Jerzy Konorski was one of the most eminent world leaders in research on brain physiology, the author of instrumental (Type II) conditioned refl ex theory and the founder of the Polish school of neurophysiology. Already as a student of medicine, Konorski discerned experimentally a new type of conditioned refl exes, which he called motor (Type II) as opposed to classic (Type I) salivary refl exes, studied by I.P. Pavlov. In 1928 he described, for the fi rst time, the specifi city of Type II refl exes and the methods of their training. In 1931–1933 he stayed in Pavlov’s famous laboratory in Petersburg. Since 1933 he was associated with the Nencki Institute of Experimental Biology, where after World War II, he created and became the Head of the Department of Neurophysiology, the research of which was devoted to the analysis of mechanisms controlling voluntary motor behavior. Konorski published more than 180 papers, among them three monographs, concerning principles of brain functioning. His passion for research, creativity and profound knowledge attracted many scientists from around the world who visited him and his Department. In recognition of his scientifi c achievements Konorski’s name was put on a strict list of candidates for Nobel Price. His death in 1973 was a great loss for both the Polish and world scientifi c community. His ideas are still appreciated and continue to inspire further research with the use of modern techniques.