How do brain waves change as a sleeper progresses from stage 1 sleep to REM sleep? Multiple Choice Their amplitude decreases from stage 1 to stage 2, increases during stage 3, and then decreases again during REM sleep. Their frequency decreases from stage 1 to stage 2, increases during stage 3, and then decreases again during REM sleep. Their amplitude increases from stage 1 to stage 3 and then decreases during REM sleep. Their frequency increases from stage 1 to stage 3 and then decreases during REM sleep.