Psychology2016

Consciousness 147

REM SLEEP: PERCHANCE TO DREAM? When a person in stage R is awakened, he or she
almost always reports being in a dream state (Shafton, 1995). REM sleep is, therefore, asso-
ciated with dreaming, and 90 percent of dreams actually take place in REM sleep. People
do have dreams in the other non-REM sleep stages, but REM sleep dreams tend to be more
vivid, more detailed, longer, and more bizarre than the dreams of NREM sleep. NREM
sleep dreams tend to be more like thoughts about daily occurrences and far shorter than
REM sleep dreams (Foulkes & Schmidt, 1983; Takeuchi et al., 2003). Fortunately, the body is
unable to act upon these dreams under normal conditions because the voluntary muscles
are paralyzed during REM sleep, a condition known as sleep paralysis. (This is why you
sometimes have a dream in which you are trying to run or move and can’t—you are par-
tially aware of sleep paralysis.)

WHAT IS THE PURPOSE OF REM SLEEP? Why two kinds of sleep? And why would REM
sleep ever be considered restful when the body is almost awake and the brain is so
active? REM sleep seems to serve a different purpose than does NREM, or deep sleep.
After a very physically demanding day, people tend to spend more time in NREM deep
sleep than is usual. But an emotionally stressful day leads to increased time in REM sleep

sleep paralysis

the inability of the voluntary muscles

to move during REM sleep.

11p 12a 1a 2a 3a 4a 5a 6a 7a

Brief

awakenings

Longest periods

of deep sleep

Awake, alert: Beta Waves

Sleep Stage N1: Theta Waves

Sleep Stage N2: Spindles (bursts of activity)

Sleep spindle

Sleep Stage N3: Deep non-REM

Sleep Stage R

Bursts of synchronous

vertical eye movements

Low voltage continuous

theta with minimal beta

Awake, relaxed: Alpha Waves

N3

N2

N1

REM

Awake

Sleep Stages

Figure 4.3 Brain Activity During Sleep
The EEG reflects brain activity during both waking and sleep. This activity varies according to level of alertness while awake (top two segments) and the stage
of sleep. Stage N3 of sleep is characterized by the presence of delta activity, which is much slower and accounts for the larger, slower waves on these graphs.
R sleep has activity that resembles alert wakefulness but has relatively no muscle activity except rapid eye movement. The graph shows the typical progres-
sion through the night of Stages N1–N3 and R. The R sleep periods occur about every 90 minutes throughout the night (based on Dement, 1974). EEG data
and images in this figure are courtesy of Dr. Leslie Sherlin.

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