ON SOME PROPERTIES OF THE LONG-TERM HETER OSYNAPTIC DEPRESSION IN THECATS MOTOR CORTEX

It is shown that in the neocortex (like in the hippocampus) the long-t erm heterosynaptic depression (LTD) may exist. The effect appears as a long-term decrease of the probability of the monosynaptic responses i n the afferent input to the recorded neuron after the conditioning tet anization of the other afferent input to the same neuron. The main pro perties of the heterosynaptic LTD are its longevity, cooperativity and lack of input specificity. The heterosynaptic LTD in the unconditione d input and the LTP or the homosynaptic LTD in the conditioned input c an develop in parallel or independently of each other. It is supposed that the heterosynaptic LTD (like the LTP and the homosynaptic LTD) is Ca-dependent phenomenon and for its induction a certain level of depo larization of the membrane under the inactive (during conditioning) sy napses must be achieved, The heterosynaptic LTD may provide for the << contrasting>>, i. e. the relative increase of the efficiency of the ac tivated synapses, and probably be effective in such a phenomenon as fo rgetting.