[Spread of excitation in the upper layers of the auditory cortex with the participation of intracortical interneuronal connections].

In the chronically isolated slab of the cat auditory cortex when lower layers were additionally undercut and one, two or three cortical layers under the pial surface remained structurally intact, impulse reactions of slab neurons to the intracortical stimulation applied on the other side of this additional undercut were investigated. High effectiveness of axo-dendritic and axo-spinal excitatory contacts formed by nerve elements of intracortical origin in the upper cortical layers was shown. Participation of geniculo-cortical fibres in the spread of excitation in the cortex through synaptic contacts in layer I with dendrites of pyramidal neurons of the lower layers is discussed. The possibility to generate polysynaptic excitatory reactions by neurons shows that in the isolated cortical slab with an undercut of the lower layers the complex interneuronal relations are retained.