Former Grateful Dead drummer Mickey Hart is letting fans get in his head.
He has a new piece of gear on his latest tour.
It's a cap fitted with electrodes that capture his brain waves.
The data is used to direct the light show that's projected while he's jamming on stage.
The sensor-studded headgear was developed with a University of California-San Francisco neuroscientist.
Hart has been interested in brain issues since the late 1980s, when he saw his grandmother suffering from Alzheimer's disease.