turn someone’s brain—
1. cause mental disorder:
- The only possible explanation was that the poor girl’s illness and the loss of her lover had turned her brain.
2. make a person wildly agitated or distraught:
- Too much of this sort of work turns your brain.
turn someone’s head—
1. cause a person to have too high an opinion of oneself:
- She is a famous actress but she has not allowed success to turn her head.
2. cause a person to become infatuated:
- You have been making serious love to Patty, and have turned the poor girl’s head.
3. create a sensation of giddiness:
- To look down from a great height is enough to turn one’s head.
Note: The expression does not correlate in meaning with the phrase turn heads—strongly impress people (by looking very attractive):
- Cher turned heads when she appeared at the ceremony in a dress that left little to the imagination.