on the/(one's) brain(redirected from on his brain)
on the/(one's) brain
Occupying one's sole or most prominent attention or interest; forming an obsession or preoccupation for one. Tom's just got football on the brain—he's not really interested in anything else. The history of this town has been on my brain ever since high school, so I'm delighted to finally have a creative outlet to explore those ideas.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
on the brain
Obsessively in mind: The coach has winning on the brain.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.