Dreaming - An Introduction to the Science of Sleep
Dreaming has fascinated humankind since the dawn of
recorded history. As dreaming is so vivid, so complex,
and so emotional , it has inspired religious movements ,
artistic representations, and introspective scientific theories. All
of these pre-modern expressions have been based on the idea
that dreams contain messages that cannot be delivered in any
other way.
Thus, i t was thought by the early Judaeo-Christians that God
communicated his intentions via certain prophets to his human
subjects. This concept was the centrepiece of medieval dream
theory with its postulates of the 'Gates of Horn and Ivory' .
Religious reformers such...
Dreaming
An Introduction to the Science of Sleep
J . A l l a n H o b s o n i s Professor o f Psychiatry a t Harvard Medical
School, Boston, Massachusetts. He was the recipient of the
Distinguished Scientist Award of the Sleep R e s e a r c h Society
in 1 9 8 8 .
His major research interests are the neurophysiological basis of
the mind and behaviour; sleep and dreaming; and the history of
neurology and psychiatry, with his m o s t r e c e n t w o r k focussing
on the cognitive features and benefits of sleep. He is the author
or co-author of many b o o k s , including: The Dreaming Brain
( 1 9 8 8 ) , Sleep ( 1 9 9 5 ) , Consciousness ( 1 9 9 9 ) , Dreaming as Delirium:
How the brain goes out of its mind ( 1 9 9 9 ) , The Dream Drugstore
( 2 0 0 1 ) , and Out of its Mind: Psychiatry in Crisis ( 2 0 0 1 ) .
Dreaming
An Introduction to the Science of Sleep
J. ALLAN HOBSON, MD
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T h e research upon which this b o o k is based was c o n d u c t e d in the
author's laboratory at the Massachusetts Mental Health C e n t r e
when it was supported by grants for the N I H , N S F , N I D A , and
the John T. and Catherine D. M a c A r t h u r Foundation. I thank my
colleagues for their collaboration and Nicholas Tranquillo for
help with the manuscript.
v
Introduction xi
1 What is dreaming? 1
2 Why did the analysis of dream content fail to become a
science? 17
3 How is the brain activated in sleep? 35
4 Cells and molecules of the dreaming brain 53
5 Why dream? The functions of brain activation in sleep 71
6 Disorders of dreaming 88
7 Dreaming as delirium: sleep and mental illness 97
8 The new neuropsychology of dreaming 106
9 Dreaming, learning, and memory 119
10 Dream consciousness 133
11 The interpretation of dreams 147
Conclusion 158
Index 161
vii
1 Does everyone dream? 11
2 Can dreams foretell the future? 20
3 Do we dream in black and white or in colour? 43
4 Do animals dream? 57
5 When does dreaming start? 73
6 Do blind people see in their dreams? 116
7 Are dreams caused by indigestion? 126
8 What is lucid dreaming? 140
9 Are men's and women's dreams different? 151—2
viii
1 The Nightcap 14
2 Behavioural states in humans 41
3 The visual brain during REM sleep 60
4 Schematic representation of REM sleep 65
5 How sleep patterns change over our lifetime 77
6 Variation in sleep length 79
7 Autonomic activation in sleep 90
8 Sleep changes in depression 105
9 Data from positron emission tomography (PET) 111
10 Visual discrimination task learning and sleep 125
11 The human brain 135
ix
1 Two models that offer different explanations of the altered
state of dreaming 18
2 The psychological basis for the differences between waking
and sleeping 26
3 Imaging of brain activation in R E M sleep and the effects of
brain damage on dreaming 109
4 Areas of the brain dealing with the different components
of consciousness 134
5 Alterations of consciousness in dreaming 143
X
D
reaming has fascinated humankind since the dawn of
r e c o r d e d history. As dreaming is so vivid, so c o m p l e x ,
and so e m o t i o n a l , it has inspired religious m o v e m e n t s ,
artistic representations, and introspective scientific theories. All
of these p r e - m o d e r n expressions have b e e n based on the idea
that dreams contain messages that cannot be delivered in any
other way.
Thus, it was thought by the early Judaeo-Christians that G o d
communicated his intentions via certain prophets to his human
subjects. This c o n c e p t was the c e n t r e p i e c e of medieval dream
theory with its postulates of the ' G a t e s of H o r n and I v o r y ' .
Religious r e f o r m e r s such as E m m a n u e l Swedenburg w e r e able to
m e e t G o d ' s angels in dreams and he thereby received instruc-
tions about founding the C h u r c h of the N e w J e r u s a l e m .
Early W e s t e r n artists, such as G i o t t o , used dreaming as a
vehicle for the pictorial representation of prophetic inspiration.
Sleeping saints and c h u r c h m e n are shown in the same pictorial
frame as the visions that their dreams inspired. In m o d e r n art,
the surrealists expressed through their wild paintings the convic-
tion that dreaming was a m o r e authentic state of consciousness
than waking. Salvador Dali, M a x E r n s t , and R e n e M a g r i t t e all
painted in dream language. Dali was the m o s t surreal, E r n s t the
most psychoanalytic, and M a g r i t t e the m o s t neuropsychological
of these artists.
xi
Introduction
At the turn of the twentieth c e n t u r y , the best known of all
dream investigators would be Sigmund Freud, w h o set out to
base his t h e o r y of the mind on brain s c i e n c e . His knowledge of
the brain was so i n c o m p l e t e that he was forced to abandon his
famous ' P r o j e c t for a Scientific P s y c h o l o g y ' , and he turned to
dreaming for insights about what he construed to be the dynamic
unconscious. He decided, as had all his symbolist predecessors,
that dreams c o n c e a l e d hidden meanings elaborated as one part of
the m i n d , and that the unconscious tried to break through the
protective b a r r i e r of consciousness. Freud thus threw dream
t h e o r y b a c k to the t i m e of Biblical scholars, A r t e m i d o r u s , and
o t h e r early i n t e r p r e t e r s o f dreams.
This b o o k takes up w h e r e Freud left off when he abandoned
his P r o j e c t . It tries to build a n e w dream theory on the now solid
and extensive base of sleep s c i e n c e . To accomplish this goal, I
have given a c o n c i s e summary of the findings of basic brain
r e s e a r c h , sleep lab studies, and r e c e n t clinical studies of sleep
and dreams. T h r o u g h o u t the b o o k , I use examples taken from my
own dream j o u r n a l t o illustrate h o w our n e w theory o f dreams,
called activation—synthesis, can be used to explain in physio-
logical t e r m s universal dream features previously ascribed to
psychodynamic factors. O n c e this is done, the mystery of dream-
ing is largely stripped away, leaving the c o n t e n t nakedly open to
understanding w i t h o u t c o m p l e x interpretation.
T h e main goal of this b o o k is to show how a scientific theory
of dreaming has b e e n developed and strengthened over the past
SO years. In the process, the b o o k offers the reader a unique
opportunity to r e c o n s i d e r his or her own dream theory and, into
the bargain, to learn about the fascinating discoveries of m o d e r n
sleep s c i e n c e .
xii
I
What is dreaming?
W
hat causes dreaming? W h y are dreams so strange?
W h y are they so hard to r e m e m b e r ? A t r u e s c i e n c e
of dreaming requires a reliable definition that can
lead to the reliable identification of this state and m e t h o d s of
measuring its properties. During the c o u r s e of w o r k on the
brain, which led to the suspicion that it might be brain activation
in sleep that causes dreaming, we realized that the m o s t scien-
tifically useful way to define and measure dreaming was to focus
on the formal features rather than the c o n t e n t — b y this is m e a n t
the perceptual (how we p e r c e i v e ) , cognitive (how we t h i n k ) , and
emotional (how we feel) qualities of dreaming, whatever the
details of the individual stories and scenarios might b e .
T h e radical change in emphasis, from the analysis of c o n t e n t
to the analysis of f o r m , exemplifies what scientists call a para-
digm shift (a rapid change in pattern or t h e o r y ) . T h r o u g h a
formal approach, we found an entirely n e w and different way of
looking at a familiar p h e n o m e n o n . W h e r e a s previously students
i
What is dreaming?
of dreaming had invariably asked ' W h a t does the dream m e a n ? ' ,
we asked what the m e n t a l characteristics of dreaming are that
distinguish it from waking mental activity. We are not saying that
dream content is unimportant, uninformative, or even
uninterpretable. Indeed, we believe that dreaming is all three of
these things, but it is already crystal clear that many aspects of
dreaming previously thought to be meaningful, privileged, and
interpretable psychologically are the simple reflection of the
sleep-related changes in brain state that we start to detail in
Chapter 3.
To provide a firmer grasp of the distinction b e t w e e n form
and c o n t e n t , I offer an e x a m p l e , taken at r a n d o m from my own
d r e a m j o u r n a l , which is o n e of hundreds that I have recorded
over the years. To give a c o m p l e t e sense of how my journal reads
and to allow the reader to c o m p a r e his or h e r own notes on
dreaming with m i n e I q u o t e the entry in full. I k n o w that you will
dream of subjects quite different from m i n e , but I suspect that
the f o r m of your dreams is similar.
1 0 / 5 / 1 9 8 7 En route to New Orleans for a debate on dreams at the Ameri-
can Psychiatric Association's annual meeting: Two nights ago, a
dream of Richard Newland
It is a house maintenance nightmare. I have too much property to
maintain. Richard and a friend are 'helping' me but it is an uncertain
alliance, with the twin threats of incompetence and inattentiveness.
There are several scenes all with the same emotional theme: anxiety
about maintenance details.
In one scene we are walking along in hilly country, perhaps toward
the house, but the destination is not clear.
Then we are in a house, not at all like mine but assumed by my
dreaming brain to be mine, and Richard's friend is spray painting the
white wall (we have none in our house) with blue paint (neither do we
2
What is dreaming?
have any blue rooms). The paint sprayer is a tank device of the type used
to apply copper sulphate to grapevines or to exterminate cockroaches.
Suddenly, the paint is being sprayed not only on the wall but upon a
painting hanging on the wall.
My fears are confirmed. I yell at Richard to bid his friend stop.
For some reason, he has to go upstairs to turn off the machine
(although it appears to be fully portable and self-contained) and this
takes an inordinate length of time as the painting continues to suffer.
There follows a long dialogue with Richard who, while retaining
continuous identity as Richard, changes physiognomy repeatedly. His
face changed as follows: a gnome-like Napoleon Carter with a cherubic
sun-burned face; a wry smile and a Chinese coolie-type hat; a calf face—
as in A Midsummer Night's D r e a m (the ad for which did not include
the calf!);and as far as I can tell, never included Richard!
I can't remember other faces or other action from this long episode.
Before discussing the distinctions of f o r m against c o n t e n t
that this dream so clearly illustrates, I should c o m m e n t on the
3
W h a t is dreaming?
circumstances of its recording and the timing of its o c c u r r e n c e . I
was on an aeroplane, w h e r e I do a great deal of my journal
writing. I was flying to N e w Orleans for a highly publicized and
well-attended public debate on dreaming. I usually record
dreams on the m o r n i n g after their o c c u r r e n c e . T h e fact that I
waited t w o days in this case probably resulted in loss of detail.
But, as I will presently show, there is m o r e than enough detail to
m a k e clear the distinction b e t w e e n dream form and dream
content.
As far as the content is c o n c e r n e d , the dream is about my
c o n c e r n s for the upkeep of my farm in n o r t h e r n V e r m o n t , which
I have owned since 1 9 6 5 . R i c h a r d Newland is the son of my
f a r m e r neighbour, Marshall Newland, with w h o m I have had a
long and c o m p l i c a t e d but successful and gratifying relationship.
In spite of widely divergent priorities we have managed to get
along and to help each other.
F o r m e , the meaning of the dream is transparent: I am
anxious about my p r o p e r t y and about entrusting it to people
w h o are careless about their own houses. This characteristic,
k n o w n in psychological t e r m s as emotional salience ( o r rele-
v a n c e ) , is all I n e e d to understand the dream, which is a variant
on the t h e m e of i n c o m p l e t e arrangements that is so recurrent
in my dreams and in those of m o s t of my friends. For reasons
that I discuss m o r e fully in Chapter 2, I see no need and no
justification for treating this dream as a disguised, symbolic
expression of anxiety about o t h e r related themes (my wife's
interest in another V e r m o n t neighbour, for e x a m p l e ) . W h i l e
admitting that it could be appropriate and m o r e useful to notice
such an association, it does n o t help in understanding what
caused this d r e a m , d e t e r m i n e d its c o m i c a l bizarreness, and made
it so hard to r e m e m b e r .
4
W h a t is dreaming?
Form as opposed to content
To answer the questions about causes and characteristics of
dreams, it is helpful to take a formal analytical approach.
As is typical of most dreams, I am so involved in the scenario
that it never occurs to me that I am dreaming. As I see R i c h a r d
Newland (and his unidentified friend), see my house (even
though it is clearly n o t m i n e ) , see the blue paint as it is sprayed on
the walls, and move through the sequence of scenes, I a c c e p t all
of these unlikely features as real on the strength of my hallucin-
atory perceptions, my delusional beliefs about t h e m , and my
very strong feelings of anxiety and apprehension.
W h a t this means is that our sense of psychological r e a l i t y —
whether n o r m a l dreaming or a psychotic s y m p t o m — i s set by
the strength of percepts and feelings as well as by our thoughts
about t h e m . Internally generated p e r c e p t i o n s and e m o t i o n s are
two formal features of dreams and they are cardinal features. To
explain their intensity ( c o m p a r e d with w a k i n g ) , we might
e x p e c t to find that parts of the brain that generate e m o t i o n s and
related percepts are selectively activated in sleep. We see in
Chapter S that this is precisely what happens!
My Richard Newland dream is n o t simply perceptually vivid
and emotionally salient, it is also cognitively bizarre, by w h i c h I
mean that, despite the persistence of the main t h e m e s , t h e r e is a
flagrant disregard for the constancies of t i m e , place, and p e r s o n .
Notice that Richard's friend is n o t identified; n o t i c e also that the
house that is supposed to be m i n e could n o t possibly be so; and
notice that the scenes—however poorly recalled and
d e s c r i b e d — m e l d into one another: first we are outside walking,
then inside painting. N o t i c e , m o s t of all, that R i c h a r d ' s face
assumes a series of non-Richard features without ever
5
What is dreaming?
challenging either the assumption that he is Richard, or that I am
n o t awake but dreaming, as even a g l i m m e r of self-reflective
awareness would declare m e t o b e .
T h e s e are the cardinal cognitive features of dreaming: loss of
awareness of self (self-reflective awareness); loss of orientational
stability; loss of directed thought; reduction in logical reasoning;
and, last but n o t least, p o o r m e m o r y both within and after the
d r e a m . T h e fact that the incongruities and discontinuities of my
Richard Newland dream are c o n n e c t e d by association does not
explain the looseness of those associations. T h u s , it is true that
the unusual spray-painting device resembles an agricultural tool;
it is also true that R i c h a r d ' s transformed face is, first, that of
another Vermont farmer neighbour, Napoleon Carter, and
later a c a l f (Richard and his dairy farmer father, Marshall, had
many calves); and it is remarkably true that Shakespeare himself
celebrated the transformation of c h a r a c t e r s — t u r n i n g them into
each o t h e r and even into animals—in A Midsummer Night's Dream.
W h a t causes the processing of such e x t r e m e associations
(hyperassociative processing)? Freud, like his followers,
religiously believed that dream bizarreness was a psychological
defence against an unacceptable unconscious wish. This seemed
unlikely to many people in 1 9 0 0 . At the beginning of the twenty-
first c e n t u r y , it s e e m s impossible to us.
J u s t as we e x p e c t (and find) selective activation of brain
circuits underlying e m o t i o n and related percepts in rapid eye
m o v e m e n t ( R E M ) sleep, so we seek (and find) selective inacti-
vation o f brain c i r c u i t s — a n d chemicals—underlying m e m o r y ,
directed thought, self-reflective awareness, and logical
reasoning.
You may be m o r e or less pleased by the story. You might
prefer to believe that your dreams are secret messages of
6
