New Delhi, May 13 -- In a quiet community hall in Mumbai, 70-year-old Hari stands surrounded by a group of men and women, some older, some younger, all marked in different ways by Parkinson's disease. A tabla beat pulses steadily in the background. Hari's arms float through the air, his fingers curled into soft gestures, his feet tapping in sync with the rhythm. This simple act of moving joyfully and purposefully is a small triumph. Just a few months ago, Hari could barely walk across his living room without the fear of falling.

Hari, like many with Parkinson's, has faced a steady erosion of not just motor control but identity itself. "It wasn't the tremors or the falls that broke me," he says. "It was the loss of who I used to be." But ...