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To make sense of neural static. Other researchers propose that dreams erupt from
neural activation spreading upward from the brainstem (Antrobus, 1991; Hobson, 2009).
According to the activation-synthesis theory, dreams are the brain’s attempt to synthesize
random neural activity. Much as a neurosurgeon can produce hallucinations by stimulat-
ing different parts of a patient’s cortex, so can stimulation originating within the brain. As
Freud might have expected, PET scans of sleeping people also reveal increased activity in
the emotion-related limbic system (in the amygdala) during emotional dreams (Schwartz,
2012). In contrast, the frontal lobe regions responsible for inhibition and logical thinking
seem to idle, which may explain why we are less inhibited when dreaming than when
awake (Maquet et al., 1996). Add the limbic system’s emotional tone to the brain’s visual
bursts and — voila! — we dream. Damage either the limbic system or the visual centers
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active during dreaming, and dreaming itself may be impaired (Domhoff, 2003).
To reflect cognitive development. Some dream researchers focus on dreams as part
of brain maturation and cognitive development (Domhoff, 2010, 2011; Foulkes, 1999). For
Copyright © Bedford, Freeman & Worth Publishers.
example, prior to age 9, children’s dreams seem more like a slide show and less like an active
story in which the dreamer is an actor. Dreams overlap with waking cognition and feature
coherent speech. They simulate reality by drawing on our concepts and knowledge. They
engage brain networks that also are active during daydreaming — and so may be viewed as
intensified mind-wandering, enhanced by visual imagery (Fox et al., 2013). Unlike the idea
that dreams arise from bottom-up brain activation, the cognitive perspective emphasizes our
mind’s top-down control of our dream content (Nir & Tononi, 2010). Dreams, says Domhoff
(2014), “dramatize our wishes, fears, concerns, and interests in striking scenarios that we
experience as real events.”
Table 1.5-4 compares these major dream theories. Although today’s sleep researchers
debate dreams’ functions — and some are skeptical that dreams serve any function — they
do agree on one thing: We need REM sleep. Deprived of it by repeated awakenings, people
return more and more quickly to the REM stage after falling back to sleep. When finally
allowed to sleep undisturbed, they literally sleep like babies — with increased REM sleep, a
phenomenon called REM rebound. Most other mammals also experience REM rebound,
REM rebound the tendency for
REM sleep to increase following suggesting that the causes and functions of REM sleep are deeply biological. (That REM
REM sleep deprivation. sleep occurs in mammals — and not in animals such as fish, whose behavior is less influ-
enced by learning — fits the information-processing, or consolidation, theory of dreams.)

TABLE 1.5-4 Dream Theories

Theory Explanation Critical Considerations

Information processing/ Dreams help us sort out the day’s events and But why do we sometimes dream about
consolidation consolidate our memories. things we have not experienced and about
past events?
Physiological function Regular brain stimulation from REM sleep may help This does not explain why we experience
develop and preserve neural pathways. meaningful dreams.
Activation synthesis REM sleep triggers neural activity that evokes random The individual’s brain is weaving the stories,
visual memories, which our sleeping brain weaves into which still tells us something about the
stories. dreamer.
Cognitive development Dream content reflects dreamers’ level of cognitive Does not propose an adaptive function of
development — their knowledge and understanding. dreams.
Dreams simulate our lives, including worst-case
scenarios.

112 Unit 1 Biological Bases of Behavior

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