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FIG 7. Summary diagram, superposed on AChE-stained coronal section through a telencephalon of 28-week-old human fetus constructed on the basis of our data and evidence from current literature. Thick black dashed lines delineate the first (C1) and second (C2) frontal crossroad area. The honeycomb pattern area denotes the deep periventricular system of fiber bundles; and circle with green dots developing fronto-occipital system, both containing SNAP-25 immunoreactive fibers. Colored lines denote systems of projection, association and commissural fibers passing through the crossroads (with triangles or quadrangles depicting cell bodies of origin), as follows: black = basal forebrain afferents; red = thalamocortical afferents; blue = callosal fibers; violet = corticofugal efferents. Note that both radially migrating neurons (black profiles along the yellow radial glial fiber) and tangentially migrating neurons (orange profiles) pass through the major crossroad (C1) area, which is located at the main predilection site of hypoxic-ischemic lesion in preterm infants.
