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FIG 2. During the fetal lamination stage (16–24 weeks of gestation), the basic fiber-architectonic pattern is characterized by predominantly tangential organization (axon strata) and prominent crossroads (C1–C6, dashed squares) of projection, association, and commissural fibers, as revealed on coronal (A–C and E–I) and horizontal (D) sections; Nissl-stained (A), AChE-stained (B, D, F, G), PAS-AB-stained (E), and T1-weighted MR imaging sections (C, H, I); in fetuses aged 16 weeks (D), 18 weeks (G, H), 19 weeks (A, E), 21 weeks (B, C), and 24 weeks (F). After 28 weeks of gestation, MR imaging signal intensity changes with consequent blurring of laminar pattern, as revealed by T1-weighted MR coronal section through the cerebrum of 30-week-old fetus (I). Asterisks in C and H mark the periventricular-subventricular fiber system.
