Neural substrates, including brain areas, differential gene expression and neuroendocrine basis, of migration are known. However, very little is known about structural changes in the brain that underlie the development and cessation of migration in long-distance avian migrants. Towards this, we investigated neuromorphological changes in the higher-order associative areas in male redheaded bunting (Emberiza bruniceps), which is a Palaearctic–Indian night migrant with wintering grounds in India. Photosensitive birds (8L:16D; SD) were exposed to stimulatory long days (16L:8D; LD), with controls retained on non-stimulatory short days. LD birds depicted shifts to, and sustained night-time activity as recorded by actograms. LD birds demonstrated increased body mass, fat deposition and testicular volume in keeping with the migratory phenotype. When LD birds had exhibited 10.0 ± 2.4 cycles of Zugunruhe (intense nighttime activity in captives, akin to night migratory flight in the wild), bird brains were fixed by transcardial perfusion, and changes in the neuronal morphometry of pallial, sub-pallial and hypothalamic brain regions studied using rapid Golgi technique with modifications, as used and validated in our laboratory. There were significant differences in both area and perimeter of soma in the visual hyperpallium apicale implicated in migratory orientation and the neuroendocrine control region for timing of migration, the mediobasal hypothalamus. We attribute these neuromorphometric changes in the soma area and perimeter to the photostimulated changes associated with the development of migration and reproductive phenotypes in redheaded buntings. It is suggested that changes in the neuronal plasticity in brain control regions parallel photoperiod-induced physiological responses.

迁移的神经基质，包括脑区域、差异基因表达和神经内分泌基础是已知的。然而，人们对长途鸟类迁徙的发育和停止的大脑结构变化知之甚少。为此，我们研究了雄性红发鹀（ Emberiza bruniceps ）高阶联想区域的神经形态变化，红发鹀是古北界-印度夜间迁徙动物，在印度越冬。感光鸟（8L：16D；SD）暴露于刺激性长日照（16L：8D；LD），对照组保留在非刺激性短日照下。LD鸟类描绘了活动图记录的夜间活动的转变和持续。LD鸟表现出体重、脂肪沉积和睾丸体积的增加，与迁徙表型一致。当LD鸟类表现出10.0±2.4个Zugunruhe周期（圈养的夜间强烈活动，类似于野外夜间迁徙飞行）时，鸟类大脑通过穿心灌注固定，大脑皮层、皮层下和下丘脑的神经元形态测量发生变化使用经过修改的快速高尔基体技术研究大脑区域，如我们实验室所使用和验证的。与迁移方向有关的视觉顶部皮层和迁移时间的神经内分泌控制区域（下丘脑内侧基底层）的体细胞面积和周长均存在显着差异。我们将体细胞区域和周长的这些神经形态变化归因于与红发鹀的迁徙和繁殖表型的发展相关的光刺激变化。这表明大脑控制区域神经元可塑性的变化与光周期诱导的生理反应平行。