[Long-term changes in the efficiency of excitatory synaptic transmission in the thalamocortical networks evoked by microstimulation of the neocortex].

The long-term posttetanic modifications of the efficacy of excitatory synaptic connections were studied in auditory thalamo-cortical assemblies. We demonstrate that intracortical microstimulation--ICMS (high frequency pulses of 5 uA), which activated a small group of cortical neurons, produced long-term (at least 30 min) modifications (potentiation-LTP and depression-LTD) of the efficacy of excitatory monosynaptic transmission between numerous elements of thalamo-cortical network. Effectivity of "common input" also was potentiated or depressed. The amount of effective connections between neurons located in stimulated and nonstimulated loci of the cortex increased after ICMS. Some neurons in the network were favourable for inducing LTP. The efficacy of the synapses formed by terminals of one axon on different cells can be modified variously. The efficacy of the synapses formed by neurons from different loci of auditory cortex and MGB on the same target cell also can be modified variously.