Understanding of memory and learning is one of the major goals of neuroscientists and psychologists. The author first introduces the reader into the current state of knowledge of the mechanisms underlying memory by providing extensive reviews of contemporary results including behavioural approaches and molecular studies. He presents results of his group obtained by analysing elec- trical activity - including single neuron meassures. As a major experimental model the phenomenon of hippocampal long- term potentiation was studied. The so-called quantal analy- sis - a quantitative method - was applied to study mammalian brain plasticity. Short- and long-term synaptic plasticities were registered both in vivo and in vitro mammalian brain preparations. Results show the involvement of mainly presynaptic location in memory, however, the possible involvement of postsynaptic mechanisms is indicated by changes in quantal amplitude as shown by the author.