There is a guy with the severe hand tremors that I associate with the degenerative neurological disorder.

The first thing you notice at Lucy Bowen McCauley's dance class for people with Parkinson's disease is the range of symptoms among the 15 people seated in a wide circle around the room.

But there's also a woman who moves with a stiff, awkward gait, a woman confined to a wheelchair and another man who shuffles and suffer from a pronounced, repetitive twitch of his mouth.

Their brains -- all our brains, actually -- love music, rhythm and dance in some primal way that creates joy and nourishes the body.

And then the music starts, and it is clear these people are united by more than just the bad break they share.

Especially a body wracked by tremors or slowed by herky-jerky arms and legs.

In a 2009 review of the relatively scant medical literature on dance as therapy for Parkinson's, researchers found it as effective as other forms of exercise and noted additional advantages:

Music may serve as an external cue that facilitates movement; dance involves stopping and restarting movement, something that is difficult for some people with Parkinson's;

dance requires multitasking; and dance is social -- an activity that fosters relationships and keeps people with Parkinson's from withdrawing from communities.

Then they all bow once more, together, toward the center of the circle and head outside into the rain. Thank you.

To end the class, they hold hands in a circle and, one by one, each bows theatrically to the person next to him.

It is a wordless gesture of thanks, of empathy, of support that is impossible to miss.