The Nocturnal Brain

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  For Christian, it is not just dreams of his childhood friends; his recollection of his dreams is staggering. I am lucky if I remember a dream every couple of weeks. I find that on waking I can clearly recall details of the dream, but over a few minutes, these intense memories dissipate like wisps of mist in a breeze. For Christian, the details live with him, as bright and colourful as his daytime experiences. ‘There’s always something special about my hands in my dreams. I can always shoot lasers out of my hands. I can describe exactly how it happens in every dream. It’s always the same. I feel a pressure in my brain. I well up this ball of energy. I can feel it in my brain and I can feel this ball of energy getting bigger and bigger in my hand because I’m creating that ball of energy. Then I just fling it at people. I’m chucking balls of energy.’ I tell him it all sounds very Harry Potter, which triggers off other memories in him.

  ‘I walk through walls in my dreams, but when I walk through the wall it’s difficult to get my head through.’ He pauses, and thinks for a few seconds. ‘I wonder if there’s something going on in reality in my brain. I don’t know if the brain swells a little bit. I don’t know the science of that, but possibly in reality something’s happening while I’m asleep? It’s being transferred into my dream and I can’t get my head through the wall?’

  I suspect that he is describing the phenomenon of sensory information being integrated into dreams, as we discussed in Chapter 3, where perhaps abnormal movements of the limbs generate the violent dreams characteristic of REM sleep behaviour disorder. ‘Imagine if I had a spot, say, growing on my leg, but I didn’t know it was there, I didn’t notice it. That particular night I will almost certainly dream that there’s something there, but in my dream it will be something like a mushroom growing out of my leg.’

  Christian’s dreams are not all sweetness and light, love affairs and superpowers, however. Some of his dreams are deeply unpleasant. ‘A regular one is nuclear war. Always vivid. Horrible really. I’ve never been in a nuclear war obviously, I’m only going by video games, films, documentaries, that sort of thing.’ He goes on to describe his regular experience of a nuclear holocaust at night, dreams, or rather nightmares, filled with horror, death and destruction. ‘If, for example, we’re in the dream now, right this second, I’ll be sitting here talking to you and then the big mushroom cloud will go off, say, over in the distance. We start to panic or whatever. I can see the bombs coming down and I know where they’re going to land. And the bombs never go off immediately. We’ll leave the building trying to get to shelter somewhere. I’ve got to get underground somewhere. And then a bomb will go off right next to us. In reality you’d be vaporised in milliseconds, but in my dream, I have time to run away. Generally I don’t die; I’m always trying to save people.’

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  Christian’s regular recollection of his dreams is obviously a function of his unstable REM sleep, caused by his narcolepsy. As he shifts almost seamlessly between wake and REM and back again, his dreams regularly enter into his consciousness. The sheer intensity and quality of his dreams makes him wonder if there is some purpose to them, whether they are telling him something. But do they? Do dreams tell us something about us, our experiences, our desires, our personalities?

  The science of dreaming has undoubtedly been hindered by the historical rift between mind and body (in this sense, ‘body’ includes the physical brain). The concept of Cartesian dualism defines the body and soul to be entirely separate, and this view has influenced the schism between neurology, the medicine of the nervous system, from psychiatry, the medicine of the mind. In the past few decades, this artificial division has been slowly whittled away, and few neurologists or psychiatrists today would consider this view correct. We neurologists are very familiar with brain tumours or autoimmune brain disorders causing frank psychotic symptoms such as hallucinations or delusions, or even more subtle ‘psychiatric’ symptoms, such as anxiety or depression. Equally, looking through the current psychiatric journals, they are filled with research correlating conditions like schizophrenia or bipolar disorder with genetic variants, changes in neurotransmitters and altered activity in various parts of the brain.

  So it seems that the separation of mind and body, the mental and the physical, is slowly dying. In the world of dreams, however, all roads lead to Sigmund Freud. Freud’s theories regarding the origins of dreams are familiar to almost everyone. The concept that our dreams represent unfulfilled wishes or desires is the central tenet of Freudian theory. But the overt meaning of our dreams represents a censored version of suppressed emotions or desires, requiring interpretation. Our unconscious desires are repressed, from others but also ourselves, and our dreams are covert manifestations of these hidden wants. Rather than needing the Egyptian Dream Book to translate our dream content into predictions of the future, we need a psychoanalyst to tell us what they mean with regard to the dark depths of our mind. In some respects, Freud was a bridge between the two sides of Cartesian dualism. A neurologist by training, he quickly moved into the realm of psychiatry and developed his famous theories of psychoanalysis. Despite being in the era before the EEG and brain imaging, and not even knowing about REM sleep, he firmly placed dreaming in the physical world, originating from the brain. But his theories on dream interpretation were untestable, unprovable, and definitely had a flavour of the soul about them. Our inner spirits being tortured by our latent dark desires on a nightly basis, a manifestation of our Oedipal complex, or repressed sexual scenarios of childhood.

  Obviously, we can now clearly demonstrate that dreams originate in the brain. It is not only that dreams demonstrably arise in a measurable electrical brain state – REM sleep. From functional imaging studies, techniques that allow us to peer into the brain and understand the activity of various areas within it at certain points in time, we know that during REM sleep, various parts of our brains are extremely active. Simply thinking about your own dreams might allow you to predict which areas these might be. The hottest areas are those involved with emotion, movement, vision and autobiographical memory – the limbic system, motor cortex, visuospatial areas and hippocampus respectively. And, equally unsurprisingly, the major area that is quietened by REM sleep is the prefrontal cortex, the region of the brain responsible for rational thought and complex planning.

  But could it be that dreams are just an ‘epiphenomenon’ of REM sleep? Are the mental processes of dreaming simply a result of the random activation of these areas of the brain in REM sleep? Consider the simple act of taking a breath and exhaling. As you do so on a cold day, the steam of your exhalation is testament to the water that we lose with every breath. For an average-sized man, some 400 ml of water is lost in this way every day. But getting rid of water is obviously not the function of respiration. The water loss is simply a consequence of air passing over our moist airways, a by-product of the need to inhale oxygen and exhale carbon dioxide – an epiphenomenon. So, is dreaming similarly just a by-product of REM sleep, meaningless garbage that is simply a consequence of REM sleep performing some housekeeping role in the brain? On a personal level, it is hard to reconcile this view with our own experiences of sleep – dreams in which we see people we know, interact with realistic worlds, experience strong emotions. Even trying to be as dispassionate and scientific as I can, I find it difficult to understand how our dreams could represent the irrelevant dregs of an electrical process that has an entirely separate and unrelated purpose. And when I look at some of my patients, it is equally hard to comprehend.

  I think of a young man I saw recently, a refugee from the island of Sri Lanka. Born into a Tamil family, his early life was torn apart by the civil war, with intermittent periods of arrest, harassment and exposure to violence. Despite leaving Sri Lanka as a teenager, he is plagued by vivid nightmares every night or two, waking up screaming after the intense replaying of his traumatic experiences, even fifteen years later. These nightmares are a common feature of post-traumatic stress disorder (PTSD),
associated with daytime flashbacks and abnormal responses to reminders of experienced trauma. So, how could these recurrent nightmares, clearly linked to daytime experiences, simply be an epiphenomenon? It seems rather unlikely.

  In fact, one of the proposed functions of dreaming in REM sleep is what Matthew Walker terms ‘overnight therapy’. In wakefulness, our brains are flooded with various neurotransmitters, but as we enter sleep, this changes. In non-REM sleep, levels of acetylcholine, serotonin and noradrenaline (norepinephrine) fall away. But, as we enter into REM sleep, this once again changes. Noradrenaline levels in particular fall to their lowest, but acetylcholine is boosted to higher levels than seen in wakefulness. So, on a chemical level, the brain in REM sleep is active, but without noradrenaline, which, like its related hormone adrenaline, is fundamental to the ‘fright-fight-flight’ response. This chemical may also have a role in intensifying memories associated with strong emotions; if you look back on your life, your strongest memories are almost always those experiences associated with extreme joy, fear or excitement, and this is certainly the case for people with PTSD. However, elegant research has suggested that REM sleep may provide a mechanism to consolidate these memories, to uncouple them from their emotional context – in other words, to lessen the intensity of emotion associated with your experiences. Think of it from an evolutionary perspective: if your abiding memory of being bitten by a snake is the fear and pain, then the next time you see a snake you may simply freeze with fear, like some people with PTSD do when something reminds them of their traumatic experiences. It is important to remember that snakes bite – and the pain and fear of being bitten certainly helps – but also to be able to maintain rational thinking the next time you see one.

  So, perhaps REM is some form of psychological therapy, allowing us to rid ourselves of the emotional burden of some of our experiences. And maybe that explains why people with PTSD experience these recurrent nightmares. The traumatic experiences have generated such strong emotions, and the levels of noradrenaline are not fully suppressed, that these dreams or nightmares result in full awakenings. Each time the nightmare occurs, it is never completed, the emotions associated with that memory are not dampened down. Like a scratched record, the needle jumps out of the groove at the same point, and the song is never completed. The brain tries again and again and again to cleanse your memories of the fear, of the emotional trauma associated with them. In fact, a widely used drug in nightmares associated with PTSD, prazosin, acts mainly as a blocker of noradrenaline in the brain. Although a recent study suggests prazosin is no more effective than a placebo, I and my colleagues have seen several patients successfully treated with this drug.

  So, certainly in some people, it is the dream content itself that has significance. It is not simply the random noise generated by our brains in REM sleep. And, indeed, dream analysis experiments confirm our own individual experiences – that dreams, while rarely rerunning the events of the day before, often have similar emotional themes, such as worries, anxieties or anger, as those experienced the previous day. Our daytime world colours our nocturnal lives. But is the precise content of our dreams important? Well, there is perhaps a little evidence to support this. Subjects who are given the task of navigating a maze in virtual reality performed much better if they reported dreams of moving through a complex environment than those who had other types of dreams, although crucially these were not the dreams of REM sleep.

  Perhaps the hypothesis that attracts me most is the theory of REM sleep and dreaming proposed by Hobson and his collaborator Karl Friston, a serious heavyweight of the neuroscience world. I am not sure why this theory entices me so much. It may be that it shares parallels with the first paper that I read on sleep as an ignorant but interested medical student, described in the introduction to this book, by Crick and Mitchison. They argued that REM sleep was the process of reverse learning, cleansing the neural networks of unnecessary connections formed through our experiences during the day, and that dreaming represented the rubbish being taken out. Hobson and Friston’s hypothesis is somewhat different, and another of its attractions is that it really unifies the worlds of REM sleep and dreaming, and in some respects the body and mind. It explains a purpose to our dreams. The theory is somewhat complex, and despite reading the papers repeatedly I am not entirely convinced afterwards that I fully understand it. This is the real reason I call Hobson on the telephone; I am seeking an idiot’s guide to their theory. When I tell him I am not sure I totally understand it, he jokes: ‘Neither do I!’ But he does go on to provide an explanation.

  Essentially, how we understand the world around us is based upon the interpretation of vision, feeling, sound, movement and experience. In order to do this, our brains, complex machines that take these inputs and ascribe meaning to them, need to have a model of the world around us. To some extent, that model, that basic circuitry, is genetically endowed. We are born with it. Indeed, it is present before we are born. Hobson tells me, ‘The brain doesn’t simply respond to external stimuli; the brain has a strong set of expectations. And you can say those are learned, but what Friston and I are saying is that they are learned before learning, they are genetically programmed.’ But that model needs to be tweaked, constantly adjusted, and develops through life to define who we are as individuals. It determines whether we like wine, if we prefer Dali or Constable, or how we respond to our partners when we have an argument. Hobson continues: ‘The job of the brain is to anticipate reality, and it can’t do that passively; it does that actively. It has a set of assumptions which then adjusts according to data. You and I have different ways of thinking because we are different people. And we have had different experiences. Our brains are probably not all that different, but the models that we have of the world are quite different.’

  Essentially, this model defines our consciousness, but the tweaking can only happen when we are offline, detached from the external world, unable to move, rendered asunder from the world around us, even cut off from the processes through which we regulate our temperature. During REM sleep, Hobson and Friston believe that the brain integrates our experiences into this model, refining and moulding it, and our dreams represent a virtual reality environment in which this takes place. Ultimately, our dreams represent an amalgam of our experiences, our own cumulative model of the world rehearsed in a million different ways, all in the pursuit of understanding our own personal world and determining our individual consciousness. ‘Your dreams are the subjective experience of the running of that model and that’s what ties our work to psychoanalysis. The interpretation of dreams could be thought of as a way of understanding the model that the person has of the world. And the model that the person has of the world is clearly a function – in part – of his experience,’ Hobson tells me.

  In a way, this theory is also inclusive of Freud’s view that our dreams are linked to childhood experiences, although Hobson implies Freud’s mistake was to make it all about sex. ‘I think what the Freudians have done is to sexualise something that is only part sexual and a very large part something else.’ He has been keeping a dream diary for decades now. ‘My sexual dreams are about 5 per cent of my dreams, by the way. If you think that all the other 95 per cent are governed by my Oedipal wishes, that seems to me absurd.’

  I think that Christian’s dreams of his youth represent something about his views of his childhood. He later tells me that his friends comment that there is an air of sadness about him, a tendency to hark back to younger, happier days, a loss of that contentment in earlier years. Rather than illustrating unvoiced sexual desires, both he and I believe that these dreams represent a wish to be back in those simpler years, unaffected by the challenges of adulthood and his narcolepsy.

  And so it makes sense that some of our dreams may reflect the experiences of the day before, while others may bear no such meaningful relationship. They are the summation of our life to date. It is also unsurprising, therefore, that some dreams or nightmares may recur, in an effort t
o understand the meaning of our daytime experiences. But these dreams are a function of the brain. ‘The brain creates the mind and the mind creates the brain,’ Hobson says. The brain and the mind are one and the same. Cartesian dualism is dead.

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  Christian also describes prominent lucid dreaming, like Evelyn in Chapter 9. He has some degree of consciousness or awareness of his dreams, and can to some extent influence them. I think he rather enjoys it. He feels he has established control over his hypnagogic hallucinations, the succubus that previously visited him every night – ‘over time I have battled it, and made it go away’ – but now he can also direct his night-time life too. ‘I can really easily lucid-dream,’ he tells me. ‘I can give you a really good example. I’ve never been to Hong Kong, I’m only going by films or video games that I’ve played or seen. In the dream I was in my version of Hong Kong – narrow backstreets, with all the big adverts for Coca-Cola – and I remember walking around those streets. I was staying at a hotel and I could literally walk around the hotel and go to the bar. I remember I went to the bar of my own accord.’ I ask him if he genuinely felt that he was in control. ‘There are many aspects of that dream that I wasn’t in control of, because the nature of dreams is quite fantastical. But yes, I was able to walk around, communicate with people. I went to the bar, then walked out of the hotel. I remember going into a shop to look at clothing on a clothes rail. And then just kind of picking through this clothing. But I was actually in the dream, controlling it like it was reality.’