[Modular organization of callosal neurons in the sensomotor area of the cerebral cortex in the rabbit].

The density of distribution of callosal neurons in rabbit sensorimotor cortex was studied by means of horseradish peroxidase injection into the homotopic cortical area. The irregularity of density was evaluated visually and/or computed. Labelled callosal units were mostly small and medium-size pyramidal cells located primarily in layer III-IV and more rarely in layers V and VI. Layer III-IV revealed different patterns of labelled units grouping: in pairs, in 5-8 vertically situated cells, in clusters 120-200 micron wide, separated by areas with decreased density. The obtained results confirm previously made conclusion based on electrophysiological studies about the modular organization of callosal connections in sensorimotor cortex of rabbits.