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How does the human brain produce your private world? In this groundbre aking exploration, neuroscientist and author Susan Greenfield demystif ies the private life of the brain. She examines the physical basis of our emotions and searches for the answer to one of the most enduring m ysteries in modern science: How does the brain create a unique, subjec tive experience for each one of us? Utilizing cutting-edge research an d compelling personal anecdotes, Greenfield reveals that emotions, tri ggered by individual ...
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How does the human brain produce your private world? In this groundbre aking exploration, neuroscientist and author Susan Greenfield demystif ies the private life of the brain. She examines the physical basis of our emotions and searches for the answer to one of the most enduring m ysteries in modern science: How does the brain create a unique, subjec tive experience for each one of us? Utilizing cutting-edge research an d compelling personal anecdotes, Greenfield reveals that emotions, tri ggered by individual life experiences, are the very foundation upon wh ich our brains build our unique minds. In this absorbing, lyrical expl oration, Dr. Greenfield presents a provocative new theory that provide s an illuminating glimpse into the human brain and reveals the astonis hing essence of who we are.
Explains how childhood experiences, emotions, & drugs affect our personalities; incl. case studies & examples.
If someone told you that tomorrow you would lose your consciousness forever, how would you feel? Perhaps that you might as well be dead. And yet if your fate were commuted instead to losing your mind, then your prospects, though not very palatable, would seem less gloomy. Your consciousness and your mind, therefore, cannot be the same thing. This book is all about what these two distinct entities actually are and how they might relate to each other.
For as long as I can remember, I have been fascinated by how such sophisticated and elusive concepts fit in with what we know about our sludgy, physical brains. After all, your unique, highly personal view of the world—your mind—hardly lies in the mechanical workings of your liver, heart, or lungs. As medical technology marches forward, these vital yet impersonal organs will be transplanted with increasing ease and frequency. Working as I do every day on the chemistry of the brain, I have to admit to some bias. Even so, it is the brain, after all, when assaulted by drugs, psychiatric and neurological disorders, and head injuries, that is primarily at the root of any changes in character, emotions, or consciousness. There, among the tangle of invisible cells, electrical impulses, and molecules ranging from the awesome intricacy of proteins to the spooky simplicity of gases, down there where time counts to less than a thousandth of a second, somehow a unique, subjective experience is generated in each one of us—an experience of consciousness.
One thing for sure is thatconsciousness always entails some sort of feelings. Until relatively recently, philosophers have had a monopoly on exploring this subjective aspect of the mind: the mystery and apparent miracle of how things actually feel to an individual. Such flimsy, subjective phenomena are traditionally an anathema to us newcomers in the study of the brain, the scientists. Brought up as we are on the basic rule of being objective, we prefer to tinker around with the physical brain. But by disregarding the obvious yet frustrating fact that consciousness is a highly private event, scientists are throwing out the baby with the bathwater: The philosopher John Searle has remarked that studying the brain without an interest in consciousness is like studying the stomach without an interest in digestion. As I see it, we need to be bilingual, by which I mean that we must investigate both the neuroscience—the physical workings of the brain—and the subjective phenomena of feeling. We must develop a familiarity with the issues involved in the study of both the physical and the epiphenomenal events in the brain if we are ever truly to understand either.
In 1799, a stone was found near the town of Rosetta, thirty-five miles northeast of Alexandria in Egypt. Dating back to 200 B.C., this tablet was bilingual: it bore inscriptions describing the benefactions of the then Pharaoh, Ptolemy V, in two languages, Greek and Egyptian. For the first time, there was a key to extrapolating the meaning of the previously mysterious hieroglyphics of the Egyptian language. What we need now, over two hundred years later, is a neuroscience Rosetta Stone—a system of matching up our sense of consciousness and what we feel with what happens physically in the brain. Only by so doing will we ever have a chance of understanding how a physical brain can be responsible for creating consciousness and the powerful phenomenon of emotions. But there are no obvious clues as to what this neuroscience Rosetta Stone might be.
Perhaps one of the most straightforward ideas is that each different region of the physical brain has its own mental function. This model of the brain suggests that we ought to be able to find physical centers for the production of emotions and consciousness. The notion of physical centers for functions is inspired by the fact that brains—of all animals—are divided into easily identified, discrete parts. All brains are symmetrical around a middle axis and have a surface that resembles a walnut and a cauliflower-shaped appendage (a region known as the cerebellum) at the back. There is nothing else like this in the world nor, as far as we know, in the universe.
Of course the shape of brains does vary from species to species. Look in any continental butcher's window, and you will see that mammalian brains, say that of a rabbit compared to that of a sheep, will look somewhat different. Each species has a brain with a distinctive appearance, the makeup of which is the product of evolution. Over the years different parts of the brains of different animals have expanded and prospered in importance, while others have remained relatively unchanged, all in accordance with the demands of the lifestyle of the species.
But despite variations in size from one species to the next, and in the exact configuration and relative size of different brain regions, the basic structure of the brain is the same. The most fundamental component, common to all vertebrates, is the swollen extension of the spinal cord, which contains all the neuronal wherewithal to breathe, generate biorhythms, and control the hormones that are pivotal in the regulation of food, fluid, temperature, and sex. This primitive brain stem is the pivotal core, enfolded around which are the more complex and sophisticated parts of the brain: it deviates relatively little in a vast range of species, from reptiles to humans.
A good half century ago, psychologist Paul MacLean advanced a revolutionary theory that accounted for the similarity of the brain stem from one species to the next. The bottom line was that the brain stem was the source of the driving power, the energy that underscored everything we did. In this sense MacLean's view of the function of the brain stem was akin to Sigmund Freud's Id—the provenance of blind, brute urges to copulate and attack, to create and destroy. These most basic building blocks of human behavior, argued MacLean, could be unmasked, independent of the niceties of an obvious or appropriate context. If someone murdered your spouse, you might hate him or her, with good reason. But the blind and unquestioning devotion stirred up by the Nazis in the Nuremberg rallies of the 1930s had far less rationale—it was an emotion ignited by the heat of the moment. In fact, MacLean cited behavior at the Nuremberg rallies as an example of the human brain stripped down to its reptilian essentials, whereby the brain stem operations are unleashed and allowed to run free. He proposed that emotions were, therefore, most of the time, suppressed in some way by logic and reason.
The great pioneer Sigmund Freud had first presented a version of this idea of unfettered mental forces a good fifty years earlier, with the concept of the Pleasure Principle. According to this principle, the drives of the Id served to reduce tensions, to uncoil a cerebral spring being wound up tighter and tighter by the Ego, the organized, rational aspect of brain function. The Ego normally held the Id in check: this supervisory Ego had no precise anatomical location, but was a kind of umbrella term for the cohesive set of memories and values, the individual view of the world, that characterizes the adult human mind. The Ego itself was suppressed still further by standards of critical morality—the Superego—a sort of conscience.
But Freud had abandoned neurology for psychiatry: he was interested not in the intricacies of the brain itself, but in why people thought and behaved as they did. Given the still sparse knowledge of neuro-physiology at the time and the even cruder research techniques, it is not surprising that Freud was not attempting to discover how such sophisticated processes could be realized from the mire of the physical brain. Instead, it was MacLean, benefiting from the progress of several decades of brain research, who identified a particular part of the brain as crucial in the suppression of the basic urges. The limbic system describes a variety of brain regions that cluster around the hub, or the brain stem, and thereby cushion and channel its atavistic demands.
To a certain extent, the idea of this conglomerate of regions as the regulator of emotion has been borne out. In many cases, damage to the limbic system results in inappropriate emotion. For example, Klüver—Bucy syndrome occurs when a certain part of the limbic system, the amygdala, is damaged. Patients exhibit a high sexual drive, directed not so much toward a prospective partner as toward anything around them, even inanimate objects. Along similar lines, removal of another region, the cingulate cortex, in experimental animals results in "sham" rage—a pattern of behavior that contains all the outward features of a genuine, infuriated state but that occurs for no obvious reason.
Blanketing the limbic system is yet another layer of brain, the cortex, Latin for bark. This structure is so named because it wraps around the rest of the brain, forming an outer layer as its arboreal namesake does around a tree trunk. The cortex is spectacularly exaggerated in our own species, double the size in places that it would be for a primate of our size. Because its surface area is so much larger in primates in general, and because damage often leads to relatively sophisticated impairments of thought, the cortex has quite reasonably been assumed to be involved with logic and the ability to rationalize.
MacLean had the novel insight that not only was the brain stem held in check by the limbic system, but that the limbic system in turn was suppressed by the cortex. This idea was inspired by the fact that the cortex is, even to the naked eye, clearly a distinct structure from the limbic system below it. In dissection the two areas prize apart cleanly and easily, like the skin from the flesh of a tangerine. Although it was Freud who drew a distinction between what we want to do and our final censored actions, it was MacLean who pointed specifically to distinct physical brain regions, respectively attributing them with emotions or thought processes. Because this idea of a brain hierarchy seems intuitively attractive, and because the brain anatomy seems to correspond to a neat and rigid escalation in abilities, scientists and nonscientists alike have accepted for decades the paradigm that emotion and logical thinking —so-called cognitive processes—can be segregated.
Some might even have been tempted to associate a certain brain region—the prefrontal cortex—with the generation of personality. One of the earliest and most famous cases that drew attention to the prefrontal cortex as a candidate "center for" personality took place in Vermont, in 1848: Phineas Gage, a railway foreman, was tamping down dynamite with an iron bar when the explosive detonated prematurely. The four-foot-long tamping bar, thick as several fingers, was shot through the front part of his brain. As the story goes, incredibly, none of Phineas's faculties seemed impaired. His movements and speech were normal, and all his senses were intact. There was just one problem: over the next few months, Phineas's whole demeanor changed from that of an easy-going team player to a quick-tempered and uncooperative egocentric.
Almost a century later, a Portuguese neurosurgeon, Egaz Moniz (1875-1955), heard of a procedure whereby destruction to—a lesion of—the front part of the brain suppressed "neurotic" behavior in a monkey. As a consequence, in an era when the mentally ill were simply put in straitjackets, locked into padded cells, or injected into insulin comas, Moniz developed a seemingly most humane, surgical treatment for violent patients that was soon extended to a variety of mental disorders: leukotomy—literally, "cutting the white matter? White matter is the general term used for the fiber connections between groups of brain cells, in this case the connections between the frontal lobes and the rest of the brain. The aim of the leukotomy procedure was to isolate the prefrontal cortex so that it no longer could play any part in the functioning of the patient's brain, and hence of his or her life. At a time when drugs for psychiatric conditions were hardly heard of, leukotomy came to be used as a treatment of choice to calm down agitated and aggressive patients right up until the 1960s. Those who had undergone surgery became so calm that they were often listless and completely unmotivated.
Now, if changes in the physical brain underlie changes in character, it seems reasonable to search for a physical provenance of our "selves." But as it turns out, the brain cannot be so easily compartmentalized. We now know, thanks both to clinical observation and to neuro-scientific research, that there is no simple one-to-one matching between a function and a particular part of the brain. For example, in the generation of movement, at least three different extensive systems in the brain are involved, each with a different aspect of motor control. Instead of a brain region being an autonomous center for this or that, it seems more likely that areas of the brain, especially zones within the cortex, work in a way that is more reminiscent of the interactive harmony produced by instruments in an orchestra. On the one hand, many instruments converge to contribute to a single moment of sound in a symphony; yet any one of those instruments will make very different sounds when playing a work by Stravinsky versus one by Wagner. A comparable convergence and divergence are at work in the brain: any one function depends on the contributions of many brain areas, yet any one brain area will participate in any number of diverse functions. For example, the visual system uses at least thirty different areas of the brain, while any single region, such as the prefrontal cortex, which lies behind the forehead, has been associated with functions as diverse as depression, memory, and as we have seen, personality itself.
Also arguing against a simple structural provenance of our selves in the brain is the fact that one human brain looks so much like another. If your and my prefrontal cortices were laid side by side on a slab, they would look more or less identical. So, it is still far from obvious to see where the individuality of each human being might creep in: we will have to search for some further clue, buried somehow, somewhere in the actual fabric of the brain, within each region.
This fabric of brain tissue, from which each brain region is made, can be broken down into complex, overlapping interstices of circuits formed in turn from vast numbers of brain cells, neurons. The 100 billion neurons in the adult human brain have been likened previously to the number of trees currently in the Amazon rain forest. Yet I now think that a bustling metropolis, like New York City, would be a better analogy. New York City can be divided up on a gross scale into different boroughs, then into different districts and neighborhoods, and finally into blocks. But within each block there is an incessant activity both restricted to local spheres of influence as well as interaction with the "higher" levels of neighborhood—district, borough, and so on. Any one room in a building on a block could, perhaps, be fancifully likened to a neuron. The constant activity within any building, with people darting, lingering, resting, and rushing between rooms and out into the wider world of the street and the city itself, would be similar to the chemicals, or transmitters, that are used as messengers from one brain cell to the next. Transmitters are used to bridge the gap, the synapse, between neurons. First, one neuron generates an electrical signal lasting a thousandth of a second, and of an amplitude ranging anywhere from some sixty thousandths to ninety thousandths of a volt: this is the action potential, an electrical blip that hurtles down to the end of the neuron at speeds of up to 250 miles per hour. Once it reaches the end of the neuron, the electrical impulse acts as a trigger for the transmitter to be released. The transmitter then diffuses rapidly across the narrow synapse between the two cells, and joins in a molecular handshake with an appropriate custom-made chemical (receptor) embedded on the outside of the target neuron. This molecular handshake, perhaps more akin to a hand fitting in a glove, initiates the final step, the generation of a new action potential in the target cell. This process, synaptic transmission, is the best-known mechanism by which brain cells communicate with one another; it is regarded as the basic building block of virtually all brain operations.
Let's stretch the New York City analogy to the breaking point. We can now reduce brain operations to a level even smaller than the neuron itself, to that of the synapse—the behavior of a person constrained by the dimensions and layout of a room that perfectly fits their needs to eat, sit down, or stretch out. And even at the synapse the units can be broken down further, analogous to the person opening a certain cupboard and reaching for a certain glass. There are, for example, channels in the wall of the cell that allow ions such as sodium and potassium to traffic between the interior and exterior of the neuron, and so change its voltage (the imbalance in charge between the inside and the outside of the cell). This interplay of ions results in the all-important, highly transient electrical signal. There are pumps in the cell wall, too, a little like molecular revolving doors, that allow the ions to return to their original sites once the electrical signal has been generated.
Given this complexity of structures in the brain, a next reasonable question might be what creates each of these structures and controls their functions. One part of the answer is clear: genes. Each of the hardworking complexes of molecules in the brain—ion channels, ion pumps, transmitters, and receptors—will have, as do the myriad other components of the neuron, different genes responsible for their expression within different circuits within the brain. So, if one of these genes is defective, clearly the transmitter, receptor, or ion pump will malfunction, and the whole system will become perturbed. Due to the apparent ease and agility with which molecular biologists now manipulate life-forms by manipulating their genetic makeup, the importance placed on genes has understandably swelled. There has even been talk of the "gene for" criminality, for homosexuality, or more recently, for good parenting skills.
So impressive is the power of genes that some scientists, such as the geneticist Richard Dawkins or the psychologist Steven Pinker, argue that the traditional focus on the Self as the most important unit of life is misplaced. The Self is largely unimportant in evolutionary terms, and to Dawkins or Pinker the course of evolution is the subject of primary interest. The most basic unit of life can be boiled down to the immortal gene as it is passed on from one generation to the next and serves as the ultimate controller of how each brain is made.
In this "reductionist" spirit, one of the Nobel laureates who discovered the structure of DNA, Jim Watson, claimed that ultimately all science was "reducible" from biology to biochemistry to chemistry to physics, and hence that everything other than physics was "just social work" This stark type of view has been robustly opposed by the biologist Steven Rose, who instead hypothesizes that every organism has its own "lifeline" its own trajectory in space and time that gives it a unique narrative. Rose has pointed out the fairly incontestable fact that genes on their own are, after all, merely a few strands of the nucleic acid DNA. The critical issue is how one component relates to another, how they are organized—be it one brain cell forming a synapse with another, a synapse forming with another into a circuit, many circuits forming brain regions, or brain regions forming into a brain.
My father used to enjoy telling me when I was a child that all we humans were was "ten shillings' worth of chemicals" (I am old enough now to have been young in the days prior to the decimalization of British currency). But what I never thought through in my ignorance and innocence was that there is of course far more to a body than a mere cauldron of chemicals: it is how these chemicals are actually organized within the cells of each organ, how in turn those cells are configured to make up each organ, and eventually how the organs relate to one another, that is critical. As soon as a system, be it a symphony or a curry or a whole human body or a brain, is reduced to its tiniest components, something special is lost.
Undeterred, the reductionist genetic train of thought furls the currently highly fashionable concept of a gene for this or that. Yet even a clear pattern of heritability can be misleading. Consider the most famous experiment demonstrating the inheritance of traits, conducted by Gregor Mendel in 1865. Mendel demonstrated a systematic and predictable appearance of traits in peas for, for example, one of two different colors, yellow or green. But we cannot infer from this observation that a percentage of the pea population in question had a "gene for yellowness." Instead, what Mendel had really identified were peas with a gene for an additional enzyme that destroyed the green pigment chlorophyll, which in turn played a part in the complex process of its metabolism. The net effect of yellowness was thus not due to a direct one-to-one matching with a single, autonomous gene responsible for a different color of pea.
Not only might many genes be for some such unsung, covert phenomenon as opposed to the observable end product, but the genes themselves are hardly independent little units of destiny. As a crude analogy, take a simple component of the internal combustion engine, such as the spark plug. It is an essential component of the car, but there is no automatic, autocratic ability to motor along conspicuously locked into its design. Placed on a coffee table, a spark plug goes nowhere and does nothing. Only when placed in the correct, complex context of the engine, with the engine placed in a car, is the spark plug's potential realized. Only then can the car operate properly—so long as a host of factors additional to the spark plug are also operational.
I am not arguing here that we are born as blank slates, but rather I am attempting to place the admittedly vital role of genes, literally, in context. We have seen that it is misleading to expect there to be a whole, macro brain region for a committed, single function. Following a similar argument, surely it is even more absurd to dissect the composition of the brain into even smaller parts and expect a sophisticated function to be preserved, locked into a few strands of DNA.
Now think again about the gene that contributes to the expression of a protein that will make up a channel in the wall of a cell so that ions can pass in and out. Or consider a protein that contributes to a molecular target, a receptor—any one of many types of tiny chemical sites opening out from the wall of a neuron that enables a transmitter to exert an effect on the target cell. How crazy to expect a one-to-one relationship between such a disembodied protein, the product of a purportedly autocratic gene taken out of all context, and the final outcome of the human brain—some sophisticated behavior or other.
Quite recently, some studies have tried to combine the ideas of "genes for" and "brain regions for" to understand the physical bases of the vagaries of human character, emotional disposition, and thought processes. Imagine an experiment where, by the wonders of molecular biology, you were able to shuffle genes around with such dexterity that you could engineer a mouse containing extra rations of either its mother's or father's genes, instead of the usual fifty-fifty arrangement. Eric Keverne and Azim Surani in Cambridge have actually succeeded in skewing the allocation of genes from one parent or the other. Of course, the resultant embryos, some of which survived the three weeks to full term, were hardly the murine counterparts of Marilyn Monroe and Errol Flynn—ultrafeminine or ultramasculine. But the brains of the genetically manipulated mice had higher concentrations of either paternal or maternal genes in certain brain areas. Paternal brain cells tended to aggregate in the limbic system—the area that MacLean and others after him have identified with emotions—while the maternal cells were found in the cortex, the area purportedly responsible for more cognitive processes such as abstract thinking.
Such observations do not prove, however, that intelligence is a feminine attribute and emotion a masculine one. All that we might be able to say is that the propensity for different types of mental processes would be genetically traceable to your father, others to your mother. Just because a trait is inherited from your father does not mean that it is a masculine one, any more than hemophilia, say, is feminine, simply because, as in the notorious example of Queen Victoria's family and her great-grandson, the doomed son of the last czar of Russia, it is passed through the female line.
A further worry with this type of interpretation is that it still rests on the assumption hearkening back to MacLean, that emotions and reason are separate and mutually exclusive phenomena: the idea of emotions and instincts from father, and a mutually exclusive intelligence from mother, is predicated on the old paradigm that each process operates exclusively within one area or the other, either the limbic system or the cortex.
There is, however, a possible alternative interpretation to account for the predominance of maternal-derived cells in the "higher" centers, paternal ones in the "basic" areas. The issue could simply be one of certain genes favoring a fast rate of brain growth. Wherever such genes were operating, the brain region might grow faster and end up larger. My reason for suggesting this more humdrum scenario is that, as well as the cortex, another structure lying deeper within the brain and more associated with thoughtless generation of movements—the striatum—turns out too to be rich in maternal-only cells. Both these areas, cortex and striatum, are actually quite bulky: in contrast, the more superficial limbic system structures, the septum and amygdala—which are conspicuous for being chiefly composed of paternal cells—are relatively modest in volume. It is possible then, since the maternal genes in this study appear to favor growth of the brain in general, that it is beneficial for these genes to go to work in whatever brain regions happen to be larger—where more cells will be needed anyway. This is just an idea, but one that illustrates that there is at least one alternative for which the maternal or paternal genes, in this case, might truly be "for."
Of course, that does not mean that gross modifications in function will not result from loading the genetic dice in one brain region or another. The severe disorders of movement and mental ability seen in Angelmann Syndrome, or disorders in sex and eating drives that characterize Prader-Willi Syndrome, for example, are undoubtedly genetically related impairments. But we do not know what the direct product of the gene actually does, what the gene is, after all, "for."
There is no doubt that our genes play vital roles in shaping our personalities and regular behavior, just as a spark plug does for a car. But our mental functions, whatever they are, are in no way reducible to the products of our genes. In fact, the degree to which overall brain operations are genetically preprogrammed varies from one species to the next, and with that variance the potential for individualization also varies. In the case of goldfish, say, the genetic blueprint for a generic goldfish brain is pretty much unencumbered by interference from what happens to the individual goldfish, swimming out his or her fishy existence in the uneventful environment of a glass bowl. If a pet goldfish happened to expire overnight, a substitute rushed in early the next morning would circumvent the need to break the otherwise upsetting news to one's offspring. The behavior of the substitute would be indistinguishable from its deceased counterpart. As the brain becomes more sophisticated, however, it is increasingly hard to regard individual animals as interchangeable. The swift trip to the pet shop would be less likely to work even for a hamster that had been used to handling, and of course would not even be countenanced over the death of a pet cat or dog.
To illustrate the point that genes alone cannot simply control or create our personalities and behavior, the neurologist Richard Cytowic has made the following, illuminating calculation. The number of human genes has been estimated to be at most about 1,000,000. The number of synapses in the adult human brain, however, is far more, some 1,000,000,000,000,000—which is 1,000,000,000 times in excess of the basic genetic elements. These connections between brain cells are, to return to the New York City analogy, a little like the rushing of people in and out of a building, as well as within it: connections constitute an intermediate level in brain organization between genes and macro brain regions.
So if we now turn to the vital role of the connections between brain cells, we are led to consider the role of the chemicals in the brain that operate through a network of synapses. What happens when the processes of chemical transmission across synapses are stirred into a maelstrom by drugs? Certainly, the effects of alcohol on character are all too familiar in turning a pleasant and considerate human being into, for example, a belligerent or sullen bore. Similarly, the dreamlike stupor of the heroin addict and the literally "mindless" state sought by those who take Ecstasy all suggest that changing levels of brain chemicals play a vital role in changing states of consciousness. So are brain chemicals the key to the generation of our subjective feelings?
Just because changes in the chemical composition of the brain can change personality does not mean that we can simply attribute a change in personality or behavior to the chemicals themselves. Recently, on a science program on national TV, I have heard speak of one transmitter, serotonin, as the "chemical brake" on behavior, while another, dopamine, was described as the "molecule for pleasure."
To think this way is to revisit precisely the same fallacy as the "gene for" or the "brain region for" some type of behavior or cognitive function. It is yet again the same old idea that we should be able to express a sophisticated, outward function in terms of one brain feature alone—if not a gene or a brain region, then this time, a chemical transmitter. Rather, the real challenge is to incorporate brain chemistry into a new way of looking at overall brain operations that can also apply to subjective feelings: the neuroscience Rosetta Stone.
One exciting area of research in neuroscience with some promise in this endeavor is the study of brain plasticity, where physical changes can be seen in the degree and extent of connections between neurons in certain brain regions, as a result of injury, or more commonly, simple everyday experience. As the brain becomes more sophisticated, it appears to exploit instinct less and less and instead uses increasingly the results of individual experience, of learning. Hence individuality, I would argue, becomes more evident: the balance starts to tip correspondingly away from nature toward nurture—the effects of the environment. It is in this personalization of the brain, crafted over the long years of childhood and continuing to evolve throughout life, that a unique pattern of connections between brain cells creates what might be best called a "mind." I shall be trying to show that the mind should not be regarded as an airy-fairy alternative to the physical brain but that, at the same time, it is something more than a generic lump of gray matter. My particular definition of mind will be that it is the seething morass of cell circuitry that has been configured by personal experiences and is constantly being updated as we live out each moment.
So, important factors in making you, a human being, the person you are, are the personal experiences that you alone have had—what amounts to your memories. If you buy into my suggestion that the mind might well be the personalization of the physical brain, and if the personalization of the physical brain is driven not so much by genes as by individual experiences, then the concepts of memories, mind, and Self will be very closely related.
On the other hand, there is still something more to my state of mind at this very moment other than a mere inventory of all the things that have happened to me in my life. I like to think of myself, as I'm sure you do too, as a holistic and essentially feeling entity.
For example, one Christmas vacation, on a long flight my husband and I were taking from London to the Caribbean, a woman was caught persistently smoking in the rest room: unlikely as it might sound, she actually ended up being physically restrained in a straitjacket and handcuffs, two rows behind us, screaming. I felt a strange combination of what in retrospect I can label as alarm and anger: my heart automatically thumped through my chest and my throat went dry. I felt as though I was being taken over by reactions that I had not consciously initiated, and which I could not control. Yet it was an experience within my own private interior. No one else could climb into my body, to experience the particular sensations I was accessing firsthand.
No doubt my fellow passengers were experiencing some state that was indisputably just as private but comparable—even similar—to my own. After all, emotions are far more predictable than thought: most of us would feel extreme sadness at the death of a parent, or anger at someone caught stealing one's car, or love as we stood by our new spouse at a wedding. The outward responses, too, are so similar that they can be described in the same single word and documented, as they were by Charles Darwin over a century ago, as common coinage between all humans, for instance, joy, high spirits, surprise, fear, and horror. Everyone who is happy expresses that emotion with the same facial expression—the universal smile. Similarly, it is hard to mistake anger in another human being, wherever one is in the world. If emotions are less individualistic, perhaps they are a very basic part of brain function, both in the animal kingdom as well as in each human brain.
Already we have seen how MacLean, and Freud before him, saw raw emotion as something unleashed from the bounds of calm reason. Yet the intuitively appealing idea of emotions as something different from our normal, logical state was far from new, even in the last century. The dire consequences of a clash between emotion and reason can be found in a play written almost two and a half thousand years ago by the Athenian author Euripides. Euripides wrote of two basic opposing forces within the human mind. His play tells of the Bacchae—women who were becoming uncontrollable due to their abandoned, ecstatic worship of Bacchus, the god of wine. The king, Pentheus, wishes to impose order and stop their orgiastic revels altogether. However, he is warned by the blind seer Teiresias that things will turn out very badly if he does. There are two forces in man, Euripides has Teiresias explain, the "wine" force and the "bread" or rational, force—as I would have it, a mind employing reason based on experience: both are needed in a dynamic equilibrium if one is to remain mentally healthy.
Now notice that a common factor in the Euripides/Freud/MacLean schemes of things is the basic assumption that when you are thinking, being reasonable, and indulging your individual memories, there is no emotion present at all. But surely the idea of no emotion at all is alien to our ideas of being human. Any friend or colleague who acts in a way seemingly devoid of emotions is soon disparaged as "cold-blooded," a mere lower form of automated life, or worst still perhaps derided as a "robot," some kind of oblivious entity with no consciousness within at all.
In a classic paper written in 1959, Bruno Bettelheim documented the moving account of "Joey, the mechanical boy." Joey's problem was that he saw himself as a machine: for example, in order to eat he needed to attach tubes to himself. He had to be programmed, and all his responses were carefully thought out first. After an extensive and largely successful period of treatment, Joey took part in a procession, holding a banner that read, FEELINGS ARE THE MOST IMPORTANT THING UNDER THE SUN. "With this statement" concludes Bettelheim, "Joey entered the human condition."
Since it is generally abnormal to behave like a robot, then surely the corollary is that feelings are actually with us to greater or lesser extents all the time. Although, as adults, we might not be oscillating between sobs, ecstasy, and terror, that does not mean that we have no feelings at all. On the rare occasions when there are no immediate problems in my lab, I am aware still of an underlying anxiety, a mental radar beam panning around and around, on the alert for trouble, strife, or stress. Similarly, everyone knows those fortunate souls who have a sunny disposition as they work their way through the day. People whistle and sing in the corridors of my institution, giggle and groan as they wait for the elevator. True, they are not being emotional in the usual sense of the word, but they could hardly be described as robots, bereft of all apparent feeling.
Emotions must somehow be incorporated into any neuroscience Rosetta Stone. My own view of brain operations departs early on from the simple Euripides/Freud/MacLean division of emotion versus reason, in that I am suggesting that some sort of basic emotional state is present whenever you are conscious. And if emotion is a phenomenon that is inextricable from consciousness itself, then it should be a high priority for neuroscientists. Yet surprisingly, emotions have to date received relatively scant attention. In basic physiology courses, for example, nothing is said of laughter, not even regarding its mechanical bases—those unbidden familiar contortions of muscle, breathing, and vocalization. It is almost as though laughing, and the emotion of happiness that engenders it, was too frivolous for the heavy machinery of scientific investigation. I remember vividly how in one student lab in which I demonstrated, the medical students were told by the senior member of the faculty that one of the side effects of morphine, along with constipation and constricted, pinpoint pupils, was euphoria—as though one of the most overwhelming experiences imaginable was something as banal as an intestinal contraction.
One notable exception to the coyness seen among many scientists regarding the study of emotion was a series of experiments carried out over forty years ago; this work was to initiate a particular approach that promised a glimmer of insight into the generation of emotions in the brain. Two psychologists, Olds and Milner, showed that a rat would repeatedly press a bar to stimulate its own brain in preference to any other activity in the rodent repertoire. The electrode via which the current was delivered had to be implanted in certain key regions, but then the animal would carry on pressing the bar until it was exhausted. The most obvious interpretation was that the rats were experiencing some sort of rodent pleasure. And if rats can feel some sort of pleasure, it is no great conceptual leap to point to the tail-wagging dog, the purring cat, and indeed the gurgling, grinning baby who can smile and laugh way before he or she will be able to speak or reason.
There is no way of knowing, of course, what the actual sensation is like for the rat, just as it is impossible to know what it feels like generally to go through life covered in fur, sporting a long scaly tail, and being able to jump from a standing start at least several times higher than your body height. As the philosopher Thomas Nagel famously pointed out with regard to bats, we cannot enter the skull of another person, let alone another species, to experience directly the emotions that rats or bats actually feel. All we have access to is the mechanical, external behavior that may or may not accompany a certain type of emotion. In the case of the bar-pressing rats, all we know for certain is that they are working for a reward: hence the brain sites eliciting self-stimulation would be more accurately described as "reward centers" than the arguably more tempting "pleasure centers."
Yet such studies do hint at a crude portfolio of different rodent emotions. There are also behaviors comparable, yet antithetical, to those of the frenzied bar-pressing of a rat presumably experiencing pleasure: over the intervening years, psychologists have made much use of the idea of aversion and aversive stimuli. In the behavioral sciences, it is possible, just as with self-stimulation experiments, to contrive scenarios where an animal, usually a rat, will make a demonstrable effort not to experience a certain outcome: a mild electric shock to the feet, or indeed stimulation to certain other parts of the brain that are anatomically distinct from the misleadingly dubbed pleasure centers—the areas of the brain that the rat will work to stimulate. An alternative scenario is to work to prevent stimulation: active avoidance. In this case, the strategic behavior on behalf of the rat can be distinguished from passive avoidance, since this time the rat will actually not take action—it will refrain from a behavior, in order to avoid a certain outcome. Just as the experimenter infers from the incessant bar-pressing of self-stimulation that the animal must feel some sort of pleasure, so they will also assume, when observing avoidance behavior, that the animal feels something unpleasant, such as fear.
But an emotion, a feeling such as fear, is not identical to a behavior such as avoidance. After all, as you lay sweating and terrorized in the lonely house in the middle of the night, you are undertaking no overt avoidance behavior, but you are still very frightened. Avoidance behavior, then, is a good reason to suspect that animals feel fear rather than concrete and exclusive evidence that they do. This distinction between what rats—or indeed people—do and what they feel is important to remember when tying to understand emotion.
Within the last few years, emotional behavior versus the subjective feel of an emotion has been dissected out, into different brain circuits. The neurophysiologist Joseph LeDoux has described an elegant segregation between two different anatomical systems in the brain, which correspond to two distinct processes involved in fear. The system that LeDoux uses is one comparable to that of the famous Russian psychologist Pavlov, who is of course celebrated for training dogs to salivate at the sound of a bell that they had been conditioned to associate with food. Similarly, in LeDoux's studies, an erstwhile neutral stimulus becomes associated with pain; in the future this previously innocuous stimulus will elicit a conditioned reaction of fear just as the familiar buzzer in Pavlov's experiments evoked involuntary salivation.
LeDoux has shown that conditioning a fear reaction in this way to an otherwise neutral trigger takes place using two simultaneous yet distinct systems in the brain. One circuit is via the cortex: the processing here is relatively lengthy but will eventually mean that one has a conscious experience of fear. By contrast, the second circuit bypasses the cortex: LeDoux proposes that this system has evolved not because some region below the cortex is, as MacLean would have argued, the emotional center of the brain, but instead because in evolutionary terms, processing of information via this route would result in quicker avoidance action, compared with a conscious response necessitating the scenic detour through the cortex. The particular brain region that lies below the cortex and that is the lynchpin to this "quick and dirty" circuit is the amygdala.
LeDoux's keenness to incorporate the amygdala is not particularly surprising, since that structure has long been implicated in emotion. As far back as 1939, lesions of the amygdala were used to suppress violent behavior, and indeed could lead to bizarre syndromes, such as the Klüver-Bucy syndrome we met earlier. Conversely, consider that electrical stimulation of this area in cats, for example, can lead to sham rage—a phenomenon where there is no obvious cause of the behavioral pattern of responses of flattened ears, erect fur, and spitting. So is the amygdala the "center for" emotion?
When I was small, one of my favorite comic strips was "The Numskulls." The Numskulls, living up to their name, spent their existence inside a man's head and got him up to no end of mischief. They looked a little like a three-year-old's drawing of a person, consisting entirely of a large oval head from which protruded, as an afterthought, four single lines as vestigial limbs. I was delighted recently when I was able to procure a slide from the original of some forty years ago: the benighted, balding hero is shown in cartoon profile, with his brain divided up into rigid compartments. Each Numskull is engaged in a particular job: there's the chip-eating zone behind the mouth, with each morsel being carefully passed along from one matchstick pair of arms to the next, while another is busily operating a telescope behind the eye. Yet a third department shows a Numskull sweeping the inside of the nose with a broom, while arguably the best job of all, in the highest compartment, involves a slightly irate Numskull screeching down a telephone, instructing general operations: the center for consciousness, no less. Much as one might smile at such a scenario, it is easy to slip into thinking that this is how the brain really does work, as though each distinct region were a mini-brain in its own right—almost a little person, with a separate brain of its own.
If we focus in on the amygdala with regard to emotion, then we run into the Numskull problem of regarding it as an autonomous brain within a brain, a "feeling" center. Just imagine the miniaturized brain of the Numskull himself: does it too have mini-Numskulls at work? Similarly, we might ask what happens inside the amygdala that is so special. If you were to look at the amygdala under a microscope, you would see a confluence of neuronal circuitry, like any other brain region. Of course the particular arrangement of certain groups of neurons would be special to the amygdala, but in itself this configuration would not bestow any unique, qualitatively distinguishable properties. The amygdala is an aggregation of many networks of neurons: not only has it no inner observer, but there is not even an inner proactive, driving force deciding what actions to instigate.
On the other hand, the amygdala is indeed in a key anatomical position, effectively an intermediary between the hippocampus, a region contributing to memory consolidation, and the hypothalamus, an area intimately involved in the regulation of hormones and thus with basic drives such as hunger, thirst, and sex. The amygdala, therefore, is a neuronal crossroads, perfectly positioned for the meeting of previously unassociated inputs converging from different brain regions. Herein lies its appeal to models of the brain, such as LeDoux's, where a behavior is learned as a Pavlovian reflex—a stimulus-response conditioning not requiring thought. But a confluence of anatomical pathways does not in itself offer an explanation of what an emotion, the actual feeling as opposed to the reflex behavior, actually is.
Emotional behavior, albeit unconscious, robotlike reflexes, is important as a key player in evolutionary terms—in survival value. After all, if a snake slithers across your path, it is important to take avoiding action as quickly as possible. LeDoux has argued that each emotion has evolved separately according to our evolutionary needs. Yet we still have no idea, if we follow his scheme, of the role of the amygdala, say, in differentiating rage from fear, or of explaining how the amygdala plays a role in positive emotions, such as pleasure.
A more basic problem still is that in LeDoux's scheme, a behavior is studied at the expense of the actual feel of an emotion. Emotion as a subjective sensation has been replaced by an emotional behavior—an objective, observable event. The important question here, of course, is what we think is the most important feature of an emotion. LeDoux sees the behavioral response with or without consciousness as the "wider" view: but I would disagree and argue that the whole crux of emotion is not so much the response but the conscious, subjective feeling itself of fear, or indeed, of pleasure. The concept of an unconscious emotion is, at least for me, a paradox.
In support of my particular disregard for mere behavior over actual feelings, other recent work suggests that what you feel, as opposed to what you do, can actually be differentiated inside the brain. Ned Kalin has shown, for example, that young rhesus monkeys will behave in the same way for two very different situations. These monkeys will coo either to express a desire for the mother's embrace or, on different occasions, will coo as a threat-induced plea for immediate help, because they are frightened. To us nonsimians this difference might seem like nitpicking—surely the two acts amount to pretty much the same type of emotional state. However, Kalin has demonstrated that according to the context in which the response is being generated, different chemical messenger systems will come into play. Surely then consciousness, one's prevailing inner emotion, cannot be equated with a stereotyped, outward behavioral response. My own conclusion is that emotion itself is independent of outward behavior, but is completely impossible without consciousness, and vice versa.
Unlike MacLean, Freud, and indeed Euripides, who treated emotion as an occasional outburst of a different type of brain state, and unlike LeDoux, who bypasses the feel of an emotion altogether, I am arguing for a different paradigm in which emotions are with us all the time, albeit at a spectrum of intensity. I am going to try and convince you that at one end of the spectrum pure emotion—the type of sensation experienced during road rage, a crime of passion, an orgasm, or at a rave—can best be viewed as the core of our mental states when, as when we are infants, feeling is not greatly tempered with individual memories, with cultural or private meaning, or, most important of all, with the self. Feelings just are.
When people lose their minds, blow their minds, or are out of their minds with fear or ecstasy, they are no longer accessing that highly personalized set of values, history, and unique view of life. They are no longer making full use of their personalized configurations of brain connections, which I have defined as the mind. Instead, they are traveling back to the time when they were very young, before such internal connections existed, when the external world therefore had no personal meaning, and indeed when they were swamped with emotions. Emotions, I am going to try to convince you, are the building block of consciousness. Emotions are with us all the time, to a greater or lesser degree, depending on how much you are using, or losing, your mind at any one moment. I shall be arguing that you cannot understand consciousness without understanding emotion, and that consciousness is not purely rational or cognitive as some, particularly those working in artificial, computational systems, have implied. Above all, not until we establish what emotions actually are and how and when they are generated—when we lose our minds or blow our minds—only then will we truly appreciate the mind itself. The idea that has prompted this book is that the more we are feeling emotional, the less we are accessing our individual minds, the less we are being ourselves; ultimately, we have let ourselves go!
Of course, this is just the outline—I would never imagine that you would buy into the idea just yet: you will be, I'm sure, wanting to see robust arguments and scientific evidence. But if true, then the idea would have profound implications, not just for how you understand the mind and brain, but more importantly, how you view yourself and your life. Why is it that we all seek to have more fun, but that anyone who spends his or her life as an out-and-out hedonist is usually the target of pity or scorn, rather than envy? Why do the activities we pay so much money to pursue, be it sports, partying, or travel, only sometimes bring the anticipated pleasure? Why do people take drugs? Is there any way in which we might better understand the scourges of modern life, such as schizophrenia and depression, and if so, will such understanding pave the way to better treatment? These are hardheaded, practical concerns that will be tackled in the journey toward the loftier goal of understanding how a brain weighing only some three pounds and with the consistency of a soft-boiled egg can generate the private world that only you know, and which makes normal living in any way different from virtual death—existence in a coma or simple sleep.
The conceptual corners I hope we shall turn are that: (1) emotion is the most basic form of consciousness; (2) minds develop as brains do, both as a species and as an individual starts to escape genetic programming in favor of personal, experience-based learning; (3) the more you have of (1) at any particular moment, then the less you have of (2), and vice versa.
The question of how the ebb and flow of a highly developed mind can be catered to by a physical brain, and the related question of how the one impacts on the other, are the hardest-ever challenges to human ingenuity and imagination. Yet we are living in a time that is unprecedented in its enthusiasm for probing the workings of the brain. At the most recent meeting of the American Society for Neuroscience, there were some 30,000 delegates who, collectively, could claim to have a very good idea of how our most personal body part is put together, how it develops in the womb, what it is made of, and what kind of processes and phenomena occur within it. Moreover they, or rather we, have access to meticulous reports of how the electrochemical intricacies that underpin brain function can be perturbed by injury or disease, as well as by drugs, both prescribed and proscribed. It is scarcely surprising, then, that an ever wider scientific constituency of biologists, mathematicians, physicists, and clinicians finally are gaining the confidence to break the monopoly of philosophers on the biggest and most tantalizing questions that we can ask about who and what we are.
Let's see first what progress has been made so far by both philosophers and the wider scientific community. We will then be able to go on and explore the extent to which the path outlined here is validated by empirical evidence, what the practical implications might be, and whether any new theoretical advance emerges as a result.
The Story So Far.
The Human Condition.