PMC

A: Higher magnification of ventral part of fasciculi gracilis and median part of fasciculi cuneatus. Left;Ventral part of fasciculi gracilis and median part of fasciculi cuneatus. Axons of right and left fasciculi gracilis and cuneatus fuse at the median part. fg; ventral part of fasciculi gracilis, fc; central part of fasciculus cuneatus, pt; pyramidal tract. Right; Higher magnification of the central part of fasciculi cuneatus. Several tangential axons (arrow heads) are noted at the median part of the fasciculi cuneatus. B: Higher magnification of ventral part of fasciculi cuneatus and gray commissure. a,b; specimens of Figure . From a triangular glial protrusion, a short lineal figure of glial tissue extends dorsally. Tangential axons (arrow heads) are noted in the glial tissue. c,d; contralateral specimens. Three to four axons enter the gray commissure vertically. Bundles of astrocytes extend along the axons from a triangular glial protrusion

Median pictures of posterior column. Left; A median picture of posterior column. A, b, and c frames indicate a, b, and c fields. fg; fasciculus gracilis, fc; fasciculus cuneatus, pt; pyramidal tract. a field; Posterior median sulcus and fasciculi gracilis. In the middle of the fasciculi gracilis, a fine lineal structure continues from the posterior median sulcus to the 3/4th depth of fasciculi gracilis (arrow heads). It disappears at the portion indicated by an arrow. b field; Ventral fasciculi gracilis, central part of fasciculi cuneatus, and bilateral pyramidal tracts. Axons of right and left fasciculi fuse without boundary structures at the midline. c field; Ventral fasciculi cuneatus, bilateral pyramidal tracts and gray commissure. A triangular protrusion of glial tissue is noted at the commissure (arrow). It deviates a little from the commissure midline. A short fine lineal tissue (arrowhead) extends from the protrusion

Sagittal slices of region masks for the arcuate and uncinate fasciculi. The arcuate fasciculus is displayed in white, and the uncinate fasciculus is displayed in blue.

Age is positively associated with fiber density and cross-section of major white matter tracts.
Note. FDC = fiber density and cross-section; SLF = superior longitudinal fasciculi; ILF = inferior longitudinal fasciculi; IFOF = inferior fronto-occipital fasciculi; CST = corticospinal tracts; Fmin = forceps minor; Fmaj = forceps major; CCbod = callosal body; UF = uncinate fasciculi; CING = cingulum bundles; ATR = anterior thalamic radiations.