SOME AMBITIOUS exhibitions devoted to the history of video art have taken place in recent years—“Video Acts in 2002 at P.S. 1 Contemporary Art Center in New York, for example, or “Beyond Cinema” this past winter at the Hamburger Bahnhof in Berlin—but, curiously, they have predominantly been organized around loans from private collections. “First Generation: Art and the Moving Image, 1963–1986” represented a different sort of institutional commitment. For the past several years, Berta Sichel, director of the audiovisual department at the Reina Sofía, has been building a collection