States of Consciousness
In the study of consciousness, we look for a common "altered" state to study. In humans, we study sleep.
We sleep in stages, each with distinct patterns of neurological behavior. (consult your textbook for the specifics of the stages).
REM sleep resembles the neural activity of waking or Stage 1 sleep. Although the EEG suggests an "active" brain, REM sleep is characterized by a lack of muscle tone. The EOG reveals that there is considerable electrical activity in the eye muscles. Once again, while this might suggest neural activity, there is a lack of muscle tone. For this reason, it is often referred to as "paradoxical" sleep.
We sleep in 90-minute stages. Earlier in the sleep cycle, we spend more time in Slow-Wave Sleep. As the cycle progresses, we spend more time in REM sleep towards morning.
Deprivation of SWS and REM Sleep results in a "rebound" effect. The organism spends more time the next noght in the deprived stage.
Jouvet determined that Slow Wave Sleep appeared to originate from that part of the brain stem that contained the Raphe Nuclei. These structures have a preponderance of serotonergic neurons. REM Sleep seemed to depend on another region of the brain stem, Locus Coeruleus whose major neurotransmitters are the catecholamines, specifically dopamine and norepinepherine. By severing neural connections at the mid-pontine level, the cortex is deprived of these sleep centers but not arousal centers. The animals experienced continual wakefulness.