Fig. 9.

Bottom. Density of corticospinal projections from the hand area of the primary motor cortex to C8–Th1 in the 2.5-month-old, 5-month-old, and 3-year-old (case 3) cases. For each monkey, four sections have been selected in each half-segment (R, rostral; C, caudal); these sections had a distribution that most closely matched the mean value on the 6–12 sections taken from that half-segment (see Materials and Methods). The color scale corresponds to the five equal-density ranges of the window of termination (see Figs. 1, 2). The region of lamina IX occupied by the hand and finger motor nuclei (see Fig. 3) is delineated by a white line. Note the caudal-to-rostral increase in density of labeling among the hand muscle motor nuclei.