Dendrite bundles in lamina II/III of the rabbit neocortex

The present investigation systematically analyzes the course and arrangement of dendrites in lamina II/III of the visual and the motor cortex of the rabbit on the basis of Klüver-PAS stained 10 micron paraffin sections, 1 micron plastic-embedded semithin sections and ultrathin sections. In both areas the dendritic pattern of lamina II/III is characterized by vertical bundles reminiscent of the pattern in lamina IV/V. The bundles form in the upper half of lamina II/III. They consist mainly of apical dendrites from lamina II/III pyramidal cells and receive branches from dendrite bundles in lamina IV/V, i.e., branches from apical dendrites arising from lamina V pyramidal cells. Besides these features in common, the lamina II/III bundles in the visual cortex on the one hand and in the motor cortex on the other differ with regards to the size and shape of individual bundles as well as to the extent of connections with bundles in lamina IV/V.