Division of Newborn Medicine, Department of Medicine, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA.
Cereb Cortex. 2012 Feb;22(2):455-64. doi: 10.1093/cercor/bhr126. Epub 2011 Jun 13.
Cerebral axonal connections begin to develop before birth during radial migration in each brain area. A number of theories are still actively debated regarding the link between neuronal migration, developing connectivity, and gyrification. Here, we used high angular resolution diffusion tractography on postmortem fetal human brains (postconception week (W) 17-40) to document the regression of radial and tangential organization likely to represent migration pathways and the emergence of corticocortical organization and gyrification. The dominant radial organization at W17 gradually diminished first in dorsal parieto-occipital and later in ventral frontotemporal regions with regional variation: radial organization persisted longer in the crests of gyri than at the depths of sulci. The dominant tangential organization of the ganglionic eminence at W17 also gradually disappeared by term, together with the disappearance of the ganglionic eminence. A few immature long-range association pathways were visible at W17, gradually became evident by term. Short-range corticocortical tracts emerged prior to gyrification in regions where sulci later developed. Our results suggest that the regional regression of radial organization and regional emergence of fetal brain connectivity proceeds in general from posterodorsal to anteroventral with local variations.
大脑轴突连接在每个脑区的放射状迁移过程中于出生前开始发育。关于神经元迁移、发育中的连接和脑回形成之间的联系，仍有许多理论在积极争论。在这里，我们使用高角度分辨率扩散轨迹技术对死后胎儿人脑（妊娠后第 17 周到第 40 周）进行了研究，记录了放射状和切线组织的回归，这些组织可能代表了迁移途径，以及皮质间连接和脑回形成的出现。第 17 周时占主导地位的放射状组织首先在前顶枕部和后逐渐减少，在腹侧额叶区域也存在区域差异：在脑回的隆凸处，放射状组织的持续时间比在脑沟的深处更长。第 17 周时神经节隆起的主要切线组织也随着神经节隆起的消失而逐渐消失。在妊娠期末，一些不成熟的长距离联络通路变得可见，逐渐变得明显。在以后出现脑沟的区域，短程皮质间束在脑回形成之前就已经出现。我们的结果表明，胎儿大脑连接的放射状组织的区域回归和区域出现总体上从后向前进行，存在局部差异。
