[Spreading excitation in the upper (I-III) layers of an isolated strip of cat auditory cortex].

Lower layers of the isolated slab in the auditory cortex were cut, one, two or three cortical layers under the pial surface remaining intact. Impulse reactions of neurons to the intracortical stimulation applied on the other side of this additional cut were investigated in acute experiments on unanaesthetized immobilized cats. It was shown that stimulation of layer IV generated a flow of excitation ascending to the upper cortical layers and activating mono- and polysynaptically neurons of all layers through the vertical bundles of apical dendrites of pyramidal cells. Suggestion is made about an important role a large bundle of axons of layer III plays in the horizontal spread of excitation in the cerebral cortex.