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. 2014 Jan 6;7:51. doi: 10.3389/fnana.2013.00051

FIGURE 1.

FIGURE 1

Composite figure of photomicrographs (A,B) from rapid Golgi preparations of the motor cortex of 15-week-old human fetuses showing the developing gray matter neuronal composition, organization, and stratification. (A) Photomicrograph showing (at high magnification) the developing motor cortex gray matter neuronal composition and distribution through seven (1–7) different strata. At this age, the pyramidal cell plate formation is completed. It is composed only of pyramidal neurons of different sizes, anchored to first lamina, with smooth spineless apical dendrites, bodies without basal dendrites and unbranched descending axons, most of which have no yet reached the underlying white matter. The neuron’s size (apical dendrite length) denotes its arrival time at first lamina. (B) Montage of selected photomicrographs of the human motor cortex pyramidal plate showing (at a similar magnification) the neurons different sizes (apical dendrite length) and stratification. Their size ranges from the smaller superficial and last to arrive at first lamina and establish functional contacts (dendritic bouquets) with Cajal–Retzius cells to the larger, deeper and first ones to arrive. The thick horizontal axons (arrows) of Cajal–Retzius cells are also shown (A,B). Scale: 50 μm. Some of the larger, deeper, and older pyramidal neurons have started to develop short basal dendrites (B, P1) and a few dendritic spines (arrow heads) indicating the starting functional maturation of the motor cortex first (P1) pyramidal cell functional stratum. The functional maturation of this P1 pyramidal cell stratum is accompanied by the incorporation of its local microvasculature, protoplasmic astrocytes, and inhibitory neurons (Marín-Padilla, 2011). (B) Inset. Hematoxylin and eosin (H & E) preparation of the human motor cortex, at 15-week of age, showing the overall composition of its various components: first lamina, gray matter, subplate, white matter, matrix, paraventricular, and ependymal zones and the ventricle (V). (Modified from Marín-Padilla, 2011).