[Duration of trace processes in the neocortex of rabbits].

Changes of pyramidal tract (PT) response after short tetanization, similar to natural stimulation conditions, were analysed in unanaesthetized and nonimmobilized rabbits. PT response recording revealed a long-term (1 h and more) potentiation of monosynaptic neocortical reactions. Predominant better expressed and more preserved increase of synaptic (N) component provides evidence to the conjecture that the basic mechanism of the long-term potentiation consists in the rise of efficiency of excitatory synaptic connections. Less protracted and differently directed changes of D-component permit to consider that excitability change of neurones may be only an additional mechanism of the long-term potentiation. Such features of neocortical long-term potentiation were revealed as its low-frequency depression (at test stimuli repetition) and its spontaneous restoration after depression.