Yeah if you lie there and keep pushing out any thoughts that come into your mind (very difficult) so your thoughts are just empty while focusing on your breathing or heartbeat, you trick your body into thinking your asleep... and your body actually goes to sleep but your mind is still awake. Your body releases a chemical that paralyses you so you dont 'act out' your dreams (this is why you get sleep paralysis). You can feel your eyes flickering in their REM cycle, if you dont get freaked out at that point this is how you have 'out of body' experiences, lucid dreams and whatnot.
Delving into the depths of your subconciousness is fun.