When he came of age in the 1960s, the American artist Larry Poons was a student at the New England Conservatory of Music, training to become a professional musician. Attracted to the abstract art movements in New York, however, he left school to become a painter. Poons began with Op art paintings of circles and dots, and fame came quickly. He was hailed as an heir to the tradition of American painting, and was the youngest artist included in the Met Museum’s landmark exhibition of 1969, “New York Painting and Sculpture, 1940–1970.” Poons is now 83 and continues to break boundaries. Though his techniques have changed, his expressive energy has not. He creates large paintings with dazzling, frenetic brushstrokes. Works from five decades are gathered here, in Poons’s first London show in over 13 years. —E.C.