This superb and challenging program, the first of two honoring Chicago's internationally renowned Video Data Bank, represents video art at its conceptual purest, exploring the nature and limitations of the medium. Bruce Nauman's severe Stamping in the Studio (1968) runs 61 minutes, but its length is crucial to creating the sense of being uncomfortably trapped in a body (which is common to Nauman's art). A single upside-down overhead shot shows the artist alternating between stomps and lighter footsteps in a series of patterns, at first regular and then less so, suggesting the early music of Steve Reich. The sounds and the fact that his zigzagging trail never seems to repeat redirect the viewer's attention to tiny variations, at once intensifying and imprisoning perception. In Joan Jonas's Vertical Roll (1972) bars roll across imagery of a woman's body (as if a TV's vertical hold were shot), accompanied by clangs; finally a woman appears whole in front of the bars, the obsessive concentration on one “defect” of the medium suddenly transformed into the backdrop for a human presence. John Baldessari's Teaching a Plant the Alphabet (1972) is an amusingly perverse exercise in image-and-language disparity: a succession of cards, each showing a letter, is held up next to a plant, which doesn't appear to learn anything (unlike the plants Barbra Streisand talked to in the 1970 feature On a Clear Day You Can See Forever). Also showing: Richard Serra's Surprise Attack (1973) and Boomerang (1974). 114 min.