丘脑和大脑皮层之间的适当拓扑组织的神经连接对于丘脑功能是强制性的。丘脑皮质(TC)纤维生长在胚胎期开始,并在妊娠晚期完成,因此,人类新生儿出生时的丘脑具有成人功能分裂的近似传真。是否先天性新皮质异常(例如,大脑)影响人类的TC连接是未知的。这里,通过扩散MRI纤维束成像分析长期福尔马林固定的死后胎儿大脑,与年龄匹配的正常胎儿相比,我们发现丘脑亚区和TC纤维包裹的内囊的拓扑模式相似。然而,胎儿脑白质结构改变,包括更少/更少有组织的TC光纤和光辐射,TC纤维对皮质板的侵入要少得多-特别是在浅中央沟周围。15、23和26孕周(GW)正常胎儿大脑的弥散MRI纤维束成像显示每个丘脑分区的动态体积变化,提示丘脑与相应皮质的发育过程。此外,来自GW23和GW26正常胎儿大脑,可以描绘皮质板中的TC末端,以反映皮质板的累积进行性TC侵袭。相比之下,肝脑显示皮质板的TC侵袭显着减少。因此,我们的研究显示了在死后长期福尔马林固定的胎儿大脑中进行扩散MRI纤维束成像的可行性,以揭示在妊娠中期正常和间脑胎儿大脑中TC束与丘脑和新皮质生长协调的发育进展。
Proper topographically organized neural connections between the thalamus and the cerebral cortex are mandatory for thalamus function. Thalamocortical (TC) fiber growth begins during the embryonic period and completes by the third trimester of gestation, so that human neonates at birth have a thalamus with a near-facsimile of adult functional parcellation. Whether congenital neocortical anomaly (e.g.,
lissencephaly) affects TC connection in humans is unknown. Here, via diffusion MRI fiber-tractography analysis of long-term formalin-fixed postmortem fetal brain diagnosed as
lissencephaly in comparison with an age-matched normal one, we found similar topological patterns of thalamic subregions and of internal capsule parcellated by TC fibers. However,
lissencephaly fetal brain showed white matter structural changes, including fewer/less organized TC fibers and optic radiations, and much less cortical plate invasion by TC fibers - particularly around the shallow central sulcus. Diffusion MRI fiber tractography of normal fetal brains at 15, 23, and 26 gestational weeks (GW) revealed dynamic volumetric change of each parcellated thalamic subregion, suggesting coupled developmental progress of the thalamus with the corresponding cortex. Moreover, from GW23 and GW26 normal fetal brains, TC endings in the cortical plate could be delineated to reflect cumulative progressive TC invasion of cortical plate. By contrast,
lissencephaly brain showed a dramatic decrease in TC invasion of the cortical plate. Our study thus shows the feasibility of diffusion MRI fiber tractography in postmortem long-term formalin-fixed fetal brains to disclose the developmental progress of TC tracts coordinating with thalamic and neocortical growth both in normal and
lissencephaly fetal brains at mid-gestational stage.