i've never heard of the first thing you said...

the second thing you said... is clostest to the truth but i think you're missing information.



-when your awake your brain waves are fast, random and of low voltage (amp)
-when you're drowsy or relaxed the brain waves (called alpha waves) get a higher amplitude and cycle while in a slower and more regular manner. this is not sleep, this is just 'tired.'
-you'll soon reach theta waves. this is the official sign of sleep (also called sleep stage 1). theta waves lower in amplitude and become slightly more irregular than alpha.
-stage 2 of sleep is marked by short bursts of activity called sleep spindles. things called k complexes, show that, in this state, you're responsive to the outside world. if there's a loud noise or something a k complex might appear.
-stage 3 and stage 4 of sleep are very deep states of sleep, these patterns are called delta activity. they show more synchronized and slow-wave patterns. just know that amplitudes and cycles are significantly larger in these stages than with the others.

you dream in none of these... you dream in what's called REM.

REM is the state, where your brain waves look most like that of your waking brain waves. the amplitudes are lower and waves become more random. a sleep cycle might look like this (a cycle lasts around 90 minutes and you'll have 4-5 of them in a night).

awake -> sleep stage 1 -> sleep stage 2 -> sleep stage 3 -> sleep stage 4 -> sleep stage 3 -> sleep stage 2 -> sleep stage 1 -> REM

towards the end of the night REM will grow and the sleep stages will become less and less lengthy... in fact by the end of the night stage 4 seems to disappear and you end up spending almost all of your time in REM sleep.

hmmm

i don't know if 100% of your REM period is spent dreaming so what your teachers says might be true for certain people...

Nairne, James, S. Psychology: The Adaptive Mind. (3rd edition). 2003 Thomson Learning, Inc. Belmont, CA 94001-3098