[Cortico-cortical connections in the motor cortex of the brain; a study using the peroxidase method]

Using a method based on retrograde axonal transport of horse-radish peroxidase (HRP), the cortico-cortical afferents of the motor cortex were studied. After enzyme injection into the posterior sigmoideus gyrus, the HRP product was found in the first and the second somatic sensory areas and in parietal cortex (fields 5a, 5b). The HRP-positive neurons occurred in layers II, III and V of the cortex and belonged to the pyramidal cells.