07 Civic EX Automatic

I've been having this weird transmission issue with my car. Everytime I drive down a steep hill and lightly press the break to keep the car from accelerating, the RPMs drop then jump back up and it revs like its almost downshifting the tranny for me, as if it were a manual. It almost feel likes its having a problem shifting between gears. Im clueless to know if this is normal or there is something wrong with the transmission.