Susan Gustafson had suffered dementia for several years when her family decided she needed around-the-clock care and moved her into a memory care unit at an assisted living facility in Costa Mesa, Calif.

Her daughter, Nancy Gustafson, a retired opera singer and artist-in-residence at Northwestern University in Illinois, says when she visited her mom for the first time, she was devastated. "She was sitting in her wheelchair with her head down at a breakfast table," Nancy Gustafson remembers. "I'll never forget — looking so sad and looking so lost and so confused." Her mom answered "Yes" and "No" to questions, but Gustafson felt she didn't really understand and answered just to be polite. She says her mother "couldn't put two words together" and didn't recognize her. She tried looking at family pictures with her, in hopes that it would stir her mother's memory.

"I'd go through photo albums with her ... and she wouldn't show any recognition of anyone," Gustafson says. After that, Gustafson visited her mom every month. During a visit in October a few years ago, she got an idea about how to make a meaningful connection with her. She wheeled her mom next to the piano in the living room of the care facility and started to play and sing. "Mom is singing with me!" She doesn't remember exactly what Christmas carols she sang, but she says she included some of her mother's favorites, such as "Hark! The Herald Angels Sing," "Deck the Halls With Boughs of Holly" and "Angels We Have Heard On High." As soon as she started, her mother started singing with her. "I caught her out of the corner of my eye," she says. "And I just wanted to jump up and run out to call my sister immediately, saying, 'Mom is singing with me!'"

Gustafson may have been elated, but her mom had a slightly different reaction. Apparently she didn't approve of her daughter's piano skills. After about 15 minutes, Gustafson turned to look at her mom, who said: "You know that's not so good." Gustafson remembers laughing hard. "That's exactly what my mother would have said to me had she been without Alzheimer's," she says. "She would have said that 30 years ago." Though Gustafson is a professional singer, she concedes that her piano playing isn't that great. She promised to try harder and not hit the wrong chords. They sang for another 20 minutes, and "as we finished, I turned and looked at her and she said, 'That's much better.' " Gustafson was floored. "I looked at her and I said, 'Mom, you know we're really getting good.' " Then she told her mom that Christmas was coming, and "if we practice enough we could go to the shopping center, put out a cup and earn some money."

Gustafson remembers her mom laughed and said "Ha ha! The Gustafson Family Singers!" And at that moment, their lives and relationship changed, Gustafson says, because all of a sudden "not only was she relating to me and she was cracking a joke, but she knew our last name and she knew that I was related to her." "Music has a deep hold over us" Gustafson's story is heartwarming but not surprising to Nina Kraus, a researcher and neuroscientist who directs the Auditory Neuroscience Laboratory at Northwestern University. She says sound is evolutionarily ancient and deeply rooted in the nervous system. "The memories that we make, those sound-to-meaning connections that we have and that we've made throughout our lives, are always there," she explains. "It's a matter of being able to access them."

Because of this very tight inherent connection between memory systems in the brain and the auditory brain, just listening to "familiar sounds will evoke memory," she says. "I like to think of music as a jackpot in engaging how we think and feel and remember and move with sound." It's remarkably common, she says, for music to evoke memories that have been lost. In fact, the therapeutic power of music that Gustafson inadvertently stumbled on is being offered as a treatment to patients with dementia in many places. And it's the subject of a growing field of research. One researcher looking into the role of music in the brain is Maria Chait with the University College London Ear Institute, who led a small study looking at brain responses to both familiar and unfamiliar songs. The goal of the study, published in October, was to quantify just how quickly the brain can respond to familiar, meaningful music.