have (got) something on the brain
informal Be obsessed with something: John has cars on the brain...- I have taken to shuffling about on the carpet with my rubber-soled shoes, distributing electric shocks because unlike the boys I don't have balls on the brain and rolling mouse balls along the carpet at a pin just doesn't interest me.
- I have a patient on the brain as well.
- Or at least acknowledge that they have it on the brain as much as men do.
See parent entry: brain