Saturday, April 01, 2000

Mind Energy

The Energy of Life: The Science of What Makes Our Minds and Bodies Work

By: Guy Brown, Ph.D.

Whether we call it energy, drive, spark, or spunk, we all rely on a kind of fuel that makes things happen. In this excerpt from his new book, The Energy of Life: The Science of What Makes Our Minds and Bodies Work, British biochemist Guy Brown sees how far modern brain science can go to explain this energy. His travels begin with Freud and end on the “small smudge of neurons” called the hypothalamus.


From The Energy of Life: The Science of What Makes Our Minds and Bodies Work by Guy Brown.  Reprinted by permission of the Free Press, a division of Simon & Schuster, Inc.

We speak of dynamism, drive, or spunk. We may seek them in employees, friends, or lovers —and most of all in ourselves. But is there really such a thing as “mind energy”? Although the concept smacks of “New Age” jargon, says University of Cambridge biochemist Guy Brown, it goes back at least to Sigmund Freud. In his new book The Energy of Life, scheduled for publication this spring by The Free Press, Brown asks what today’s brain science can say about the energy to “make things happen.” Following is an excerpt.

It sounds like a touchy-feely, age of Aquarius kind of idea. Can the concept of mind energy survive in the hard-headed and hypertechnological twenty-first century? On the other hand, we know that the essential qualities required to succeed at work and in life are motivation, spunk, drive, dynamism, ambition, sparkle, confidence, ability to concentrate and work without rest, to think fast and coherently—in short, energy. Every head-hunting agency is searching for that elusive quality of energy within the heads it hunts to energize a corporation or enterprise. Everybody is looking for that sparkle in friends and lovers to “make things happen.” Most of all, everybody is looking for that energy within themselves—the motivation, drive, and oomph to do something; the endurance, stamina, and resolve to carry through what we are already doing and need to do; and courage and will to break out of the old routines and change direction when necessary. We may know how to do something, but without the will and the energy, it is not going to happen. Without mental energy, there is no joy, excitement, or enthusiasm. Mental fatigue is almost a modern invention; depression and mental exhaustion appear to be epidemic in our society. Everybody seems to be crying out for more mental energy. But does this concept make sense in terms of the modern science of the brain?

Everybody is looking for that energy within themselves—the motivation, drive, and oomph to do something; the endurance, stamina, and resolve to carry through what we are already doing and need to do; and courage and will to break out of the old routines and change direction when necessary. 


The conceptual split between mind and body seems to have originated even before history began in the distinction between the soul and spirit that survived death and the material body that did not. As history evolved along its unsteady course, the spirits gained an ethereal quality and retreated into the brain. The triumph of mechanical explanation in science emboldened its champions to attack the brain itself and attempt to evict the spirits of mind from the citadel of the body. The birth of the energy concept in the middle of the nineteenth century appeared to present an opportunity for reconciliation between the ideas of dead matter and vital spirit. It was inevitable that before long, this energy concept, which had been so successful in physics and biology, would be applied to the mind itself. 

The origin of the modern concept of mind energy goes back to Sigmund Freud at the end of the nineteenth century, so it is appropriate to start our story of mind energy by following Freud’s own story. Fin-de-siècle Vienna was the stage for an epic scientific struggle, with all the ingredients of a blockbuster: sex, ambition, drugs, embittered friendship, tragedy turned to triumph, and more sex. The main protagonists were a young, ambitious doctor, Sigmund Freud  (1856-1939), and his older, more cautious friend, Joseph Breuer (1842-1925), plus the enigmatic, young, and beautiful fräulein, Anna O. The chemistry among these three produced a whole new science (or art), psychoanalysis; a new dimension to the mind, the unconscious; and two new forms of energy: mind and sex energy.

Freud started out as a neurologist studying the anatomy of the nervous system, under the tutelage of a great German physiologist, Ernst Brücke. Brücke was a founder, with Hermann Helmholtz, of the Berlin school of physiology. This movement sought to sweep the vital force out of biology and replace it with a deterministic science based on known physical and chemical forces alone. Helmholtz himself had been one of the founders of the concept of energy and had used the concepts and techniques of physics to study the nervous system and perception. He was the first person to measure the speed of signal conduction by nerves in frogs and humans, and his finding that nerve conduction was actually rather slow (closer to the speed of sound than the speed of light) startled the scientific community. This was because it implied that the brain itself was slow and that the world as we perceive it in the mind is delayed relative to the real, external world. Thus, Helmholtz believed that the world as we perceive it is constructed by the brain, starting with the raw sense data supplied to the eyes, ears, and skin, and that these data were molded into a perceptual form using “unconscious inferences” supplied by the brain. Most of the hard work in the brain is therefore unconscious and not open to conscious inspection. Freud was trained in this rigorous school of biological thought, based on hard physical materialism. And although his later ideas were based on psychological concepts not easily interpreted in terms of brain mechanisms, he always believed that his psychoanalytic concepts would and should eventually be replaced by a physiological explanation in terms of networks of neural excitation in the brain.

Later, when the wandering womb theory was shown to be anatomically unfeasible, hysterical women were said to have an “attack of the vapors,” as it was thought that noxious vapors from the womb were affecting the brain. 

Giving up physiological research, Freud underwent medical training at Vienna General Hospital and then took up private practice, specializing in the treatment of hysteria. Hysteria was an interesting psychological disorder that is not generally recognized nowadays but seemed to be prevalent in fin-de-siècle Vienna. In fact, hysteria was an ancient diagnosis of neurotic women. Hippocrates had attributed it to the womb’s (Greek hystera) wandering into other parts of the body. For example, the typical hysterical symptom of feeling a constriction of the throat was thought to be due to the womb’s becoming lodged in the throat. Later, when the wandering womb theory was shown to be anatomically unfeasible, hysterical women were said to have an “attack of the vapors,” as it was thought that noxious vapors from the womb were affecting the brain. Not surprisingly in Viennese scientific circles, dominated by Helmholtz’s School of Medicine, hysteria was not regarded as a suitably scientific subject for study. However, Freud had visited Paris to study under Charcot, a brilliant neurologist who had made the study of hysteria and the use of hypnosis fashionable and almost scientifically acceptable.

Freud tried to treat hysteria with all the latest medical fads, including massage, hydrotherapy, and electrotherapy, but they were all more or less useless. Hydrotherapy is a medical treatment by external or internal application of water and has its origins in ancient Greece and Rome. It was particularly popular in the eighteenth and nineteenth centuries, when health spas sprang up all over Europe. Charles Darwin used hydropathy extensively to treat his disposition to “excitement and fatigue” accompanied by vomiting, tremors, depression, and spots before the eyes. He built a bathhouse and every day would steam himself into a sweat and then shower in cold water, followed by a cold bath in the garden and scrubbing with a cold, wet towel until his skin was red and raw. Darwin certainly believed that this radical regimen was essential to maintain his energy levels. Hydropathy is not so popular now for medical purposes, but virtually everybody still uses hot and cold showers, hot and cold bathing, swimming, and saunas to lift their spirits and boost their energy. Why such treatment should be effective is not clear, but the sharp drop in body temperature when going from hot water into cold causes the release of adrenaline and stimulation of the sympathetic nervous system, which are major controllers of body and mind energy.

Freud also tried electrotherapy on his first patients. Electricity was very popular in the 1880s and 1890s for all kinds of ailments, both physical and mental. But the shock given by the electric torpedo was known to Hippocrates and was used by later Greek physicians by applying the torpedo to the affected part of the body, and was apparently particularly effective at curing headaches. In the eighteenth century, methods for generating and storing electricity, developed by Volta, enabled it to be applied to patients in either a static form or as a shock, and it was claimed to cure all kinds of ailments. In 1729 John Birch, a London surgeon, treated a hospital porter suffering from melancholia by passing six small shocks through the brain on three successive days. The porter regained his spirits, went back to work, and remained well for several years. ECT (electroconvulsive therapy) was born, although not widely used until the late 1930s. It still remains one of the most effective treatments for severe depression, although no one has a clue how it works.

The recent discovery of energy in physics and biology led to the new concepts of physical and mental fatigue, which became obsessions of the late nineteenth century. Thus humans had a limited store of mental or nervous energy, known as vis nervosa, which was dissipated by modern life.

Freud himself was not a well man. He suffered chronically from fatigue, nervousness, depression, and psychosomatic symptoms, such as diarrhea. In the late nineteenth century this constellation of complaints was called neurasthenia and was at that time one of the most frequent diagnoses in psychiatry. Asthenia means “weak” or “listless,” so neurasthenia means a chronic weakness or listlessness of neural or psychic origin. The name and diagnosis were devised by the American George Beard in the 1860s, and he regarded it as a nervous exhaustion brought on by the pressures of modern civilization. The recent discovery of energy in physics and biology led to the new concepts of physical and mental fatigue, which became obsessions of the late nineteenth century. Thus humans had a limited store of mental or nervous energy, known as vis nervosa, which was dissipated by modern life. The recommended cure was usually bed rest and isolation; thus genteel women with “nerves” were confined to their darkened bedrooms. 

The diagnosis of neurasthenia is still used occasionally today for mildly neurotic depressives, but it has mostly been replaced by chronic fatigue syndrome or ME (myalgic encephalomyelitis). Freud found that cocaine relieved his own neurasthenic symptoms and recommended it as the treatment of choice for neurasthenia. Cocaine and amphetamines can indeed relieve some symptoms of depression and fatigue, but with chronic treatment, larger doses are required, and withdrawal of the drug causes deep depression. Freud’s enthusiastic advocacy of cocaine led to its widespread use, and the subsequent discovery of cocaine dependency caused Freud acute embarrassment. 

In pre-Revolutionary Paris, Mesmer’s treatment was highly fashionable, particularly with women. Patients were treated in groups, sitting around a large barrel containing water and magnetized iron filings, from which protruded iron rods, which each patient grasped. Mesmer dressed as a magician and would himself magnetize the patients, to the accompaniment of soft music.

Freud also used hypnosis, a technique that can be traced back to the controversial Viennese physician Franz Mesmer (1734-1815), whose name gave rise to the term mesmerism. Mesmer used a type of hypnotism or suggestion on his patients, but he attributed his powers to a hitherto unknown physical-psychic force called animal magnetism. This force or fluid permeated the universe, and the human nervous system was somehow attuned to it. But an imbalance in animal magnetism within the body could give rise to nervous illness. So he treated patients either directly by channeling animal magnetism through his own body to the affected part of the patient by a kind of laying on of hands, or indirectly by “magnetizing” iron bars or other objects by touching them himself and then the patient used these objects to “magnetize” himself. In pre-Revolutionary Paris, Mesmer’s treatment was highly fashionable, particularly with women. Patients were treated in groups, sitting around a large barrel containing water and magnetized iron filings, from which protruded iron rods, which each patient grasped. Mesmer dressed as a magician and would himself magnetize the patients, to the accompaniment of soft music. Thus, there are striking similarities to both the modern laying-on of hands by psychic healers (for example, in Christian Science) and the use of “psychic energy” by new age, esoteric therapies.

The scale of Mesmer’s success caused a stir among conventional doctors and scientists, and the French government appointed a royal commission to investigate both his treatment and the existence of animal magnetism. This commission was chaired by Benjamin Franklin and included Antoine Lavoisier and Joseph Guillotin (whose invention was later to claim Lavoisier’s head), so it is clear that Mesmer’s ideas were taken very seriously, although skeptically. The commission’s report in 1784 concluded that animal magnetism did not exist, and the success of mesmeric treatment was due to the powers of imagination. Mesmerism was discredited, and Mesmer himself disappeared into obscurity. But mesmerism’s success did demonstrate the importance of powers of the imagination and hypnotic suggestion for medical and psychological treatment.

Much of the success of both the witch doctor and the modern doctor depends on the patient’s belief that the doctor will cure him, and this belief is aided by the modern doctor’s white coat, medical terminology, and scientific equipment, just as belief in the witch doctor is aided by his appearance, spells, and religious paraphernalia. This powerful psychological factor in medical treatment is now known as suggestion or the placebo effect and is an example of how the mind can heal the body rather than the body’s healing the mind. The effectiveness of psychoanalysis may also be largely due to suggestion or the placebo effect, but whether, if this were true, this would invalidate psychoanalysis is controversial. Freud would probably argue that the effectiveness of placebos in treating both physical and mental disorders is powerful supporting evidence for his ideas.

Freud realized that knowledge of the physiology and chemistry of the brain was advancing far too slowly ever to reach into the hidden depths of the brain. Confronted by the immediate problem of treating his patients, he had to use another route into the brain, which was to explore the psyche with the patient herself. But the patient’s consciousness had limited access to the psyche, so Freud had to develop various tricks, hypnosis, free association, and dreams to dig deeper into the murky world of the unconscious. And he found that the most effective treatment was the “talking cure” (or “cathartic method”) developed by Breuer and his hysterical patient Anna O.

Joseph Breuer had followed a career similar to Freud’s, only somewhat earlier. He had been a successful physiologist of the Helmholtzian variety and then one of the most sought-after private physicians in Vienna, while retaining a wide interest in science. In 1880 he began the treatment of an engaging and beautiful woman of twenty-one years. Her real name was Bertha Pappenheim, but she has gone down in history as Fräulein Anna O., because it was under that name that her case history was reported by Breuer and Freud in Studies on Hysteria, the work that launched psychoanalysis. She had developed a museum of hysterical symptoms, including a nervous cough, disturbances of sight and speech, inability to take food, and paralysis of three limbs. Moreover, she had split personality, one almost normal and the other of a naughty child existing in an altered, semihypnotic state of consciousness. In talking to her, Breuer realized that each of her symptoms was connected to a traumatic experience in her past, and the symptoms could be resolved if the patient relived the experience and its emotions in a hypnotic or semihypnotic state. Anna O. was highly intelligent, and she developed the technique of talking through her past experiences to relieve her symptoms one by one. The “talking cure” (or “chimney sweeping” as she called it) was born and remains the basis of psychoanalysis today. But it was a long and intense treatment that required vast quantities of emotional energy to be spilled by both patient and doctor. Breuer and Anna O. never discussed sex or sexual matters, and Breuer believed her to be asexual. However, they clearly became engrossed with each other, and Breuer’s wife became morosely jealous. When Breuer suddenly realized the cause of his wife’s moodiness and his own emotional involvement with Anna O., he abruptly terminated the treatment. He announced to Anna O. that their relationship was over as she was ostensibly cured. However, that evening he was called back to her house in crisis. She had regained her old symptoms and was now in the throes of a hysterical childbirth, apparently caused by Breuer’s attentions. Breuer calmed her down under hypnosis and then fled the house in a cold sweat. The next day Breuer and his wife escaped to Venice for a second honeymoon—or at least that is the story as told by Freud. 

Freud and Breuer developed the theory that hysteria and other psychological disturbances were largely caused by repressed sexual drives or experiences. This theory did not go down well in the world of late nineteenth-century Vienna and met mostly with a stony silence in the scientific community.

Freud and Breuer developed the theory that hysteria and other psychological disturbances were largely caused by repressed sexual drives or experiences. This theory did not go down well in the world of late nineteenth-century Vienna and met mostly with a stony silence in the scientific community. Breuer bowed to the zeitgeist of the times, and it was only with great effort that Freud persuaded Breuer to publish their findings together on hysteria. However, Freud was spurred by the opposition and championed the sexual theory with ever greater enthusiasm. He became frustrated with Breuer’s timidity, and their relationship was complicated by the large financial (and other) debts that he owed Breuer. They fell out, and Breuer retired completely from psychoanalytic research.

Freud’s emphasis on sex energy as an unconscious force in the mind led him to give it a separate name, libido, meaning the psychic drive derived from the sex instinct. The libido more or less continuously charges experiences, daydreams, and actions with a sexual edge. The evolutionary reason for this all-powerful psychic drive is obvious: the spreading of genes. But in a culture, such as 1890s Vienna, requiring the repression of most sexual expression, the repression of the libido causes psychic havoc, as most thoughts and experiences charged with libido fail to discharge, and instead fester in the unconscious, acting as sources of disruption for the conscious mind. Freud saw sex at the basis of most psychic disturbances. Thus, hysteria was due to repression of early sexual experiences, and neurotic anxiety was attributed to a failure to relieve an unbearable amount of sexual excitement, due, for example, to the practice of coitus interruptus or the engagement of a chaste but passionate couple. Similarly, neurasthenia was due to inadequate relief of sexual tension by autoerotic methods, such as masturbation.

Freud’s interest in sex alienated many, including two of his most able pupils, Alfred Adler and Carl Jung. But it had the opposite effect on the Austrian/American Wilhelm Reich, who made sexual energy the center of his analytic philosophy. According to Reich, the discharge of sexual energy during orgasm was the key to a happy, fulfilled life. Psychic blocks to the discharge of energy were manifested as muscular tension within the physical body. Reich claimed to be able to see this energy, which he called orgone energy, as blue particles down a microscope. And he designed and built boxes, “orgone energy accumulators,” which people could sit in to accumulate and enjoy this energy. Inevitably, Reich became increasingly isolated and paranoid as his theories were rejected, and he came to a sticky end when investigation of his accumulators by the FBI led to his conviction for fraud. He died in prison. However, his ideas lived on in the transmuted form of bioenergetics, a therapy devised by his American pupil, Alexander Lowen. Bioenergetics seeks to remove psychically generated blockages to the flow of energy by treating muscular tensions in the body in order to allow the full flow of orgasmic energy. Although Lowen’s therapy has not been particularly popular, there has been increasing recognition and use of physical treatments for psychological problems—for example, the use of exercise, massage, and yoga to treat depression, anxiety, and stress. Of course, as we have seen, this idea of treating the mind through the body originates much further back in history, to ancient Greece, India, and China.

Freud and Breuer’s theory of psychic function and motivation was based on mind energy. According to this theory, there are a number of unconscious drives, principally drives for food and sex, which provide the motivation for all our mental and physical actions. When a drive is active, it motivates the person by causing a discomforting tension in association with the idea of the object of that drive. For example, when the body is short of food, the food drive causes a tension in association with the idea of food, and we experience that tension as hunger pangs. We then seek to relieve that tension by hunting and consuming food. These actions relieve the tension, and we experience that relief of tension as pleasure. This is what pleasure is: the relief of tension set up by the drives. The basic motivation for animals and humans is the pursuit of this pleasure that we derive from relieving the tension, which is set up by the unconscious drives.

Freud called this theory of motivation the pleasure principle. The drives act as a source for the tension, which may be thought of as an excitation, charge, or energy. The drive sources are located in unconscious parts of the brain (ultimately this must be a group of neurons), or possibly the body—for example, the stomach in hunger. But the object of the drive is some conscious idea that is ultimately a different group of neurons in a conscious part of the brain. When the drive is operating, it transfers a tension, as an excitation, charge, or energy, from the source to the object. Once this tension is conscious, the organism seeks to relieve the tension (excitation, charge, energy) by discharging it externally or internally. Thus, when the sex drive is active, it acts as a source of a discomforting tension that charges up some sexual idea. Relief of this tension can be obtained by sexual activity. The relief of tension is experienced as pleasure.

When an unconscious drive charged a thought, experience, or area of the brain with energy, the process was known as cathexis, and when an area was overcharged, this was associated with a feeling of displeasure. Catharsis was the process of discharging that energy, which was associated with the feeling of pleasure. Normally the energy or emotional charge associated with an experience would be discharged by actions or thoughts prompted by it. But if the memory were repressed or the experience received in an abnormal state (such as hypnosis or fatigue), where it could not be discharged by the usual conscious processes, then the experience would remain charged in the unconscious and act as a hidden source of energy to excite and disturb conscious processes. Thus the therapeutic method invented by Breuer and Anna O., and elaborated by Freud, of recovering and discharging emotionally charged experiences from the unconscious was known as the cathartic technique. This method and approach are very much alive today in psychotherapy and popular psychology.

Fundamentally Freud and Breuer wanted to ground their psychological theory in terms of biology and physics, and thus they initially talked of their drives and ideas in terms of neurons and the tension in terms of “energy” or electrical excitation. In analogy to the first law of thermodynamics, Freud invented a law for this energy to follow, the principle of constancy: the brain tries to keep the level of excitation constant (or at a minimum). However, Freud and Breuer’s use of the concept of mind energy is somewhat obscure and ambiguous. In different contexts, it seems to refer to different things: metabolic energy, nervous excitation, emotional affect, attention, arousal, and mental activity. Ultimately their theory of drives, tension, and catharsis is a psychological theory of motivation. The theory could not be grounded in terms of metabolic energy or electrical excitation. Their use of the term energy simply functions as a metaphor for psychological tension.

I might be anxious about an exam, and I may relieve the tension produced by studying for this exam, but this anxiety was not derived from the endogenous drives for food, water, or sex; rather it was acquired externally from my peers and society generally.

Since Freud’s work, two different energy concepts have evolved in psychology: arousal, the general level of mental activity, which waxes or wanes with alertness or tiredness, and tension, variously described as anxiety, distress, psychological stress, or negative affect, but basically derived from Freud’s tension. Anxiety has been described as an acquired drive; it can function like a Freudian drive producing tension, but is acquired by learning or experience. For example, I might be anxious about an exam, and I may relieve the tension produced by studying for this exam, but this anxiety was not derived from the endogenous drives for food, water, or sex; rather it was acquired externally from my peers and society generally. Society approves and disapproves of various behaviors, and we acquire a sense of what is approved and disapproved of at an early age from our parents and peers. Freud called this internalized set of approvals and disapprovals (including morals) the superego, which produced anxiety and guilt when we violated society’s standards or contemplated doing so, but also produced pride or satisfaction at “doing the right thing” in society’s eyes. The superego was partly conscious and partly unconscious, and this could produce problems, as we might be unaware of the source of our anxiety or guilt. However, anxiety or tension can be a good thing. Anxiety is the most important motivator to do things within society. Without it, we might do very little, except fulfill our basic drives for food and sex.

In conclusion, we have two concepts of mind energy, neither of which directly relates to the metabolic energy of the body, although there are some connections. The arousal concept relates to the general alertness, sensitivity, and vigor of response of the nervous system. Arousal is well characterized at the psychological level and firmly based in the biology of the brain. The tension concept is less well characterized but refers to the stress, distress, or anxiety evoked by a particular stimulus or drive.


In a deep, dark valley beside a silent lake at the base of the brain lies a small chamber, the hypothalamus, in which all human passions are contained and harnessed to drive us on. This small smudge of neurons, less than 1 percent of the brain, is the drive center of the mind. In the driver’s hands are two sets of reins (known rather unpoetically as the autonomic nervous system and the reticular activating system), one of which controls the body and the other the brain. These two systems are the central controls over body and mind energy, respectively. They do not produce energy; rather, they aim to control it, as the rider controls a horse, spurring it on at times and reining it back at others. When we are spurred on, the body and mind are flooded with energy, and we give full rein to anger or anxiety, fight or flight, passion or drama. When the reins are drawn in, we relax and rest. And when drawn in further, we may fall asleep or into a depression.

The reticular activating system (RAS) is the arousal system of the brain. When activated by the hypothalamus or incoming sensory information, it wakes and alerts the brain and makes the brain attend to incoming information. It is like an alarm system telling the brain, “Wake up; pay attention. Something is happening.” But it also actively energizes the brain by spraying it with stimulant chemicals that make all the neurons more excitable, more sensitive, and faster responding. Without activation of RAS, the brain barely pays attention to incoming information; with extra activation of RAS, there is faster and more focused processing of the information. RAS wakes the brain and keeps it awake; it controls the sleep-wake cycle. RAS drives and motivates, and is involved in compulsion and addiction. RAS regulates emotion and mood, excitement and euphoria. RAS is the system targeted by amphetamines, cocaine, ecstasy, LSD, and Prozac. RAS is the mind energizer.

As we have seen before, the autonomic nervous system (ANS) is the arousal system of the body. It has two arms: the sympathetic nervous system, which energizes the body and prepares it for fight or flight, and the parasympathetic system, which relaxes the body after the threat has passed. Activation of the sympathetic system causes the fight-or-flight response. Chronic stimulation of the sympathetic system causes the stress response, a concept devised by the Canadian physiologist Hans Selye. Part of the stress (or rather distress) response is mediated by a separate system, the hypothalamic-pituitary-adrenal (HPA) system. This is a kind of third rein by which the hypothalamus controls body energy, and it is particularly active in anxiety and depression. In distress, the hypothalamus sends a message to the pituitary, a tiny gland below the hypothalamus, and the pituitary relays this emergency message to the adrenal glands, which then release the stress hormone cortisol.

Arousal is a key concept psychologists use to refer to the generalized activation or energization of the nervous system resulting from some stimulus. Myriads of sensory messages are continually sweeping into the brain from the eyes, ears, nose, tongue, and skin and generally pass through the brain, with relatively little attention being paid to them. But a particularly strong, new, or unexpected message sets off an alarm within the brain, causing both generalized arousal and focused attention. The arousal concept evolved from several different lines of research. The English neurophysiologist Sir Charles Sherrington (1857-1952) found that pricking a dog’s foot with a pin not only caused the reflex withdrawal of the foot, but also sensitized the dog to a whole range of other reflexes. A similar effect could be demonstrated in humans. People vigorously using one set of muscles could respond more rapidly to a signal. It appeared that stimuli (such as a pinprick) not only evoked a specific response (such as reflex withdrawal) but also generally alerted the whole nervous system, so that it became more sensitive and responded more vigorously to many (or all) other stimuli. The nervous system was aroused, and this arousal not only increased responses to external stimuli but also increased sensitivity to the internal drives. Thus, a rat given an electric shock would not only get annoyed, but also would mate and eat more frequently than it otherwise would do. Similar sensitizing effects can be shown in humans. For example, many people who are stressed eat more. Both women and men have been found to be more sexually aroused by an erotic film if, prior to that film, they have watched a vivid and gory film dealing with car accidents. The first film had no sexual content, but its shock value caused general arousal, which spilled over into sexual arousal when the second film was shown. Perhaps this would explain why Cronenberg’s notorious film Crash (based on J. G. Ballard’s novel) could make traffic accidents sexy. Some kinds of sexual foreplay involve biting, pain, or other forms of stimulation, which lead to greater sexual arousal. Some of us even find elements of humiliation essential for sexual arousal.

An ingenious and infamous test of the arousal concept was devised using two bridges over a river and one pretty woman. One bridge was 5 feet wide, 450 feet long, and swayed dangerously over a 200-foot drop to rocks beneath. Crossing this bridge was a high-anxiety, arousal experience. The other bridge, farther upriver, was solid and only 10 feet above a shallow river. Crossing this bridge was a doddle. Male subjects, men who happened to cross one or the other bridge, were met at the other side by a female experimenter who asked them to help her with a psychology project. The men filled out a questionnaire, and responded to a test that was later scored for sexual imagery. Finally, the experimenter gave each subject her telephone number, with the excuse that she would be willing to discuss the experiment with the subject if he wished. The men who crossed the low bridge scored low on sexual imagery, and only 12 percent phoned the experimenter, whereas the men who had crossed the high bridge scored high on sexual imagery, and an impressive 50 percent phoned the experimenter. The interpretation was that the frightening experience of crossing the high bridge had increased physiological arousal, and this had enhanced sexual arousal, resulting in the men being more attracted to the woman experimenter. Perhaps this research has application to the sex lives of politicians. Henry Kissinger once said that power was the greatest aphrodisiac, and the sex lives of some recent American presidents seem to confirm the theory that a high-adrenaline life can lead to a highly sexed life.

Arousal increases attention, concentration, and performance and can arise from many sources, for example, anger. Martin Luther King, Jr., reported, “When I am angry I can write, pray, and preach well, for then my whole temperament is quickened, my understanding sharpened, and all mundane vexations and temptations gone.”

Support for the existence of a generalized arousal system in the brain came from electrical stimulation of the base of the brain and recording the electrical activity (brain waves) from the surface of the brain. Electrical stimulation of the source of the reticular activating system within the brain stem resulted in generalized arousal in animals: they would wake up (if asleep), raise their heads, open their eyes, and look around alertly. If this area was damaged, the animals were drowsy, lethargic, and unresponsive. Thus this part of the brain is a general arousal or alarm center, which says to the rest of the brain, “Wake up! Pay attention! Something interesting is happening! Prepare to investigate and do something about it!”

The effect of stimulating the arousal center on the higher areas of the brain could be monitored using an electroencephalogram (EEG), an almost magical method for listening in to the brain waves coming from the surface of the brain without having to open the head. Electrodes are painlessly attached to the surface of the scalp and record the electrical activity coming from below. EEG was first used on humans by the German psychiatrist Hans Berger in 1929. He was very excited to discover different types of brain waves coming from his subjects’ brains in different states, from relaxation and sleep to full arousal. Berger thought that these electrical signals were due to some new form of psychic energy—P-energy, he called it. He believed that he had discovered the secret of ESP (extrasensory perception) and worked in great secrecy for five years. Eventually he was dismissed by the Nazis, became clinically depressed, and committed suicide. Berger was wrong about P-energy, but he had discovered something of great importance to brain function. The waves of electrical activity he observed were due to the synchronized oscillation of the electrical activity of millions of neurons at the surface of the brain. All of these neurons were firing in bursts or waves that were synchronized, so when they were all active at the same time, they produced a large electrical signal that could be detected on the surface of the scalp. However, this was not so in all psychological states. When the subject was asleep or awake but relaxed, the brain waves were large and slow, but when the subject was aroused or attending to something, the waves became small and rapid. It was as if when the brain was attending to something, all the different neurons had to do different things, their activity was not synchronized, whereas when the brain was relaxed and not doing much, all the neurons could be synchronized again, because they were not each involved in their own little tasks of information processing. Stimulation of the arousal center at the base of the brain caused the synchronized waves to break up into small, rapid waves. Thus, the arousal center does indeed seem to act as an alarm telling the rest of the brain to wake and get cracking.

Can we have too much or too little arousal? A number of lines of evidence suggest that too much or too little arousal can both make us unhappy and make us perform poorly in various tasks. When there are very high levels of arousal—for example, with high levels of fear, noise, or pain—mental performance decreases, thinking becomes chaotic, and there is a high level of anxiety. There may be an optimal level of arousal for any particular circumstance or task. Too little arousal, and we may have insufficient mental alertness to perform the task. For example, early in the morning or late at night, it can be difficult to focus on a task and process the relevant information. Too much arousal, and the increased sensitivity to stimuli and increased rate of thinking, may lead to mental overload and inability to concentrate on the task at hand. For example, flight controllers who are monitoring flights at an airport have been known to suffer from a type of sensory overload, causing loss of attention and concentration, on the task at hand. The same applies to the rest of us: a certain level of arousal is essential for optimum performance, but an adrenaline overload inevitably causes problems. 

We might expect people to feel relaxed and happy when their arousal level is low, but in fact the opposite appears to be the case when people are deprived of all stimulation for any extended period. Donald Hebb and his students at McGill University in Canada first studied the effects of sensory deprivation in the 1950s. Students were paid a substantial sum of money to lie in bed and do nothing for as many days as they could. This might seem like a student’s idea of heaven, but they were sensorially deprived, so they could not see, hear, or feel anything. Everything was fine for about a day, but then they lost the ability to think straight or concentrate. After forty-eight hours they could not do simple mental arithmetic; they began to see vivid images and hallucinations; they were desperate for any form of stimulation, even reading stock market reports over and over again. All students found the experience very unpleasant, and although they were paid substantial sums of money each day, most were desperate to escape after two or three days. Hebb concluded from this and other studies that people have an innate drive for arousal and stimulation. Underarousal or boredom is unpleasant, and we seek out stimuli to arouse us. But overarousal can be unpleasant too, and Hebb proposed that our response to increasing arousal was like an inverted U—hence the inverted U curve of arousal. If feelings are plotted against level of arousal, then at low arousal, we feel bad (bored), we feel better as arousal increases, and we feel happiest at an optimum level of arousal, but as arousal continues to increase beyond the optimum, we start to feel bad and anxious. This is the inverted U curve of feelings versus arousal—but the same kind of curve is found for performance versus arousal. 

Evolution appears to have primed us to seek out stimulation… If we are bored on a Sunday, we will seek out anything to tickle our neurons, even if it’s yesterday’s newspaper, which we have read twice before.

Our drive for arousal seems innate. If the arousal level is too low, we experience unpleasant feelings of boredom and frustration, whereas when arousal is optimal, it stimulates reward pathways in the brain that make us feel good or even euphoric. Arousal stimulates neural pathways and releases neurochemicals that make us high—the same pathways that are stimulated by cocaine, amphetamines, and heroin. That is why we like being excited. Evolution appears to have primed us to seek out stimulation. That is part of the reason we find ourselves reading books and newspapers, going to movies, socializing, snowboarding, and climbing mountains. If we are bored on a Sunday, we will seek out anything to tickle our neurons, even if it’s yesterday’s newspaper, which we have read twice before.


Just as chronically low levels of arousal and stimulation are unpleasant, so chronically high levels of arousal and stimulation can be aversive, but in a different way. Chronically high arousal is linked with anxiety. Anxious people are in a chronic state of high arousal. That does not mean that they are always highly aroused, but they are more sensitive than other people to real and potential situations or threats, causing them to be more often aroused, to a higher level, and stay aroused for a longer time. Anxiety is not just a state of hyperarousal; it also involves seeing the world in a negative way. And a very high level of arousal is not always unpleasant—it depends how it is viewed, in particular, whether the situation is thought to be under control or out of control. Imagine a roller coaster ride. You are looking down a particularly awesome hill; you can anticipate the fall, but your fear is under control. Then you begin to drop—the situation and your fear are out of control. The body and brain are flooded not just with adrenaline and noradrenaline, but also with the stress hormones cortisol and endorphins, preparing you for disaster. Eventually (a million years later) you hit the bottom of the hill, and the tension is released as laughter. The situation appears to be under control again, and the remaining adrenaline and endorphins produce a rush of euphoria—until the next time. We may get a similar roller coaster of the emotions from rock climbing or a horror movie. Arousal may be high all the time, but we can switch abruptly from euphoria to intense anxiety and back again, depending on whether we perceive the threat as controllable or uncontrollable. If we perceive the threat to our survival or well-being as out of our control, then we become anxious and release the stress hormones that are so damaging to our long-term health. Chronic anxiety is like living permanently on a roller coaster, but stuffed full of amphetamines or with an uncontrollable fear of heights.

Not everybody seeks out the same level of arousal. Some people are so-called sensation seekers or adrenaline junkies. They appear to need a higher level of arousal in order to feel good, and they seek out that arousal in social contact, sex, sports, or dangerous pursuits. Sensation seekers may start from a lower baseline of arousal and thus seek more, or they may be less prone to anxiety and thus can sustain a higher level of arousal without ill effect. Whatever the reason, the sensation seeker seeks to maintain his or her arousal level at a higher level than that of the average person, and considerably higher than that of the sensation avoider. Sensation avoiders have a low optimum arousal level, where they feel happiest, either because their baseline arousal level is already high or because they easily become anxious, so that even moderate levels of arousal promote anxiety. Thus they avoid situations and social contact that may push arousal levels above their low optimum.

Background arousal and the level of arousal people seek is one of the most fundamental aspects of personality. The controversial British psychologist Hans Eysenck argued in the 1960s that the essential difference between extroverts and introverts is that extroverts start from a lower background level of arousal and thus seek a higher level of stimulation in order to maintain themselves at a higher optimum level of arousal. Introverts start from a high baseline of arousal and thus seek a minimal level of stimulation or avoid stimulation in order to maintain a low optimum arousal level. Since social contact is a key source of arousal, extroverts seek social contact, while introverts may avoid it or seek types of contact that are less arousing or anxiety provoking.

Hans Eysenck’s life was certainly full of sensation, and it seems likely that he was a sensation seeker. He was born in Berlin during World War I and left Germany for the United Kingdom when the Nazis came to power in the 1930s. He became a professor of psychology at the University of London and studied the basis of personality and intelligence. He was an outspoken critic of psychoanalysis and one of the pioneers of behavioral therapy. He believed that intelligence is almost entirely genetic, and therefore that racial differences in intelligence are genetic too. This understandably caused intense controversy, which continues to this day in both the academic and public arenas. But his contributions to the theory of personality and the central role of arousal remain intact.

Eysenck’s theory was extended by Jeffrey Gray and Jerome Kagan in the 1980s to elucidate the biological basis of anxiety. Gray proposed that there was a pathway in the brain, which he called the behavioral inhibition system and which functioned during perceived threat to inhibit ongoing behavior, and redirect attention toward the potential threat. The behavioral inhibition system of people with chronic anxiety showed higher activity. These people were chronically inhibited and had their attention focused on potential threats. The brain pathway involved in this system partly overlaps with that of the RAS and thus is activated by arousal, but it also includes areas of the brain controlling behavior, attention, and emotion, and so has more specific effects on the brain. It has often been argued that arousal is intimately connected with attention. With low arousal, the mind is relaxed, the brain waves are slow and deep, and thinking is broad and diffuse; when arousal is high, the mind becomes focused and concentrated on the task at hand. Thus a certain level of arousal is necessary to concentrate on a task, as is obvious when we need to read and understand something late at night. But very high levels of arousal cause a reorientation of attention, away from thinking, toward the perception of potential threats, resulting in a hypervigilant state accompanied by intense worry. This may have been an advantage for a caveman, when the detection of threat was more important than general thinking, but it can be a nuisance for the overloaded modern businessperson lying awake at night contemplating potential threats in the urban jungle.

Jerome Kagan, a professor of psychology at Harvard University, has studied the nature of timidity in children. He found that some children are inclined to approach unfamiliar objects and people, and others are not—what he called uninhibited and inhibited children, respectively. These children are not just two ends of a spectrum of behavior, but rather two distinct types of people with a distinct genetic origin. One of the major differences between inhibited and uninhibited children is the level of autonomic arousal (the ANS and adrenaline); inhibited children have a higher level of arousal, just as Eysenck’s theory predicted. Kagan argues that inhibited and uninhibited children possess different thresholds for excitability of the emotional centers of the brain (the so-called limbic system and in particular the amygdala). Inhibited children have emotional centers that are more easily excited, and therefore activate the hypothalamus to alert the ANS and RAS and cause arousal, which in turn may activate the behavioral inhibition system, resulting in inhibition. In short, inhibited children are more “nervous.” By and large, inhibited children start out as inhibited babies and grow up to be inhibited adults. Inhibition is the basis of shyness, introversion, and timidity. Kagan believes that timidity is a genetic disposition, although learning and thought affect its expression. There is in fact considerable evidence indicating that anxiety is in part genetically inherited. For example, one study found that the level of anxiety was much more similar in identical twins than in nonidentical twins (in technical terms, the concordance scores for generalized anxiety were 65 percent in monozygotic twins and 13 percent in dizygotic twins). The upshot is that anxiety is closely related to arousal, and different people have different levels of arousal and anxiety, due in part to how sensitive their emotional or arousal systems are.

Is the feeling of anxiety just a more extreme form of arousal? Probably not. A variety of evidence indicates that positive and negative emotions are entirely different systems. Psychologists analyzing what people say about their emotions have concluded that positive and negative emotions constitute two different dimensions of feeling. There is also evidence from the emotional effects of drugs. Anxiety can be effectively treated by benzodiazepines and related drugs, but these drugs have no effect on arousal or alertness. This suggests that anxiety is not simply an excessive level of arousal. However, it remains true that excessive arousal often causes anxiety, and there is a close relation between these two states.


How does body or mind energy relate to feeling energetic or tired? Does the feeling of being energetic actually correspond to the body or brain’s having more energy? We might know everything there is to know about the mechanics of energy supply in body and brain, but this knowledge will be useless unless it can affect our feelings of energy, arousal, tiredness, and fatigue. This is important because if we knew what feelings of energy and tensions corresponded to in the body and brain, we would be better able to interpret the messages they convey and combat them better. In this section we look at this extremely practical but apparently nebulous subject of everyday emotions and moods. Recent psychological research has indicated that feelings of energy or tiredness are central to everyday moods and has come up with some very practical ways of regulating our psychological energy level.

Robert Thayer, professor of Psychology at California State University, has analyzed the origin of everyday feelings of energy, tension, and stress simply by asking people to rate whether they feel energetic or tense in different circumstances. He distinguishes four basic moods that we encounter every day: calm-energy, calm-tiredness, tense-energy, and tense-tiredness. Calm-energy is the ideal, good mood; we feel energetic and aroused, with no tension or anxiety. Calm-tiredness is how we might feel after exercise or before going to bed—tired but relaxed. Tense-energy is how we might feel working on an important project—aroused and full of energy but with some anxiety or edge. Some people (type A personalities and adrenaline junkies) find this mood pleasurable and seek it out in dangerous pursuits, exciting films, or hard business. Tense-tiredness is the classic bad mood; we are anxious or stressed, and without the energy to deal with it. Young children at the end of the day before dinner often end up in this mood, and they cry or throw tantrums. Adults in the same situation are susceptible to anger, arguments, pessimistic thoughts, and depression.

We are most likely to fall into a tense-tired (that is, bad) mood when a stressful situation coincides with a low-energy phase of the day. We may be overly optimistic during our energy peaks and overly pessimistic during our energy troughs.

What determines how energetic we feel? Thayer has identified a number of crucial factors. First, there is a daily rhythm of energy. By asking people to rate how energetic they feel on a scale of one to five at different times of day, and averaging the results over a number of days, Thayer has found a basic energy cycle. People generally feel low in energy when they get up in the morning, but feelings of energy increase continuously until a peak during late morning. Energy then generally dips during mid-to late afternoon and peaks again in early evening before declining to a minimum before going to bed. Of course, not everybody has the same rhythm; some of us are morning people and others evening or night owls. But generally the basic rhythm means that we are best able to cope with difficult situations in the late morning or early evening and least able to cope in the early morning, late evening, and mid- to late afternoon. We are most likely to fall into a tense-tired (that is, bad) mood when a stressful situation coincides with a low-energy phase of the day. We may be overly optimistic during our energy peaks and overly pessimistic during our energy troughs. Thus, Thayer recommends getting to know your own daily energy cycle and assessing your thoughts, feelings, relationships, and decisions in terms of where you think you are in the energy-tiredness dimension.

Another important factor that influences how energetic we feel is exercise. Here we need to distinguish between short- and long-term effects. Thayer has found that if people take a brisk walk for as little as ten minutes, they immediately report feeling more energetic, and this energizing effect lasts for at least one hour after the exercise has finished. This is a dramatic effect that anyone can easily self-administer to increase their energy levels. This immediate mood effect of low-level exercise is rather different from the consequences of intense or long-term exercise. Half an hour of aerobic exercise results in a feeling of fatigue immediately afterward, but often substantially increases the feeling of energy an hour or so later. A long-term exercise program, which increases fitness level, also causes a long-term increase in how energetic we feel. Exercise is also one of the most effective treatments for depression and anxiety. A large number of studies have shown that an exercise program decreases clinical depression and is as effective as a psychotherapy program. Similarly a number of studies have shown that exercise decreases both acute and chronic anxiety. If we also take into account the physical health benefits, exercise would seem to be a panacea. Unfortunately the motivation to exercise is often lacking.

Food probably has a significant effect on our subjective feelings of energy, although there is little scientific evidence linking food to mood, except in relatively extreme conditions. Semi-starvation has been shown to cause chronic feelings of tiredness in a controlled study on conscientious objectors during World War II, and there have been similar findings on famine victims. Low blood sugar level causes tense-tiredness in people, such as diabetics, who cannot control their blood sugar level properly. Whether this occurs in ordinary people—after missing a meal, for example—has been more difficult to prove, although there is circumstantial evidence for a mild increase in tense-tiredness. Certainly most people believe that fasting causes tiredness or tension (or both) and that food reverses these feelings, and this may be an important motivation for eating or snacking. Thayer has studied the mood effects that people report after eating a candy bar (that is, a high-sugar bar, such as a chocolate bar), averaged over a large number of such occasions. Immediately after eating the bar, subjective feelings of energy increased as expected, but an hour later, energy dropped to levels below those before eating the bar, and there was an increased feeling of tension. The immediate energizing property of high-sugar snacks or drinks may be what motivates us to use them when we are feeling tired. However, we need to recognize that beyond the immediate positive response may lurk the medium-term energy-draining effect of sugar. A heavy meal makes many people feel drowsy, and obese people often report feeling tired. The multiple effects of food on mood are obviously complex and difficult to disentangle.

The impact of illness on energy is more clear-cut. Healthy people feel more energetic than sick people. Many surveys have shown that the most common complaint and symptom reported to doctors is fatigue and lack of energy. For example, one study of five hundred medical patients seen in a general health center in the Boston area found that 37 percent reported feeling very tired, often for months before seeking treatment. People who feel energetic generally are healthy, whereas people who feel tired all the time often are ill or will be ill soon. Many different illnesses lead to decreased feelings of energy. Jane Dixon and colleagues at Yale University assessed the health status and mood of more than three hundred nurses and found that reported energy level had the highest correlation with general health status. Moreover, energy was the best predictor of both physical and psychological health over time. Thus, feelings of energy may act as both a symptom of present health and a predictor of future health or illness.

Sleep, or lack of it, obviously affects how energetic we feel. Our need for sleep follows a daily cycle, which matches the daily cycle of our feelings of energy. This endogenous cycle becomes obvious if we abruptly change the time at which we sleep, as when we jet across several time zones. This results in jet lag as our endogenous body clock continues to generate a twenty-four-hour cycle of energy followed by tiredness that does not coincide with the day and night of our new location. Sleep disorders and sleep deprivation can also cause fatigue. Research has suggested that up to one-third of Americans may be suffering from sleep disorders, causing significant daytime tiredness.

There may be a seasonal cycle of energy, although there is no direct evidence for this in the general population. However, some researchers believe that 5 percent or more of the population suffer from seasonal affective disorder (SAD), a moderately debilitating form of depression, usually occurring during the winter months, characterized by inactivity, anxiety, weight gain, carbohydrate craving, increased sleep, and sleepiness, and decreased libido. SAD can be treated by light, and this has led to the theory that the disorder is due to light starvation during the winter months and may, in turn, affect the secretion of melatonin within the brain. Melatonin is a brain hormone secreted mainly in the dark and regulates the sleep-waking cycle. However, there are many other theories to explain SAD, and it is still not clear whether SAD is a real disorder or a medical artifact. 

Many people report using social interaction to regulate their own mood; that is, if they are feeling tense or low in energy, they will phone or visit other people in order to improve their mood.

Various other factors influence perceived levels of energy, including social interaction and drugs. Many people report using social interaction to regulate their own mood; that is, if they are feeling tense or low in energy, they will phone or visit other people in order to improve their mood. And indeed a number of studies have shown that this can be a successful strategy for improving mood, and, further, that people who have a high level of social interaction generally have a positive mood. On the other hand, it seems unlikely that people who are depressed, anxious, or socially introverted would automatically benefit from increased social interaction. Caffeine, nicotine, cocaine, and amphetamine all increase subjective feelings of energy, and many people use them, consciously or unconsciously, to regulate their energy level. However, energy levels decline below normal levels after use, and repeated use requires higher and higher levels to get the same effect.

Finally, we should note Thayer’s finding that people’s judgment of their energy level affects both what they choose to do in the present and their assessment of their capacity to do things in the future. Thus we adjust the tasks we are doing depending on how much physical or mental energy we think we have. When we are getting sluggish during the day or tired at night, we switch to less demanding activities, such as chatting to friends, watching television, or listening to music. If we are mentally fatigued but unable to switch from a task that requires a lot of energy—for example, we have to meet a deadline at work—then inevitably the sympathetic nervous system will be stimulated, leading to an increased supply of energy but also a feeling of tension and anxiety. In such circumstances we may seek out sugar, caffeine, or nicotine to boost our energy levels; these remedies, however, will cause a medium to long-term drop in energy levels, so we may be better off taking a brisk ten-minute walk. When in an energetic mood, we may project this assessment of our capacities into the future and commit ourselves to tasks that we may have insufficient energy to fulfill. For example, in a good mood, we may say we will take on some commitment or relationship, start some exercise program, stop some bad habit, or go to some party, but we may be overly optimistic about how much mental and emotional energy we will have at the time that these commitments must be fulfilled. By contrast, when we are low in energy or depressed, we may shy away from any commitment in the future requiring physical, mental, or emotional energy. In this case, we may be overly pessimistic about our future capacities, potentially leading to a downward spiral in the quantity and quality of our activities. The solution, according to Thayer, is to gain an awareness of our own mood cycles and to make a realistic assessment of our future capacities not solely based on our present mood.


Your hypothalamus is located just above the roof of your mouth. The multiple smudges of neurons that make up the hypothalamus lie on either side of a dark, water-filled lake, the third ventricle, within which in classical times the animal spirits were thought to swim. The hypothalamus is the drive center of the brain, controlling hunger, thirst, lust, anger, and arousal. But it does not arbitrarily evoke these passions like some idiosyncratic Greek god. Rather the hypothalamus is like Blake’s vision of Isaac Newton as a cold scientist, measuring and taking the measure of everything, and calculating how much “what is” deviates from “what is desired” and then producing an appropriate amount of drive to correct that gap between “how things are” and “how things should be.” The hypothalamus does indeed take the measure of almost everything occurring in the body and mind: it measures the food, fuel, salt, and water content of the body by monitoring the contents of the blood as it passes through the hypothalamus. It compares these values with some predefined target values, and it adjusts the drives of hunger and thirst in order to nudge the real values closer to the target values. It measures the temperature of the body, and like a thermostat on a central heating system, it sends messages to regulate the heat production or dissipation of the body appropriately. The thermostat can be adjusted slightly by conditions like illness; hence, body temperature can be increased in fever, because the hypothalamus also monitors illness via chemicals released by the immune system. The hypothalamus contains a clock, the body clock, to keep track of what time of day it is, and it adjusts our level of arousal and our sleep-wake cycle to keep time with this clock. 

The hypothalamus does not just monitor what is going on in the body; it also keeps track of the mind. In particular, it is connected to the emotional centers of the brain, which surround it like a pair of hands in which it is cradled. The hypothalamus sees the world through this fog of emotion. Sensory information from the eyes, ears, and body passes through the thalamus at the center of the brain and then either goes on up to the rational mind, in the cerebral cortex on the surface of the brain, or to the emotional mind, which surrounds the core of the brain. Within the emotional centers (which used to be called the limbic system), the sensory information is compared to emotional memory in order to determine whether it has any relevant emotional content, such as “scary,” “scrumptious,” or “sexy.” This emotional labeling often requires the help of the rational mind, so there may be a lot of to and fro of information before a label is settled on, although if rapid action is required, the emotional centers can decide for themselves. If the body and mind need to be alerted and aroused—for example, if the emotional centers perceive a dangerous threat —then the hypothalamus is activated to raise the alarm via the ANS in the body and the RAS in the brain. In a sense, the hypothalamus works by monitoring the emotional tone of the brain, just as it monitors the physical tone of the body, and it acts to correct any deviations from the norm by sending signals to other areas of the brain. The hypothalamus is the drive center of the brain, managing all the passions, but these passions are not blind.

About Cerebrum

Bill Glovin, editor
Carolyn Asbury, Ph.D., consultant

Scientific Advisory Board
Joseph T. Coyle, M.D., Harvard Medical School
Kay Redfield Jamison, Ph.D., The Johns Hopkins University School of Medicine
Pierre J. Magistretti, M.D., Ph.D., University of Lausanne Medical School and Hospital
Helen Mayberg, M.D., Icahn School of Medicine at Mount Sinai 
Bruce S. McEwen, Ph.D., The Rockefeller University
Donald Price, M.D., The Johns Hopkins University School of Medicine
Charles Zorumski, M.D., Washington University School of Medicine

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