MODEL RELEASED. Sleep research. Man sleeping with the aid of eye shades. Electrodes can be placed on his head to measure his brain activity, which is recorded as an electroencephalogram (EEG) trace like the one seen on the eye shades. Study of the brain's activity during sleep has shown that there are five stages of sleep. The brainwaves slow with the onset of stage 1 where stress hormones drop as you close your eyes. Stage 2 is when consciousness is lost, digestion slows and hearing decreases. In the deep sleep of stages 3 and 4, slow brainwaves are produced and muscles relax and blood pressure and heart rate falls. Stage five is REM sleep with rapid eye movement, dreams and brain activity.