Comparative morphology of three types of projection‐identified pyramidal neurons in the superficial layers of cat visual cortex

The morphology and dendritic organization of corticocortical neurons in the superficial layers of area 18 that project to area 17 were studied by intracellular injection of lucifer yellow in the fixed‐slice preparation. This corticocortical population contains primarily standard pyramidal cells, but occasional nonpyramidal, modified, fusiform, star, and inverted pyramidal cells were also seen. All cell types were present throughout layer 2 and in the upper and middle parts of layer 3. Standard pyramidal cells were found exclusively in lower layer 3. The mean somatic area of the area 17 projecting neurons was 251 μm2. The width of basal dendritic fields was correlated to cell size for standard pyramidal cells but not for the other cell types.