Dreaming - An Introduction to the Science of Sleep

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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...

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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 OXFORD UNIVERSITY PRESS
OXFORD U N I V E R S I T Y PRESS Great Clarendon Street, O x f o r d 0X2 6DP O x f o r d University Press is a department of the University of O x f o r d . It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide in Oxford New York Auckland Bangkok Buenos Aires Cape Town Chennai Dar es Salaam Delhi Hong Kong Istanbul Karachi Kolkata Kuala Lumpur Madrid Melbourne Mexico City Mumbai Nairobi Sao Paulo Shanghai Singapore Taipei Tokyo Toronto Oxford is a registered trade mark of O x f o r d University Press in the UK and in certain other countries Published in the United States by Oxford University Press Inc., N e w York © J. Allan Hobson 2 0 0 2 The moral rights of the author have been asserted Database right Oxford University Press (maker) First published in hardback 2 0 0 2 First published in paperback 2 0 0 3 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without the prior permission in writing of O x f o r d University Press, or as expressly permitted by law, or under t e r m s agreed with the appropriate reprographics rights organizations. Enquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, at the address above You must not circulate this book in any other binding or cover and you must impose this same condition on any acquirer British Library Cataloguing in Publication Data Data available Library of Congress Cataloging in Publication Data Data available ISBN 0 - - 1 9 - 2 8 0 4 8 2 - 0 1 3 5 7 9 1 0 8 6 4 2 Typeset by RefineCatch Ltd, Bungay, Suffolk Printed in Great Britain T.J. International L t d . , Padstow, Cornwall
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