A Golgi study on the neuronal organization of the interhemispheric cortex in the mouse

The intrinsic neurons in the interhemispheric cortex (IHC) were studied by the rapid Golgi method in the young mouse. In each of the five layers of the IHC, a wide variety of intrinsic neurons were observed. They were classified into several groups according mainly to the patterns of axonal and dendritic distribution. The Cajal-Retzius cells were most frequently seen in layer I. The dendrites and axons of these neurons ran irregularly in the plane parallel to the pial surface of the IHC. Many neurons in layers II-V were observed to send their axons to layer I. Some of these neurons took the form of the inverted pyramidal neurons. The axons of some neurons in layers II, III and IV formed dense axonal plexuses usually in layer III and rarely in layer II. The dendrites of many neurons in layers IV and V extended into the cingulum. The stellate neurons embedded in the cingulum might be the dislocated neurons of layer V.