Aristides Azevedo Pacheco Leão (August 3, 1914, in Rio de Janeiro – December 14, 1993, in São Paulo[9]) was a Brazilian neurophysiologist, researcher and university professor.

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.

Elected president emeritus of the institution, he was awarded the Grand Cross of the National Order of Scientific Merit.

[21] In 1943, he became an adjunct researcher at Harvard's Department of Anatomy, where he identified the phenomenon of spreading depression,[22] 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.

[23][20] Upon his return, he was appointed Specialized Technician of the Chair of Biological Physics (1945) at the National School of Medicine of the Federal University of Rio de Janeiro.

Romualdo José do Carmo and Hiss Martins Ferreira [pt],[25] He continued his research into cortical spreading depression.

[34] After his mandatory retirement, he was named Laboratory Head Emeritus of the Department of Neurobiology of the Carlos Chagas Filho Biophysics Institute, where he remained for nine more years as a CNPq research fellow.

[37] The earliest origin of what has come to be known as spreading depression dates back to 1906, when Sir William Richard Gowers, in a lecture on epilepsy, noted that “a peculiar spreading disturbance of the nerve structures is evident” and that lasts for several minutes, something that was confirmed and described by Aristides Leão in this way:[38] While working on his PhD thesis at Harvard under the supervision of Hallowell Davis, Leão aimed to study "experimental "epilepsy".

To perform the experiment he opened anesthetized rabbit skulls and placed a row of silver electrodes in contact with the cortical surface, with two serving for stimulation.

[10] Somjen 2005 questions whether the ease with which this phenomenon can be caused did not cause other researchers to have observed it before Leão and dismissed it as an "annoying interruption of work" and goes on to say that this phenomenon intrigued him and became the main topic of Aristides' work, with his first article (Leão 1944a) demonstrating the basic characteristics that have been confirmed by other researchers.

[42] He also received posthumous tribute from the Brazilian Academy of Sciences, whose library today bears his name,[43][29] being elected president emeritus of this institution on December 20, 1993.

[45] According to Rodrigo Polito at Uol, Leão is the author of one of the most cited physiology articles in the world and dedicated his life to the development of science in his native country.