For 20 years before his mother’s death in 2004 at age 89, actor Peter Gallagher witnessed her gradual descent into the oblivion that characterizes Alzheimer’s disease. Slight memory lapses in the shy, fiercely intelligent Mary Ann O’Shea Gallagher gave way over time to a profound disconnection from the present, interrupted occasionally by breakthrough moments of clarity. “All of a sudden there would be a twinkle, a warmth and look of great love in her eyes. Then I would see fear in her eyes that I had never seen, as if the landmarks that were so familiar to her were now foreign,” recalls Gallagher, 53, a film and Broadway veteran who most recently starred as public defender Sandy Cohen on the hit TV series The O.C. Saddened and yet inspired by his mother’s fight, Gallagher immersed himself in the search for a cure. He serves on the National Advisory Council of the Alzheimer’s Association, organizes Los Angeles-chapter fundraisers, and participates in fundraising Memory Walks, all with the unshakable belief that treatments for this devastating disease will be found before too long. Until that happens, the actor won’t give up. “It makes me feel less powerless,” he says. “I do it for my mother. It’s the best way I can think of to honor her.”