Fig. 5.

Axonal arbors of layer 2/3 pyramidal neurons are preferentially oriented along rows. A, The superimposed reconstructions of 5 axons (blue) and 10 dendrites (red) from layer 2/3 pyramidal neurons in a tangential projection plotted on an idealized barrel field composed of 400 × 400 μm barrels separated by 100 μm of septa (left panel). The density of neuronal processes was calculated and Gaussian smoothed (50 μm smoothing). Contours of 10 and 50% density of axon (blue) and dendrite (red) plotted on the idealized barrel field (right panel). Dendritic field span is rather limited compared with the axon. The extent of the axon is clearly longer along the row as compared with the arc. B, The laminar extent of the reconstructed dendrites and axons along the rows of the barrel field. Axonal arbors were reconstructed only within layer 2/3.C, The laminar extent of the reconstructed dendrites and axons along the arcs of the barrel field.