In the white matter of the human cerebrum, the majority of cortico-cortical fibers are of short range, connecting neighboring cortical areas. U-fibers represent connections between neighboring areas and are located in the white matter immediately deep to the cerebral cortex. Using gyrencephalic carnivore ferrets, here we investigated the neurochemical, anatomical and developmental features of U-fibers. We demonstrate that U-fibers were derived from neighboring cortical areas in ferrets. U-fiber regions in ferrets were intensely stained with Gallyas myelin staining and Turnbull blue iron staining. We further found that U-fibers were derived from neurons in both upper and lower layers in neighboring areas of the cerebral cortex and that U-fibers were formed later than axons in the deep white matter during development. Our findings shed light on the fundamental features of U-fibers in the gyrencephalic cerebral cortex. Because genetic manipulation techniques for ferrets are now available, ferrets should be an important option for investigating the development, functions and pathophysiological changes of U-fibers.

中文翻译：

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颅脑白鼬的皮质下U纤维的起源和发展。

在人类大脑的白质中，大多数皮层-皮层纤维是短距离的，连接相邻的皮层区域。U纤维代表相邻区域之间的连接，位于紧靠大脑皮层的白质中。在这里，我们使用人脑食肉动物雪貂研究了U纤维的神经化学，解剖学和发育特征。我们证明了U纤维是从雪貂的邻近皮质区域衍生而来的。雪貂中的U纤维区域用Gallyas髓磷脂染色和Turnbull蓝铁染色强烈染色。我们进一步发现，U纤维源自大脑皮层相邻区域上层和下层的神经元，并且在发育过程中，U纤维的形成要晚于深部白质中的轴突。我们的研究结果揭示了回旋型大脑皮层中U纤维的基本特征。由于雪貂的遗传操作技术已经问世，因此雪貂应该成为研究U纤维的发育，功能和病理生理变化的重要选择。