It says in the Babylonian Talmud, Tractate Brachot 5b “a prisoner cannot free himself from prison” – meaning a person cannot correct his deeds after his death, and therefore learning mishnayos in this world brings great benefit to the deceased.
Before learning the mishnayos for the elevation of the soul, a person should say the name of the deceased and that of his mother, and declare that this study is dedicated to the elevation of his soul.