Left & Right Hemisphere Ping Pong

Last night I slept for quite a long period. I woke up and went back to sleep (w dreams) several times. Shortly before waking up again I experienced a sensation which I've experienced before.. I'm just wondering if anyone has any insight into this. It felt like my left and right hemispheres of my brain were lighting up, back and forth, one then the other, quite rapidly. Probably in a cycle of a few seconds. This happened several times and it was quite a pronounced sensation.. so much so that it has prompted me to do some research on what it could mean.