Identification of three morphological subtypes of PCs in L6A of rat barrel cortex. (A) An unsupervised hierarchical cluster analysis was used to identify different clusters from 41 L6A PCs based on morphological parameters. The morphological parameters that were used: number of basal dendrite, total length of basal dendrites, average length of basal dendrites, dendritic horizontal fieldspan, dendritic vertical fieldspan, axonal length, axonal horizontal fieldspan, and relative soma depth. (B) Representative morphological reconstructions of a CT (green) PC, a CC PC (orange), and a putative CCla PC (blue); the somatodendritic domain is given in a darker, the axons are in a lighter shade. Barrels and layer borders are indicated in dashed gray lines. (C) 2D density maps of L6A CT PCs (left, n = 11), CC PCs (center, n = 17), and CCla PCs (right, n = 13). Dendrites are shown in red and axons are shown in blue. Horizontal distribution of L6 PC dendrites and axons are shown on the top, while vertical distributions are shown on the right. The curves indicate the average dendritic and axonal density distribution; bin size in the x- and y-axes: 50 μm in horizontal and vertical directions. Dashed lines indicate white matter position. (D) Summary data of several morphological properties of L6A CT (n = 11), CC (n = 17), and CCla (n = 13) PCs. Data are shown as box plots as described in the Materials and Methods section; individual points are color-coded as described above, ***P < 0.001, n.s. for P ≥ 0.05 for the Wilcoxon Mann–Whitney U test; n.s., not significant.