Long-term posttetantic changes in the reaction of neighboring neurons in microsegments of the cat motor cortex.

The long-term postsynaptic changes of mono- and polysynaptic reactions of neighboring neurons of the MC were investigated following conditioning tetanization of different afferent inputs. Modifiable synapses were found both in the cells investigated and in local neuronal circuits which included the cells, i.e., possibly in interneurons. Alternating and concurrent conditioning of thalamocortical and corticocortical input showed that, depending upon the modality of the conditioned input, the tetanization parameters, the character of the distribution of the afferents, as well as on the character of local circuits which include excitatory and inhibitory interneurons, the effectiveness of synaptic inputs to neighboring neurons varies diversely, as a result of which a specific pattern of interneuronal connections forms in a microsegment of cortex, a pattern which may be maintained over the course of tens of minutes. It was found that modifiable synapses of different types may function simultaneously in one and the same micronetwork. The investigation may be of interest in developing models of memory and learning.