Dreams have been explained as divine revelations, as prophecies, as messages revealing that the dreamer’s soul has temporarily left his body to roam. According to the Azande of Central Africa, when a person has a bad dream, he is experiencing the efforts of a witch to devour the soul of his flesh.1 But dreams have also been the subject of extensive rational and scientific inquiry, and The Dreaming Brain is the most recent scientific attempt to explain an experience that has always attracted and yet defeated explanation.

Hobson, a professor of psychiatry at Harvard Medical School, begins his book by explaining he is taking “a brain-based approach to dreaming,” i.e., an approach that seeks to show how dreams result from states and processes within the brain. He goes on to give a summary of the work on dreaming by a number of thinkers and scientists in the nineteenth century—a century that was notable for research into dreams and an interest in them. Thus Hermann von Helmholtz, best known perhaps as the inventor of the ophthalmoscope, and the founder of perceptual physiology, suggested that the brain commands the body’s movements in sleep as well as in the waking state, and that these movements give rise to the images of dreams.

But, Hobson claims, the growing body of nineteenth-century research into the physiological and psychological origin of dreams was to a large extent displaced by Freud’s The Interpretation of Dreams, first published in 1900, which, in its exclusive reliance on personal reports, redirected the study of dream research. The Interpretation of Dreams was “anti-scientific,” Hobson alleges, because in it “Freud so forcefully dismissed all previous writers that he actually aborted an emerging experimental tradition.”

Scientific inquiry was in any case handicapped by lack of knowledge about the brain and of techniques for investigating it. Still, in the decades just after World War II, important advances were made. In investigating the brain stem (that is, the lower part of the brain connected to the spinal cord), researchers found that it contained a network of neurons, known as the reticular formation, in which increased electrical activity was correlated with both arousal from sleep and continued wakefulness. Then, in 1953, a breakthrough occurred. Eugene Aserinsky and Nathaniel Kleitman discovered that intermittent periods of rapid eye movement (REM) took place during sleep, and that these periods were closely associated with visual dreaming. The next step consisted of discoveries suggesting that these periods of REM sleep were connected with neural activity in an upper region of the brain stem, known as the pons.

Hobson presents a clear account of these developments in psychoneurology and neurophysiology. This is important because they provide the background to a major advance that later occurred in developing techniques of neuropsychological investigation, and in our knowledge of brain functions. During the 1950s and early 1960s, neurophysiologists and psychologists were able to record the electrical activity of a single neuron in the brain with a microelectrode, giving us what Hobson describes as “a window on the brain.” When several researchers, including David Hubel and Edward Evarts, used this window—along with established methods measuring EEG patterns, muscle potential, and eye movements—to examine the neuronal activity involved in sleep, in particular REM sleep, they found that visual and motor centers in the cortex of the brain became active during REM sleep. Hobson and a colleague then began to explore the pontine region in the upper part of the brain stem of cats “in search of neurons,” he tells us, “whose electrical activity might mediate the widespread cortical activation, the motor inhibition, and the rapid eye movements that gave REM its name.” They found that these features of REM periods are apparently produced by a specific subgroup of neurons in the pons, among which the “giant” cells in the reticular formation were particularly important.

All this, however, still left unresolved the problem of locating the precise mechanism that triggers REM sleep. Hobson and his co-workers suggested that the giant cells work by means of substances known as cholinergic neurotransmitters, which have an excitatory effect on neurons, whereas other cells in the brain stem work by means of substances known as aminergic neurotransmitters, and these have an inhibiting effect on neurons. Hobson and others found that the cholinergic and aminergic neurons behave inversely during REM sleep, the activity in the one being high when the activity in the other is low. Accordingly, he proposed what he calls a “reciprocal-interaction model of REM-sleep generation.” REM sleep comes about when the activity of the inhibitory aminergic neurons drops sufficiently to allow the excitatory cholinergic ones to escape from inhibitory control.

Hobson suggests that the “continuous competition between excitatory reticular cholinergic neurons and the inhibitory aminergic neurons,” when mediated by their neurotransmitters, forms the basic process involved in dreaming; and that REM sleep is governed by continuous cyclical activity, alternating between the two neuronal groups of the brain stem, in what he describes as “a war of nerves.”


This neuronal activity is a sort of continuous war whose effects spread from the brain stem throughout the brain [through networks of connections with the cholinergic and aminergic neurons], taking the mind hostage. This battle for the mind occurs regularly—and silently—every night in our sleep. And the only outward sign may be the fleeting recollection of a dream as we read the morning newspaper!

Hobson makes it clear that his model of reciprocal interaction is still only a hypothesis. Nevertheless, he claims in effect that it is sufficiently well supported to warrant being taken very seriously. The neuropsychological work outlined in Hobson’s book is most impressive and testifies to the remarkable accomplishments of many researchers in this difficult field. (The reader who wishes to have a fuller technical account of this work should consult the monograph by J.A. Hobson and M. Steriade in Handbook of Physiology: Vol. IV, The Nervous System, ed. V.B. Mountcastle, American Physiological Society, 1986.)


How does Hobson use these discoveries about sleep and brain function to explain dreams? He first outlines an “activation-synthesis” hypothesis, which he explains partly by contrasting it with what he regards as its chief competitor, Freud’s psychoanalytic account of dreams, which he rejects almost completely.

The activity in the brain stem, according to Hobson, is transmitted to the cerebral cortex in what amounts to a near-random barrage of nerve impulses. The cortex tries to bring order into these “intrinsically inchoate” impulses by releasing the stored memories of the sleeper and by then, in some as yet unknown way, “synthesizing” the impulses and the released memories to make up a dream. This synthesis gives to the dream a certain form; and Hobson describes the features that make up the form of a dream.

First, a dream has a hallucinatory character, because the dreaming brain is cut off from external sensory input, and has “no choice but to interpret its internally generated signals in terms of its previous experience with the outside world.” Secondly, a dream is a delusional experience, because the brain has “no external cues” to rely on, but only its own internal store of memories. A dream is also characteristically a bizarre experience, full of distortions of time, place, and persons, because the transmissions from the brain stem are randomly activated, and the forebrain is able to give them only an inadequate coherence and meaning. Hence, Hobson argues, psychoanalysts are wrong in believing that dreams are bizarre because the sleeping person defensively disguises unconscious material, such as repressed wishes.

Another formal feature of dreams is to be found in the “intense feelings (such as anxiety, fear and elation)” characteristic of some dreams. This feature, Hobson writes, comes into play when the emotional centers of the brain are activated by the nerve impulses from the pontine region. Lastly, most dreams are forgotten. For this Hobson offers a speculative explanation. He thinks that because the aminergic neurons become arrested in their action during REM sleep, they prevent the forebrain from including the dream experience in our store of longterm memories. The dreams that we recall are those that are “temporarily” housed in our “fragile short-term memory” store.

Hobson’s account of dreams is clearly more limited in its scope than the presentation in his book may lead us to suppose. He is not interested in dreams that are largely made up of thoughts—not of visual images. That is, he is not interested in the typical dreams of non-REM sleep but only in those of REM sleep, which characteristically take the form of perceived images. Furthermore, it is also evident that Hobson is not interested in the atypical dreams of REM sleep, for example, dreams in which the person is aware during sleep that “it’s only a dream,” and which, therefore, can hardly be said to have the formal feature of being a delusion. I am not sure how he would try to explain these other sorts of dreams. What Hobson is really concerned to explain is the characteristic and typical dreams of REM sleep.

The next step in his explanation of these dreams is the crucial one. When the neural activity in the brain stem reaches the cortex, the cortex achieves a “synthesis” of the random impulses reaching it. As a result, the dream acquires a specific content of a kind that can be apprehended, and this is what the dreamer is aware of when he remembers the dream.

Now Hobson draws attention to two beliefs about this content that are part of the psychoanalytic view deriving from Freud—beliefs that Hobson firmly rejects. According to the psychoanalytic view, the real meaning of a typical dream of an adult is not to be found in the specific content that the dreamer is aware of and is therefore “manifest” to him. The real meaning is to be found in the unconscious wishes, fears, and so on, which the person is keeping out of his consciousness but which, in a disguised form, get past the defenses of the sleeper and become part of the dream, and thereby make up the manifest content that we are conscious of when we recall the dream. Psychoanalytic interpretation of the manifest content is required in order to uncover its real meaning, and so bring to light what is called the “latent content” of the dream. Hobson rejects this psychoanalytic view by arguing that “most dreams are neither obscure nor bowdlerized, but rather transparent and unedited.” They conceal no latent content. It is, he believes, reasonable to discern a “significant personal meaning” in the story of a dream without having to resort to psychoanalytic methods.


According to the psychoanalytic view, the energy that sets the dream going comes from one of two sources—either from outside the person, in the form of the memory of some happening during the previous day or some stimulus that threatens to disturb the person’s sleep, or from the instincts and internal bodily states and needs that are connected with instincts. (Sexual dreams accompanied by nocturnal emissions could be an example of dreams stimulated by such internal energies.) It is the concealed unconscious wishes and bodily states that produce and sustain a dream, along with the psychic conflicts to which they give rise.

Hobson rejects this entire view. We know now, he claims, that the brain generates its own energy, and this energy is quite sufficient to produce dreams. We also know that it is the release of the cholinergic neurons in the brain stem from aminergic inhibitions that causes REM sleep and dreaming. “Once REM sleep and dreaming have been cholinergically triggered,” Hobson says, “wishes may be expressed and may even shape dream plots, but they are in no sense causative of the brain process.” This is the fundamental premise of his theory. From it comes Hobson’s claim that an unconscious wish does not contribute in any way to produce a dream, and that psychoanalysis is mistaken in holding to its view that it does so.

Hobson supports and illustrates his position that dreams are “transparent” and can be accounted for by organic cellular processes by presenting and examining one of his own dreams. He tells us that in this dream he accompanies his wife to the Museum of Fine Arts in Boston, where she, in fact, works as program director, and hears a Mozart piano concerto there. He then goes to a smaller theater, and, opening the door, comes upon Mozart himself playing the same concerto he has just been listening to. He shuts the door quietly and wonders how to tell his wife of his discovery.

Part of the dream’s transparent meaning, according to Hobson, is that “I would love to see Mozart, to have my wife ‘score’ [in her capacity as program director] by attracting him to the museum, and to discover him there so that I could report her coup to others.” He has no need, he says, to look for any latent content—that is, for an underlying, disguised, and concealed meaning—as a psychoanalyst would do. Still, he does go on at once to say that “at a deeper level 1 am prepared to admit that this dream might have a psychoanalytic ‘meaning,’ ” which he offers us. “You hate your father and you want to kill him! But you can’t face that base wish, so you turn him into a great man and laud him.” This example of a psychoanalytic interpretation is unfortunate. Its obvious crudity, verging on caricature, does nothing to strengthen Hobson’s argument.

Hobson goes on in a single paragraph to contrast the supposedly psychoanalytic interpretation, in which Mozart is a stand-in for his father, with his own; and he asserts that any attempt to decide between these alternative theories of dream interpretation is “a literary game,” which psychoanalysis is likely to win because of its “eloquence and mystique.” His own physiological account, he claims, gets beyond all this by giving us a view in which dreaming is “organically driven and organically shaped so as to account for its distinctive cognitive features.” In the last part of the book he examines the dream journal of a man who reported more than two hundred dreams, many of which he illustrated with his own drawings. Hobson tries to show that by regarding dreams as transparent, he can find meaning in them without resorting to free association or the interpretation of putative symbols, as psychoanalysts would do. He ends the book by offering speculation, but no firm view, about why we sleep and dream at all.


How valuable is Hobson’s explanation of dreaming? To begin with, I will put to one side two preliminary difficulties. It is evident that Hobson continually moves back and forth in the book between neurophysiology and psychology, and he does not adequately take account of the different kinds of assumptions, language, and standards of proof that are peculiar to each. I shall ignore his confusions of the two categories in order to comment in his own loose way on his theory.

Secondly, his account has been criticized from within neurophysiology itself. For example, the neurologist G.W. Vogel has argued that Hobson has not shown that the giant cells of the pons in the brain stem are responsible for REM sleep, since they may set off activity in a similar way when the organism is awake. Nor has Hobson shown that dreaming is caused by firing these cells, since it has been found that other parts of the brain, apart from the pons—the hindbrain and forebrain—also seem to play an important part in producing REM sleep.2 But again, I shall ignore these highly technical objections, and give Hobson the benefit of the current doubts among neurophysiologists.

When we turn to Hobson’s theory, we face at once a formidable objection. I have said that his fundamental premise appears to be that since “cholinergic brain stem mechanisms cause REM sleep and dreaming, wishes may be expressed and even shape dream plots, but they are in no sense causative of the dream process.” This premise is simple-minded and mistaken. His account of the neurophysiology shows only that some specific activity of the aminergic and cholinergic neurons of the brain stem starts the dream process. He does not show us that this activity is sufficient to give rise to the visual experience of the dream in REM sleep. Of course, it may be the case that, for example, no wish, conscious or unconscious, plays any causal role in producing such an experience. But Hobson’s argument does not begin to show this—it is a manifest non sequitur—although he apparently thinks he has shown it.

The reason for this confusion, I suspect, is that Hobson has been completely misled by his use of the prestigious word “causative” (and its relatives “cause” and “generate”). I think he unwittingly restricts his use of the word to refer to the conditions that initiate something. This allows him to conclude that only the activity in the brain stem, and nothing else, can cause dreams. But this conclusion is true only because he has made it a tautology. Obviously, Hobson’s use of the word “causative” in this very limited sense does not justify us in excluding wishes from being a cause of dreams.

Naturally Hobson cannot adhere to his absurd argument for excluding wishes from having a part in causing dreams, though he argues that brain stem activity is causally responsible for the formal features of our dreams; he also says that wishes may be “expressed in and even shape dream plots,” and that the “brain-mind” processes “signals” from the brain stem and “interprets them in terms of information stored in memory.” On his own admission, therefore, wishes, stores of memories, and interpretation also have a part in bringing about a particular dream with its specific content. At most, all that his neurophysiological accounts can begin to explain are certain formal characteristics of dreams—for example that they are delusional, full of distortions, characterized by intense feelings, and that they tend to be forgotten. They do not explain how the brain comes to process signals and interpret them according to a memory store in a way that is sufficient to produce a particular dream.

From this it follows that neurophysiology does not, and cannot, at the present stage of scientific inquiry, explain the specific content of our dreams—why I had an anxiety dream last night about getting bad marks from Professor X, and you had a pleasant one about playing tennis. When we compare Hobson’s meager characterization of the formal qualities of dreams with the richness of a dream’s content, we can see how feeble his neurophysiological explanation is. It simply cannot explain what we are really interested in about our dreams, how they are connected with our waking problems and feelings, and our own characters. What is more, it obviously does very little to explain Hobson’s own dream about Mozart. All the discoveries that he and others have made about neuronal activity in the brain stem, and its effects on the cortex, can do little to explain why he should dream about someone playing a Mozart concerto in the Museum of Fine Arts, or anything else in his dream. He could drop all reference to neurophysiology, and his explanation of the dream as a consequence of his transparent wishes (to see Mozart and to have his wife triumph as program director) would remain—its strength and interest untouched. Elsewhere, in fact, he concedes that his neurophysiological theory cannot explain the specific content of dreams. But he does not appear to appreciate how much this concession detracts from the interest of his book.

Hobson supports his theory by means of another argument of a quite different character. He argues, as we have already noticed, that the energy involved in a dream is intrinsic to the neural activity of the brain. It does not come from—in Freud’s words—“the thoughts left over from the activities of waking life as ‘residues of the previous day.’ “3 Nor does the energy come from any instinctual impulse, sexual or otherwise. Here Hobson is getting at something true and important, though his way of presenting it again confuses neurophysiological and psychological categories. If psychoanalysts believe that the bodily energy involved in dreaming is always connected with states and events of a psychological nature, such as repressed thoughts, then in all probability they are wrong. The discovery of REM sleep, with its regular phases, made it highly plausible to suppose that dreaming is a reaction in part to some purely biological processes. Hobson’s work on the brain stem—in locating the source and character of these processes—has greatly strengthened the case for the importance of the biological processes that give rise to dreams. Psychoanalysts would be well advised to give up the view that the origins of a dream can be accounted for in purely psychological terms.

But this conclusion, I fear, does very little to support Hobson’s general position. Once the initiating conditions in the brain stem have gone to work, the psychoanalytic account can help to describe and explain the psychological processes that then take place. Consider Hobson’s example of his own dream about Mozart. It is not difficult to offer a more plausible psychoanalytic interpretation of it than the unfortunate one he provides himself. We might suppose that Hobson had a somewhat unpleasant experience the previous day: he found that his wife had received a nasty snub in her work as program director. We might also suppose that this experience damaged his own self-esteem, that he cannot accept it, and that he has an unconscious wish to restore and preserve his pride in her and himself. I could then explain his dream by suggesting that his unconscious wish appeared the following night in a disguised form in a dream in which his wife “scores,” thereby restoring his sense of his own importance. In this hypothetical explanation of his dream (which, of course, there is no reason to believe is true), Hobson’s wish has been able “to shape” the way in which the “signals” are “interpreted” (to use his own words) so as to give rise to his dream images.

Quite plainly, there is nothing in his own neurological theory that excludes the hypothetical psychoanalytic explanation that I have just given of his dream. Even if his theory were wholly acceptable in neurophysiological terms it is not sufficient to enable him to reject such psychoanalytic notions as the unconscious use of defensive disguise and repression, among others. The central notions of psychoanalysis may be delusive, but Hobson’s neurophysiology does not show us that they are. Hence he has no reason to exclude as valueless the contribution of psychoanalysis to the understanding of dreams; or, I suspect, the contribution of any other psychology that is current in the scientific and learned world.

Still, as we have noted, Hobson himself makes use of wishes to interpret the dream about his wife. And he agrees with psychoanalysts that dreams are “the mirror of our concerns.” Surely, then, the problem is to discover the respective contributions to the final product, the dream, made by the initiating and other biological conditions on the one hand and, on the other, by the psychological states and processes involved. Hobson does not seem to realize that his own arguments show that there is an intimate complementarity between neurophysiology and psychology at all levels of human functioning, and it is to these intimate relationships, surely, that he and other researchers should attend. I doubt whether most psychologists or historians of science will agree with him that Freud’s theory of dreams obstructed the study of sleep and dreams. But even if he is right here, it would be silly to pay no attention whatever to the psychoanalytic account of dreams. For we are still so ignorant about dreams that we should look at any contribution from any serious source, in order to see how it contributes to a scientific understanding of the dream.


In my judgment, then, the neurophysiology that Hobson presents does very little to support the overall view of dreams on which he bases it. The move from the one to the other is very weakly argued, leaving me to suspect that his view of dreams was derived from his own experience in psychiatry and not from neurophysiology. For he claims that by “looking deeply into” a “dream story” he can arrive at the transparent meaning of a dream, that he can “discern significant personal meaning without either free association or the interpretation of putative symbols.” In this way he arrives, he maintains, at a more plausible interpretation of the dream than the one that psychoanalysis can offer.

Wittgenstein objected to Freud’s account by asking in effect: How does Freud know that he stops at the right point in his search for the meaning of a dream?4 The same question can apply to Hobson. How does Hobson know where to stop looking in his own interpretation of a dream? Unhappily, he does not seem at all aware of the issues raised by this question. It would not do merely to claim that his own interpretations are simpler, more commonsensical, and therefore more plausible than those of the psychoanalysts. For simplicity may be misleading. (Remember Alfred North Whitehead’s guiding motto: Seek simplicity and distrust it.5 ) Psychoanalytic and psychodynamic practitioners could reply to Wittgenstein and defend their interpretation by appealing to what happens in the process of psychotherapy; they would point to the consequences during psychotherapy of actually presenting an interpretation to the patient: for example, the patient may immediately produce related memories, feelings, thoughts, etc. The analyst would claim that the dream interpretation under scrutiny helps to make the patient’s reactions and remarks coherent and intelligible, and hence that he is justified in accepting this interpretation and not going further. Hobson could adopt the same line of defense for his own allegedly transparent interpretations. But he does not do so, in spite of the emphasis he places on dream interpretation.

Nor can he plausibly dismiss discussions about the respective validity of his own views and those of psychoanalysis on interpretation as “a literary game.” When an analyst defends a particular interpretation of a dream by pointing to the patient’s reactions to it, and to the support for it from the experience of other patients, he is engaging in a rational discussion. No doubt theoretical preferences, previous training, personal tastes and idiosyncracies enter into the assessment of an interpretation and may have a large part in arriving at it. But we would be quite wrong to say, as Hobson does, that to enter such a discussion is to engage merely in a “literary game,” which psychoanalysis is likely to win because of its “eloquence and mystique.” For in rational debate over an interpretation the analyst can in principle be defeated by being shown to be mistaken in one way or another. It is certainly true, as Hobson says, that Freud’s theory is very different from Jung’s. But, again, it would be wrong to maintain that comparing these theories is merely a literary game. We can enter upon a rational analysis of the differing views of Freud and Jung, just as we do when we consider a particular interpretation. By failing to take account of such possibilities. Hobson reveals that he seriously misunderstands the logical character of the entire issue.6

Moreover, I suspect that the way in which Hobson contrasts the psychoanalytic explanation of dreams with his own will strike practitioners of therapies based on insight—psychoanalytic and psychodynamic, among others—as extremely simple-minded, and his treatment of the entire matter as unpersuasive. Psychoanalytic and psychodynamic therapists claim—and they are right to do so—that they can take the interpretation of dreams seriously only when the dream is examined with respect to the clinical situation, including, among other considerations, the history of the patient’s relations with the analyst, his abilities to understand and deal with his symptoms, and his other dreams. The psychoanalytic interpretation that Hobson offers of his own dream, in which Mozart is said to symbolize his father, is wholly removed from any clinical situation or evidence; and analysts may find that it reminds them of an exercise by a college student with no clinical experience, and with no knowledge of the psychoanalytic process.


Still, whatever the defects of Hobson’s book, it has some important virtues. It succeeds in bringing a rational and scientific light to bear on our dreams. In describing the contribution of neurophysiology, Hobson shows us, in effect, how biological states, processes, and events provide some of the necessary conditions for the occurrence of dreams. In doing so he takes some steps toward demonstrating how our dreams are “brain-based”—how, in other words, the neurophysiological states of the brain provide conditions at one level, that of cellular activity, for the emergence of the cognitive events of dreaming at a higher level. In this way, the synthesis of neural impulses that he postulates could be said to “subserve” the cognitive achievement of dream imagery.

His demonstration is perhaps most satisfactory where he shows how the character of neural activity in the brain stem is connected with the formal features of our dream life, such as its hallucinatory character. We have already noted, however, that Hobson tells us next to nothing about the nature of his postulated synthesis, or how precisely it determines the specific content of our dreams. He cannot tell us much more about the nature of the synthesis, since we still do not know very much about it; and this very defect in Hobson’s book has its own value in revealing how little we know about dreams.

The findings that Hobson and his colleagues have made about the neurophysiology of sleep and dreams have been obtained for the most part with microelectrode recordings from brain cells in cats. If we are to discover the neurophysiology underlying the cognitive achievements of the dreams of human beings, then at some stage we will presumably have to work with human subjects. However, since implanting electrodes in human brains is impossible now and may continue to be so, the window on the brain that Hobson and others have used so profitably in recent decades may be of only very limited further value. The ordinary reader, therefore, may be inclined to believe that scientific inquiry will never to able to fill the gap in our knowledge that Hobson has drawn to our attention.

I believe that the problem is not insuperable, and that Hobson’s own treatment of the subject helps to give it a mistaken appearance since he concentrates on only one method of investigation. In fact there are a number of other techniques and methods of investigation available to us in our search for the physical basis in the brain (“brain base”) for our cognitive functioning—techniques and methods whose value is very far from being exhausted. To mention only a few examples, there are new techniques of brain scanning, e.g., by positron emission tomography (PET); new methods of discovering how computations are performed by neuronal circuits; the use of experimental methods to explore brain damage in animals and man and the psychological consequences of such damage. We are not justified in being pessimistic about the power of scientific methods eventually to reveal the mechanisms of sleeping and dreaming.

Furthermore, Hobson implies throughout that the way to arrive at an understanding of the physical basis for our dreams is by directly considering the dream process itself. When he fails to keep his promise, the reader may become skeptical about the future of a science of dreams. However, the best way to get at the “brain base” of dreams, at this stage of our knowledge, is probably to adopt an indirect and gradual approach to them, not a direct and hasty one, such as Hobson could be accused of employing. For it should be obvious that dreams are very complex and fluid phenomena, difficult to pin down with sufficient precision for experimental purposes.

It may be much wiser, therefore, to approach dreams indirectly by remembering a well-known guideline in scientific inquiry—start with what you judge to be important, relatively simple, and capable of being explored by available methods of investigation. With dreams, this means trying first to reach a better understanding of the brain processes involved in learning, memory, and perception. Such understanding could give us a grasp of how the brain creates for us the internal representations of the world that help us to deal with our waking experience through concepts and symbols.

It seems very likely that in order to understand how learning, memory, and internal representations work we will have to discover, first of all, or at the same time, how neural networks in non-human animals are built and function so as to enable them to learn. In this field, microelectrodes are still central, and will probably go on being so for a long time to come. As soon as we begin to understand the relation of neural networks to animal learning, and to the simple symbolic or conceptual representations of which the higher animals are capable, we will then be in a position to use this knowledge to throw light on human learning, memory, and conceptual functioning. Discoveries about neural networks will obviously complement those from other branches of inquiry. Jointly, these findings will slowly enable us to put together a much fuller picture of brain functioning than we have at present. In addition, of course, we may before long find ourselves in possession of new and powerful techniques of investigation that we cannot even begin to imagine now. Did anyone, for example, ever contemplate sixty years ago the use of microelectrode techniques and Hobson’s window on the brain?

It is therefore a mistake to be pessimistic about our ability eventually to understand the basis in the brain of our cognitive functioning in general. There seems no reason in principle that the gap between our knowledge of the brain stem and of our dreams cannot be closed. But we may only arrive at this knowledge after we have discovered the neurophysiological basis of our waking cognitive activity. Meanwhile theorizing about the nature of dreams is bound to be tentative, and there is much to be gained by rejecting dogmatic formulations and recognizing how little we know.7

This Issue

June 15, 1989