Structural and immunochemical characteristics of the neuronal organization of field 4 of the sensorimotor cortex in cats.

Inhibitory interneurons in the cortex are regarded as an important intracortical module-forming factor. We report here our studies of the expression of three calcium-binding proteins in interneurons in the sensorimotor cortex of the cat. Calbindin-expressing non-pyramidal neurons were found to be distributed non-uniformly in layer III, forming large groups. Three-dimensional modeling showed that these groups formed continuous columns of width 400-1500 microm, which extended 6000-8000 microm mediolaterally both along the walls of the cruciate sulcus and on the free surfaces of the posterior and anterior sigmoid gyri. These data led to the hypothesis that these groups of inhibitory interneurons may create the conditions for selecting groups of efferent neurons within their areas and to recruit them into a single physiological act.