system such as in the preoptic area or in catecholamine cell groups in the brainstem. Thus testosterone effects on neuroplasticity in the song system may be indirect in that behavioral activity stimulated by testosterone acting in sites that promote male sexual behavior could in turn promote morphological changes in the song system.
鸣禽大脑的季节性变化是在任何脊椎动物物种中所描述的自然发生的神经可塑性最显著的例子之一。在温带鸣禽物种的雄性中，控制鸣叫行为的几个端脑核的体积在春季显著大于秋季。这些体积的增加与高鸣叫率和血浆中高浓度的睾酮相关。几个鸣叫核表达雄激素受体或雌激素受体，因此有可能睾酮通过雌激素或雄激素代谢产物起作用，通过季节性调节这些鸣叫控制核的形态来调节鸣叫行为。然而，这些变量之间的因果联系尚未建立。已经观察到高浓度睾酮、扩大的鸣叫核和高鸣叫行为之间的分离。鸣叫行为本身可以促进与鸣叫控制核体积增加相关的细胞变化。此外，睾酮可能通过在鸣叫控制系统之外的脑区起作用来刺激鸣叫行为，比如视前区或脑干中的儿茶酚胺细胞群。因此，睾酮对鸣叫系统神经可塑性的影响可能是间接的，因为睾酮在促进雄性性行为的部位起作用所刺激的行为活动反过来可能促进鸣叫系统的形态变化。
