Dreams and Dreaming

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Chapter 4 Consciousness
REM sleep may also be a time for creating and strengthening connections between
nerve cells in the brain (Graves, Pack, & Abel, 2001; Maquet, 2001; Peigneux et al.,
2001). If so, it would explain why infants and children—whose brains are still developing—spend so much time in REM. Evidence favoring this possibility comes from
animal research showing that REM sleep helps in the creation of neural connections
following new learning experiences (Frank et al., 2001). There is also evidence that REM
sleep deprivation slows the creation of these connections (Kim, Mahmoud, & Grover,
2005). So REM sleep may help to solidify and absorb the day’s experiences and skills
(Fischer et al., 2002; Sejnowski & Destexhe, 2000; Stickgold, James, & Hobson, 2000).
In one study, people who were REM deprived showed poorer performance at a skill
they had learned the day before when compared with people who were either deprived
of non-REM sleep or had slept normally (Karni et al., 1994). Another study found that
establishing memories of emotional information was particularly dependent on REM
sleep (Wagner, Gais, & Born, 2001). Even 60- to 90-minute naps in which REM sleep
appears can be enough to solidify the learning of visual information (Mednick,
Nakayama, & Stickgold, 2003).
Dreams and Dreaming
dreams Story-like sequences of images, sensations, and perceptions that
last from several seconds to many minutes and occur mainly during REM
sleep.
lucid dreaming Being aware that a
dream is a dream while it is occurring.
We have seen that the brain is active in all sleep stages (for a summary of our discussion, see “In Review: Sleep and Sleep Disorders”). Some of this brain activity during
sleep is experienced as the story-like sensations and perceptions known as dreams.
Dreams may be as short as a few seconds or last for many minutes. They may be organized or chaotic, realistic or fantastic, peaceful or exciting (Hobson & Stickgold, 1994).
Some dreaming occurs during non-REM sleep, but most dreams—and the most
bizarre and vivid dreams—occur during REM (Casagrande et al., 1996; Dement &
Kleitman, 1957; Stickgold, Rittenhouse, & Hobson, 1994). Even when they seem to
make no sense, dreams may contain a certain amount of logic. For example, when people read dream reports whose segments had been randomly reordered, they could correctly say which had been rearranged and which were intact. And although dreams
often involve one person transforming into another or one object turning into another
object, it is rare that objects become people or vice versa (Stickgold et al., 1994).
Daytime activities may influence the content of dreams to some extent (Foulkes,
1985; Wegner, Wenzlaff, & Kozak, 2004). In one study, people wore red-tinted goggles
for a few minutes just before going to sleep. Although they didn’t know the purpose of
the study, the next morning they reported more red images in their dreams than people who had not worn the goggles (Roffwarg, Hermann, & Bowe-Anders, 1978). It is also
sometimes possible to intentionally direct dream content. This is called lucid dreaming, because the sleeper is aware of dreaming while a dream is occurring (Stickgold,
Malia, et al., 2000).
Research leaves little doubt that everyone dreams during every night of normal
sleep. Even blind people dream, although their perceptual experiences are usually not
visual. Whether you remember a dream depends on how you sleep and wake up. Recall
is better if you awaken abruptly and lie quietly while writing or tape-recording your
recollections.
Why do we dream? Theories abound (Antrobus, 2001; Domhoff, 2001; Eiser, 2005).
Some see dreaming as a process through which all species with complex brains analyze
and consolidate information that is personally important or has survival value (Payne
& Nadel, 2004; Porte & Hobson, 1996; Zadra, Desjardins, & Marcotte, 2006). This view
is supported by the fact that dreaming appears to occur in most mammals, as indicated
by the appearance of REM sleep. For example, after researchers disabled the neurons
that cause REM sleep paralysis, sleeping cats ran around and attacked, or seemed
alarmed by, unseen objects, presumably the images from dreams (Winson, 1990).
According to Freud (1900), dreams are a disguised form of wish fulfillment, a way
to satisfy unconscious urges or resolve unconscious conflicts that are too upsetting to
deal with consciously. For example, a person’s sexual desires might appear in a dream
as the rhythmic motions of a horseback ride. Conflicting feelings about a parent might
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in review
Sleeping and Dreaming
SLEEP AND SLEEP DISORDERS
Types of Sleep
Characteristics
Possible Functions
Slow wave
(stages 3 and 4)
The deepest stages of sleep, characterized
by slowed heart rate and breathing,
reduced blood pressure, and low-frequency,
high-amplitude brain waves
Refreshing of body and brain; memory
consolidation
Rapid eye movement (REM)
sleep
Characterized by eye movements, waking
levels of heart rate, breathing, blood
pressure, and brain waves, but nearparalysis in muscles
Restoring sensitivity to norepinephrine,
thus improving waking alertness; creating
and solidifying nerve cell connections;
consolidating memories and new skills
Sleep Disorders
Characteristics
Possible Causes
Insomnia
Difficulty (lasting at least a month) in
falling asleep or staying asleep
Worry, anxiety
Narcolepsy
Sudden switching from a waking state to
REM sleep
Absence or deficiency in orexin
(hypocretin)
Sleep apnea
Frequent episodes of interrupted
breathing while asleep
Genetic predisposition, obesity, faulty
breathing-related brain mechanisms,
windpipe compression
Sudden infant death
syndrome (SIDS)
Interruption of an infant’s breathing,
resulting in death
Genetic predisposition, faulty breathingrelated brain mechanisms
Nightmares
Frightening dreams during REM sleep
Stressful or traumatic events or
experiences
Night terrors
Frightening dream images during nonREM sleep
Stressful or traumatic events or
experiences
REM behavior disorder
Lack of paralysis during REM sleep allows
dreams to be enacted, sometimes with
harmful consequences
Malfunction of brain mechanism
normally creating REM paralysis
?
1. Jet lag occurs because of a disruption in a traveler’s
.
2. The importance of non-REM sleep is suggested by its appearance
3. The safest sleeping position for babies is
.
in the night.
appear as a dream about a fight. Seeing his patients’ dreams as a “royal road to a knowledge of the unconscious,” Freud interpreted their meaning as part of his psychoanalytic therapy methods (see the chapter on the treatment of psychological disorders).
In contrast, the activation-synthesis theory describes dreams as the meaningless
byproducts of REM sleep (Hobson, 1997). According to this theory, hindbrain arousal
during REM creates random messages that activate the brain, especially the cerebral
cortex. Dreams result as the cortex connects, or synthesizes, these messages as best as it
can, using stored memories and current feelings to organize this random brain activity into something more coherent. From this perspective, dreams represent the brain’s
attempt to make sense of meaningless stimulation during sleep, much as we might try
to find meaningful shapes in cloud formations (Bernstein & Roberts, 1995; Rittenhouse,
Stickgold, & Hobson, 1994).
Even if dreams arise from random brain activity, their content may still have psychological significance. Some psychologists believe that dreams give people a chance to review
and address some of the problems they face during waking hours (Cartwright, 1993).