Directed by Michael Rossato-Bennett. Rating unavailable.

Throughout the moving new documentary Alive Inside, senior citizen after senior citizen awakens from the near-catatonia of advanced Alzheimer’s or dementia to sing, tap feet, and even dance when an iPod plays music from his or her past. One man who spends his days slumped over in a wheelchair in an institution suddenly starts swaying and belting it out along with a gospel song; another woman, who still lives at home but can’t so much as differentiate the elevator’s up button from the down one, boogies around her living room to the Tremeloes’ “Fa La La, La La, La Le”.

They’re just part of the compelling evidence from quiet, unassuming social worker Dan Cohen’s accidental discovery about the ability of music to unlock some part of the identity of those lost to dementia. As neurologist and author Oliver Sacks explains it in the film, the place in our brain where we hold music, and musical memory, is the last to be ravaged by Alzheimer’s. “Music is a back door to the mind,” as he puts it.

There’s enough fascinating material for a documentary right there, but the brilliance of Michael Rossato-Bennett’s Sundance hit is that it artfully widens its lens to look at our cultural attitudes to warehousing seniors, and how a grim system developed to sedate the elderly with drugs and hide them away in institutions. The film makes it urgently obvious that there is a real person still “alive inside” even the farthest-gone patients.

With millions of people in North America languishing in these institutions, and a flood of millions more baby boomers set to enter them, these are pressing matters for all of us. That makes this essential viewing, but don’t worry: Rossato-Bennett keeps things upbeat, often funny, and ultimately optimistic that the system might be slowly changing.

In other words, as much as Cohen struggles to spread his message in the film, there is some hope that someone might be there to hook you up with Jack White on the iPod by the time it’s your turn for the nursing home.