Sophia loves a good belly combing

Sophia, a Maine Coon Cat, loves laying on her back on my lap to get a thorough combing of her neck, chest, belly, and inner thighs. She usually demands this treatment at least once per day. The usual routine is that she rolls over to get the combing, which puts her to sleep, and then she completes one full sleep cycle with the twitching and REM phase at the end. Then she gets up and gets a drink of water.