Excitatory interactions in neuronal networks which include cells of the auditory cortex and the medial geniculate...

The use of the method of cross-correlation analysis to elucidate the interactions between simultaneously recorded neurons from various loci of the auditory cortex (AC) and the medial geniculate body (MGB) has made it possible to identify the following characteristics of the functional organization of the excitatory interactions in the thalamocortical neuronal networks: the interdependant impulse action of neurons located at various loci of the AC and MGB was determined by reciprocal excitatory connections; the efficiency of the connections between neurons of the AC, 400-500 microns apart, and between tonotopically associated neurons of the AC and MGB was approximately identical (associations were identified in 12% of the cases); the "divergent" properties of the MGB (AC) neurons were manifested in the fact that one and same neuron could simultaneously excite both neighboring cells and neurons from one or several loci of the AC (MGB); the "convergent" properties of the AC and MGB neurons were manifested in the fact that cells located at various loci of the AC and MGB simultaneously excited one neuron. The results make it possible to explain the deviations observed in the investigation of RF of neurons of the AC and MGB from the principle of tonotopical organization. It is hypothesized that the character of the organization of the excitatory connections in the thalamocortical networks may promote the creation of the necessary conditions for the modification of the efficiency of synapses between all of the elements of the network during the stimulation of individual elements.