Hart is best known for the rhythms he created with the Grateful Dead. But lately, he's more concerned with a different kind of rhythm.
The rhythm in the brain, finding out what rhythm central sounds like," Hart said. "It's the master clock. It makes everything go."
In his years on the road, hart says he always felt music had a special power over the brain to heal and awaken it.
One day, that hunch became a certainty.
"My grandmother, who had Alzheimer's, advanced Alzheimer's, and she couldn't speak, she hadn't spoken in over a year, I played a drum for her, and she spoke my name," Hart said. "She started to become connected again -- to become verbal."
The improvement lasted only a moment, but Hart says it changed his direction in life forever.
Now Hart is participating in an experiment where he wears an EEG cap and each of the electrodes are help detect the very subtle signals that have rhythmic activity being generated by the neurons in his brain.
Hart is taking this gear on tour with him so live audiences can watch his neurons pulse as he plays the drums.
It's the beginning of something much bigger.
It all started by accident, when Hart was asked to do a speaking engagement with UCSF neuroscience professor Adam Gazzaley. Gazzaley was studying how to retrain the brain using video game technology. But using that technology to look at the brain was an entirely new idea.
"This concept that rhythm might be therapeutic has been around for a long time; there's just really not studies that have carefully controlled a rhythmic experiment and looked for changes in the brain," Gazzaley said.
Only now are computers powerful enough to show those changes live.
Now, Hart is the first subject in a new experiment: seeing his own brainwaves as he drums. He tries to control the rhythm of his brain by changing the rhythm of the music.
"I move into its time, and try to do what it's doing and go with it and I try to entrain with it and stay there as long as possible, and then move it slightly, you know, turn it to the right, turn it to the left," Hart said.
Hart says it's a dance, one Gazzaley says could hold great promise for patients whose brains have lost their natural rhythm.
"If we could help reorganize those rhythms, re-entrain them, then hopefully we can improve cognition along with that," Gazzaley said.
A drug of sorts with huge medicinal promise -- that for Hart is also recreational.
"You might say it gets you high because you're connecting with the real you," Hart said.