Aristides Azevedo Pacheco Leão (August 3, 1914 in Rio de Janeiro – December 14, 1993 in São Paulo) was a Brazilian neurophysiologist, researcher and university professor. Leão discovered and described the spreading depression, which also became known as "the Leão wave". This depression is a reaction in the cerebral cortex that can be induced by touch or electric shock, although, more significantly, it occurs spontaneously in migraine and to some extent in epilepsy. It occurs not only in the brain, but in other neural structures. Leão was president of the Brazilian Academy of Sciences between 1967 and 1981 and defended scientists persecuted by the military dictatoship, besides having created scientific publications and having closed important scientific collaborations of the academy. Elected president emeritus of the institution, the academy's library now bears his name. He was awarded the Grand Cross of the National Order of Scientific Merit and was a full member of the Brazilian Academy of Sciences. Biography Leão was born on August 3, 1914, into a traditional family in Rio de Janeiro, the youngest of seven siblings. He never met his father, Manoel Pacheco Leão, who died shortly before Leão was born. His mother, the painter Francisca Azevedo Leão, raised the children alone, with the help of her brother-in-law, the biologist and director of the Rio de Janeiro Botanical Garden, Antônio Pacheco Leão, who assisted in the children's education. While living in a large house in the Laranjeiras neighborhood, the family was also helped by a British nanny of whom no records exist. Leão entered the São Paulo School of Medicine in 1932 at the age of 18. However, he contracted tuberculosis in his second year and had to suspend his studies for two years, while being treated in Belo Horizonte. When he recovered, he decided that he would like to work in scientific research and moved to the United States in 1941, where he was admitted to the graduate research program at Harvard Medical School. He received his master's degree in 1942 and his doctorate of science in 1943. Career In 1943, he became an adjunct researcher at Harvard's Department of Anatomy, where he identified the phenomenon of spreading depression, and although he had the opportunity to work in the United States, he preferred to return to Brazil in 1944, at the age of 32. Upon his return, he was appointed Specialized Technician of the Chair of Biological