She produced Britney's hit single "Gimme More" -- now singer/producer Keri Hilson is opening up to "Extra" about working on Britney's upcoming CD!

We caught up with Hilson backstage at F'N MTV, where she was a guest judge on last week's episode, and she told us that working with Spears is "completely normal." Keri is gearing up for the solo release of her own music; "In a Perfect World" drops on September 23rd.

Click on an image to view the BRITNEY SPEARS photo gallery!