Friday, December 15, 2006

Hardwired for Happiness

By: Silvia Helena Cardoso , Ph.D.

Happiness, which is good for both mind and body, is at least in part biological, rooted in the evolution of the brain and nervous system.

The pursuit of happiness is the engine that moves humankind, that motivates us to study, to work, to marry and have children, to make friends, to pursue all sorts of worldly pleasures, to dream of the future, and sometimes to fight for social and financial status. Of all the goals we may pursue in life, happiness is the only one to have worth in itself; all the others—health, power, money, beauty, success—make sense only as means of achieving it. To many people, life would be unbearable without the belief that they can be happy.

Are our brains “hardwired” for happiness? That is, does happiness have a biological basis, rooted in the evolution of the nervous system? If so, understanding how our brain machinery works to make us happy could suggest ways to transform our behavior and our relationships with others, as well as to set up a better society.

Of course, to define happiness objectively is difficult.  Joseph Ledoux, Ph.D., the well-known researcher and author on the physiology of emotions, expressed the scientist’s frustrations with this elusive entity well when he wrote: “There are many answers for what are emotions/happiness. Many of them are surprisingly unclear and ill-defined.”  Neuroscientist Richard J. Davidson, Ph.D., observed that the word happiness “is a kind of a placeholder for a constellation of positive emotional states. Of all the emotions, happiness is the one scientists least understand.”

Studying the many enemies of happiness, such as stress, depression, anxiety, and phobias, is essential, of course, but recently researchers have turned their attention to the brains of happy people as well. Even though scientists still do not agree on the precise definition of happiness, they are beginning to discover a vast array of biological counterparts to what we associate with the idea of happiness. Functional imaging methods and the study of key neurotransmitters in the mechanisms of emotion in the brain and body have led not only to a deeper understanding of the biological components of happiness but also to practical applications for achieving it, such as antidepressant drugs. 

Searching for Happiness in the Brain

Neuroscience, biology, and psychology all have important roles in deciphering and elucidating the mechanisms and purpose of positive emotions. Great scientists, from Charles Darwin to William James to Sigmund Freud, have studied in detail our most basic negative emotional processes, such as fear, stress, anxiety, anger, and aggression, and how they relate to the brain, nervous system, hormones, and internal organs. Their findings provided most of the knowledge we have today about the neural correlates of emotion in general, particularly the role of subcortical structures such as the limbic system, hypothalamus, thalamus, basal ganglia, and midbrain.

Positive emotions, however, used to be considered too subjective and difficult to study, so for a long time neuroscientists neglected them. Unhappiness was considered to arrive on its own, since fear, anger, and defense are responses to danger from the external world and are vital for our survival (“fight or flight”). But our feelings of pleasure and happiness were thought to be largely cultural and were regarded only as guiding our behavior toward desirable situations.  

In the middle of twentieth century, however, new approaches and techniques for investigating the nervous system began to provide more rigorous ways to evaluate positive affective (that is, mood) states. The first real breakthrough came in the 1950s, when American psychologists James Olds, Ph.D., and Peter Milner, Ph.D., discovered what they named the “pleasure centers in the brain.”1 Rats that were implanted with electrodes in certain areas of the brain learned to press a lever that would deliver pulses of electrical stimulation to these areas. Most of the experimental animals were so taken by the stimulation effects that they would not even stop to eat, drink, or rest, but would press the lever at fantastic rates until they were totally exhausted. They would even cross electrified grids to reach the lever.

The phenomenon of self-stimulation of the brain occurred only in certain parts of the subcortical brain, not in others, showing that specific structures processed motivational input; the nucleus accumbens was one of the most active.  Stimulation of the nucleus accumbens in humans elicits smiling, laughter, pleasurable feelings, happiness, even euphoria. Extensive mapping proved the existence of a coherent “reward system” in the brain, which was also shown to exist in many mammals, including humans.  As shown in the figure below, when the cortex has received and processed a sensory stimulus indicating a reward, it sends a signal to the ventral tegmental area (VTA) in the midbrain. The VTA then releases dopamine not only into the nucleus accumbens, but also into the septum, the amygdala, and the prefrontal cortex.  These regions are connected through the medial forebrain bundle (MFB).

brain reward circuit 
 The Reward Circuit 

Credit: The Brain From Top to Bottom, Canadian Institutes of Health Research

What is the secret to the behavior elicited by stimulation of the nucleus accumbens? The answer is dopamine, which is involved in functions ranging from motivation and reward to feeding and drug addiction. Dopamine is a neurotransmitter, a chemical substance released by neurons at their synaptic connections to other neurons in the brain. The first neurotransmitter to be associated with positive emotions and feelings, it is essential for activation of the reward system because it sets in motion the neural circuits involved in motivation. The dopamine-driven reward system is best known for its association with addiction, in which it causes uncontrollable urges to engage in a destructive behavior.

According to neuroscientist Kay Jamison, Ph.D., author of Exuberance: The Passion for Life (Vintage Press, 2005), dopamine transmission in the brain may also be related to the exuberant temperament, as well as to the mania, of bipolar disorder (also known as manic-depression). When asked whether there is a clear dividing line between exuberance and mania, Jamison said, “Exuberance can escalate into mania in people who are predisposed to manic-depressive or bipolar illness. Most exuberant people never become manic, but those who have bipolar illness often have an exuberant temperament.”

A second breakthrough in understanding the neural basis of positive emotions came in the 1970s, when American neuroscientists Solomon H. Snyder, M.D., and Candace Pert, Ph.D., discovered that our brains produce endorphins, a kind of internal morphine composed of a sequence of amino acids. Receptors for endorphins, called opiate receptors, can be found in several parts of the brain. When released by the pituitary gland and by neurons in the hypothalamus, endorphins suppress pain. In addition, pleasurable feelings that accompany actions such as eating chocolate, laughing, smiling, touching, meditating, singing, listening to good music, and even orgasm are partially attributed to the brain’s release of endorphins.

Endorphins released in the brain also increase the release of dopamine.  As proposed by neuroscientist Kent Berridge, Ph.D., at the University of Michigan, wanting (desire) and liking (pleasure) appear to be two distinct biological processes with separate but interrelated neurochemical systems in the brain, both related to positive emotions, including happiness.2 Although many gaps in the scientific knowledge remain to be filled, Pert went on to propose that opiate receptors and endorphins provide a biomolecular basis for emotion and are the key to the effect of emotions on our health.3

What Brain Imaging Shows

The fantastic progress in techniques for obtaining functional images of the brain—color images that reveal precisely what brain structures are activated and deactivated when certain emotions or behaviors occur in human beings—has had a major impact on neuropsychology in the last decade. These images allow us to study the brain basis of emotions in a non-invasive way, without having to intervene in the brain as scientists do with experimental animals, for example by implanting electrodes or creating lesions.

In the 1990s, Antonio Damasio, M.D., Ph.D., discovered that positive and negative feelings are both generated and processed by different parts of the human brain. Damasio and his group at the University of Iowa were among the first to use positron emission tomography (PET) to map the brain correlates of emotions, both negative and positive.4 The researchers, who took PET scans of brain activation while volunteers made themselves feel anger, fear, sadness, andAs various biochemicals act on the neural circuits of our hearts, we discern different patterns and strengths of heartbeats, which lead us to feel, variously, contentment, happiness, love, joy, despair, depression, fear, or anger. happiness, made several interesting discoveries. First, different emotions activate or deactivate different areas of the brain. Happiness, for instance, had a functional pattern remarkably distinct from sadness, sometimes in opposite ways. Second, the activation and deactivation patterns exhibited marked asymmetries; that is, the two sides of the brain reacted differently to the induced emotions. Happiness activated the right posterior cingular gyrus, as well as the left insula and the right secondary sensorimotor cortex. Sadness, as one would expect, decreased activation in these regions. Other structures in the basal region of the brain, such as the pons, were activated in sadness but not in happiness.

Damasio proposed a distinction between emotions and feelings. According to his “somatic marker hypothesis,” the sensory system detects peripheral changes in the heart, circulatory system, skin, and muscles that are commanded by emotions in the brain and interprets these changes as feelings.5 This could explain why Aristotle considered that the heart was the seat of the soul and emotions, something we still see in our everyday language and symbols—for example, the universal sign of love is a heart. As various biochemicals act on the neural circuits of our hearts, we discern different patterns and strengths of heartbeats, which lead us to feel, variously, contentment, happiness, love, joy, despair, depression, fear, or anger. The heaviness of heart we feel in an amorous deception is quite different from the flutter of passion.

The brain processes involved in voluntary control of negative emotions, which enables normal, healthy people to resist sadness and depression, were demonstrated by a group of neuroscientists from Montreal, Canada.6 They studied functional brain images of people induced to feel sadness by watching short films and those of people who were able to suppress this feeling by an internal effort. The study showed that sadness caused changes in the right ventrolateral prefrontal cortex, the anterior temporopolar cortex, the affective division of the cingular cortex, and the insula (all regions that have been previously associated with human emotional regulation). On the other hand, the voluntary suppression of sadness activated the right dorsolateral prefrontal cortex and the right orbitofrontal cortex.

Note the role of the right hemisphere in connection with negative feelings, and the role of the prefrontal cortex in processing basic emotions. The ventrolateral prefrontal cortex  in particular seems to be part of the circuits processing information from the body when activated by emotion. So it might be involved in the somatic marker system proposed by Damasio. The role of the dorsolateral prefrontal cortex in suppressing sadness that was observed in the Montreal study agrees with previous studies showing that it is also involved in the willed suppression of positive emotions, sexual arousal, and other feelings. This part of the brain seems to be related to holding information in temporary memory. We might speculate whether the right dorsolateral prefrontal cortex could be trained to suppress negative emotions and thus make people happier.

An explosion of imaging studies of emotions followed the development of functional magnetic resonance imaging (fMRI), which is easier to use than PET.  For many, the abundance of results seemed to conflict with each other and muddled considerably any effort to find a single cohesive interpretation. A recent survey of 106 studies,7 for example, could not determine a concordance of activated areas for happiness and sadness that was as clear-cut as the initial studies by Damasio. Other areas that appeared regularly in most of the imaging studies of happiness were the rostral supracallosal anterior cingulate cortex and the dorsomedial prefrontal cortex. Many studies have associated the anterior cingulate cortex with the regulation of emotions, so it has been named “the affective division” of the cingulate cortex. It also appears to be altered in people with depression, for whom happiness is difficult to achieve.

Also, Richard J. Davidson, Ph.D., and his group at the University of Wisconsin reported activation of the left frontal part of the brain while study participants watched happy video clips, as well as when Buddhists were meditating.8   Many studies have observed important functional differences between the left and right sides of the prefrontal cortex. The left side seems in general to be associated with positive emotions (lesions in this side of the brain cause depression), while the right side is associated with negative emotions.

Most of the studies reported so far seem to support a theory of emotions that applies to happiness: the “central affect program.” Although first proposed by Charles Darwin in his 1872 book The Expression of the Emotions in Man and Happiness is both a general state of being and the result of specific time-delimited events. Animals, the current description of this theory has been championed by noted emotion researchers such as Paul Ekman, Ph.D.,9 and Jaak Panksepp, Ph.D.10 According to this theory, an affect program is a brain mechanism that stores patterns for and triggers complex stereotyped emotional responses, which are present in the same form in all humans and cultures. Specific affect programs are controlled by interconnected brain structures and develop over time.

Recent imaging studies have given credence to this theory, because the activation of discrete brain regions has been correlated with specific emotions, such as activation of the amygdala by fear. A clearer definition of happiness and better research methods, particularly for inducing the feeling of happiness under laboratory conditions, are necessary, but functional neuroimaging holds great potential for non-invasive studies of the happy brain in operation. 

The Set Point for Happiness

Happiness is both a general state of being and the result of specific time-delimited events. Psychologists have established that each person has an average overall level of happiness at any particular period of life. When you ask someone whether he is happy, he usually answers quickly and with assurance, reflecting his appraisal of the average during a relatively recent period. This average state, or baseline, has been defined by researchers such as David Lykken, Ph.D., as a “set point” of happiness,11 in the same way that a stable level of glucose concentration in the blood is set by the body or the temperature is set for a refrigerator.

Different people have different set points of happiness. Discrete events, such as the day you marry or have your first child, or when one of your parents dies or you are fired from your job, cause a sudden temporary increase or decrease in your level of happiness. But most people almost invariably return to their set points at some time after the especially happy or unhappy event. Moreover, the set  point is normally above neutral—most people lean more toward being happy than unhappy—and unhappy events have less influence and are more quickly forgotten than happy ones.

The general set point of happiness can be modified downward by chronic disturbances, such as depression, or upward by medication. Some antidepressant drugs, for example the serotonin reuptake inhibitor fluoxetine (Prozac), actually seem to be able to alter the set point in some people, leading to such drugs’ being dubbed “personality cosmetics” and “happy pills.” Cognitive behavioral therapy may also have this power.

Just as one cannot be unhappy all the time and be considered healthy, one cannot be euphoric (euphoria means an excess of happiness) or exuberant all the time (exuberant means excessively enthusiastic). A healthy person will soon return to normal, previous levels of happiness. In fact, excessive, out-of-context euphoria and exuberance are hallmarks of pathological conditions, such as hypomania and the manic phase of bipolar disorder. Kay Jamison observes, “In their mild forms exuberant states are intoxicating and adaptive but in their extremes they are pathological; in short, exuberance can range from imagination and exploration to recklessness and madness.”

The observation that happiness is a fluctuating state with a set point suggests the hypothesis that it is regulated internally, as are other basic organic and mental states, by homeostatic mechanisms, which control dynamic adjustments to maintain a stable condition. As the saying goes, “Time is the best healer.” In other words, the homeostatic mechanism returning one to one’s normal level of happiness eventually prevails. 

Evidence from Evolution

All anatomical and physiological characteristics of human beings were molded by natural selection. Emotions are primitive components of human behavior that are processed by older parts of our brain, such as the limbic system, the Because happiness is a positive emotion, we can hypothesize that it acts as a good motivator and internal reinforcer of behavior, particularly for achieving long-range goals that are important for the survival of the organism or species. hypothalamus, and the brain stem. According to Norwegian biologist Bjorn Grinde, D.Sc., D.Phil., the human capacity for positive and negative feelings was shaped by the forces of evolution, so the evolutionary perspective should be relevant to the study of happiness. The evolutionary perspective has four important correlates.

First, because we share basic emotions and their neural substrates with other mammals and non-human primates, in theory a predecessor for happiness should exist in animals. Some ethologists agree that chimpanzee behavior, observed both in the wild and in captivity, suggests that an internal state analogous to human happiness can be found in these animals.

Second, happiness should be represented in the brain in the form of hardwired circuits; otherwise, it could not be selected during evolution. We have examined some of the evidence that points to this, and I think that eventually objective neuroscientific studies will confirm that this is exactly the case.

Third, a set of genes and a mechanism for genetic expression are needed in order to construct specific brain circuits.  David Lykken (who first proposed the idea of a happiness set point) was also responsible for research that has provided the strongest evidence so far for a genetic basis for happiness. In a study of identical twins separated at birth, some 60 percent of the likelihood that each twin would describe himself or herself as happy was accounted for by common genetic factors, not by environmental differences in their lives.  Lykken argues that “the laws governing happiness were designed not for our psychological well-being but for our genes’ long-term survival prospects.”

Finally, to support the evolutionary perspective, happiness should have a direct or indirect value for the survival of its controlling genes. Because happiness is a positive emotion, we can hypothesize that it acts as a good motivator and internal reinforcer of behavior, particularly for achieving long-range goals that are important for the survival of the organism or species. One of the leading researchers on the brain structures related to motivation, Larry Swanson, Ph.D., has found growing evidence that the brain is hardwired for happiness via goal-seeking behavior.12 He says: “Setting and achieving goals can have an amazing influence on creating well-being in our daily lives and making us feel happy. This is because the steps involved in goal-directed activity, namely motivation, goal seeking, successful outcome, and feelings of pleasure, are wired into the brain’s structure.”

A behavioral chain composed of tens of thousands of individual acts (such as those necessary, for instance, for graduating with a medical degree many years after you initially wanted to become a doctor) must be somehow reinforced along the way, and happiness is a good candidate to be that reinforcer. A hunting, bipedal hominid would need not only motivation but continual reinforcement in order to plan and execute the long chain of behaviors that would lead eventually to his presentation of a carcass of meat to his family for their survival. So every step, such as preparing the weapons, running through the hunting grounds, planning the kill, and felling the prey, would generate some combination of enthusiasm, determination, hope, joy, and contentment, all components of what we call happiness.

Going further, many psychologists have proposed a hierarchy of needs. Some needs are more important than others, but happiness is associated with fulfillment at all levels.  The best-known schema, created by Abraham Maslow, Ph.D., is set up as a conceptual pyramid. Needs must be satisfied in order of priority: first the physiological needs (food, water, rest) and safety (shelter, protection against enemies and dangers); then love and belongingness (for example, the search for positive affect, social participation); esteem (self-esteem and the search for the respect of others); and, finally, self-fulfillment (self-sufficiency, vitality, creativity, meaningfulness, and so on).

Hierarchy of Needs 
 Maslow’s Hierarchy of Needs

Credit:  J. Finkelstein/Wikipedia

As with other primitive emotional components of our minds, such as fear or anger, over the course of evolution happiness has become a dominating feature of many aspects of our life. While neuroscientists have not yet agreed on all of the critical brain regions and processes that underlie it, happiness seems to be at least partly determined by hardwired, genetically expressed structures in our brains. For human beings, happiness is a complex mix of nature (hardware) and nurture (software), greatly influenced and modified by cultural experiences and learning. 

Toward a Definition of Happiness

Drawing together what science has learned about the biological basis for positive emotions such as happiness, we can begin to move toward a definition against which future research discoveries can be measured. I suggest that happiness involves:

  • a general average level of contentment and well-being,  with a high frequency of positive feelings such as good humor, joy, laughter, hope, and enthusiasm, coupled with relative freedom from negative feelings such as sadness, worry, anxiety, anger, irritability, despondency, and despair;
  • the presence of more positive (happy) than negative (unhappy) events in our lives, and, more important, the ability, when negative feelings occur, to allow them only a minimal effect on our emotions (and on our bodies as well);
  • a personality (both genetically and culturally determined), an individual disposition, and behavioral traits that make a person more resilient to adversity and more prone to enthusiasm, laughter, and good humor;
  • a match between our life expectations and our deeds. Aristotle wrote that “happiness is the consequence of a deed”—that is, it is the result not of chance but of using for the best all the opportunities that we encounter in our lives.

Helping Happiness Prevail

People need to be happy in order to build a satisfying world and thrive in it. Our own nature will then reward us with its best—inner peace, pleasure, and joy.  But unfortunately what human nature gives, it also takes back rather quickly. After our moments of bliss, back we go to our previous level of happiness, our set point. This oscillation appears to be the way of life, but a more enduring state of happiness is possible if we persist in helping our positive emotions to prevail.

Science has shown again and again that being happy is good for your mind and your body. Happy people are more confident, optimistic, energetic, and sociable. They are also better prepared to deal with difficult situations, are more enjoyable to live and to work with, and have a higher capacity for pursuing their aims and acquiring the means to achieve them. In addition, happy people appear to be healthier and live longer. For instance, just recently Sheldon Cohen, Ph.D., of Carnegie Mellon University published a study confirming his earlier discovery that people who are happy or exhibit other positive emotions are less likely to become ill when they are exposed to a cold virus and, when they do catch a cold, they have fewer symptoms.

For much of humankind, getting enough sustenance for physiological needs, survival, and safety is a constant battle, which many, unfortunately, lose. Satisfying even these most basic needs requires the joint work of emotions and Although we cannot change our genetic makeup or our individual past, science has developed many ways of correcting and even healing detrimental influences of those factors on happiness. cognition, of subcortical as well as neocortical brain systems, all acting under the command of our prefrontal brain, the jewel of human evolution. Those of us who are more fortunate, however, can seek to reach other levels of Maslow’s pyramid of human needs, such as achieving self-esteem, self-actualization, authenticity, and meaningfulness. Such continuous growth seems to be an important ingredient of a happy life.

Research in psychology has shown repeatedly that the ability to regulate one’s emotions is essential for a happy life. While we may strive to be rational and in control, emotions are an indissoluble and essential part of our psyche. The great personal search, then, is how to defeat our inner enemies, to achieve control over our negative emotions. Although many psychologists and neuroscientists decry as unsupported sensationalism what has been known as the “power of positive thinking,” in fact several serious studies, using functional brain imaging techniques to observe the brain during sadness and happiness, have shown that distinct parts of the prefrontal cortex are involved in the volitional suppression of negative feelings.

The effectiveness of cognitive behavioral therapy in dissipating automatic negative thoughts and feelings has demonstrated that achieving happiness by self-control is not impossible. Relaxation and meditation techniques, originally developed by philosophies and religions of the Far East, have also proved helpful in increasing positive emotions and controlling negative ones. Neuroimaging research has shown that meditation is accompanied by a clear increase of activity in the left prefrontal cortex, known to be related to positive emotions, and a decrease of activity in the parietal cortex, related to spatial localization (thus facilitating the meditator’s becoming more concentrated on his inner self). Equally effective for many people are techniques used to activate the brain’s reward systems and increase levels of dopamine, serotonin, and endorphins through pleasurable sensations such as music, light, color, and touch.

Of course, we should not forget that mind power is not enough. Individual propensity for happiness also depends on our genetic heritage (more than 60 percent, according to studies with twins). Both innate temperament and negative early experiences in life, such as traumatic stress and abuse, are extremely influential. Fortunately, however, we can end this article on an optimistic note. Although we cannot change our genetic makeup or our individual past, science has developed many ways of correcting and even healing detrimental influences of those factors on happiness. And we are certain that the future will provide an even greater and more impressive set of techniques and tools to help us look inside the happy brain and, as a result, discover more ways in which people can claim their own happiness.

References

1. Olds, J, and Milner, P. Positive Reinforcement Produced by Electrical Stimulation of the Septal Area and Other Regions of the Rat Brain. Journal of Comparative and Physiological Psychology 1954; 47: 419–428. 

2. Berridge, KC. Motivation Concepts in Behavioral Neuroscience. Physiology and Behavior 2004; 81(2): 179–209. 

3. Pert, C. Molecules of Emotion: The Science Behind Mind-Body Medicine. New York. Scribner, 1999. 

4. Damasio, AR, Grabowski, TJ, Bechara, A, Damasio, H, Ponto, LL, Parvizi, J, and Hichwa, RD. Subcortical and Cortical Brain Activity During the Feeling of Self-Generated Emotions. Nature Neuroscience 2000; 3: 1049–1056. 

5. Damasio, A. Feeling of What Happens: Body, Emotion, and the Making of Consciousness. London. Heinemann, 1999. 

6. Levesque, J Eugene F, Joanette, Y, Paquette, V, Mensour, B, Beaudoin, G, Leroux, J-M, Bourgouin, P, and Beauregard, M.. Neural Circuitry Underlying Voluntary Suppression of Sadness.  Biological Psychiatry 2003; 53: 502–510. 

7. Murphy, FC, Nimmo-Smith, I, and Lawrence, AD. Functional Neuroanatomy of Emotions: A Meta-analysis. Cognitive, Affective, and Behavioral Neuroscience 2003; 3(3): 207–233. 

8. Davidson, RJ. Toward a Biology of Personality and Emotion. Annals of the New York Academy of Sciences 2001; 935: 191–207. 

9. Ekman, P. Basic Emotions. In T Dalgleish and MJ Power (Eds.), Handbook of Cognition and Emotion. Chichester, UK. Wiley, 1999: 45–60. 

10. Panksepp, J. Emotions as Natural Kinds Within the Mammalian Brain. In M Lewis and JM Haviland-Jones (Eds.), Handbook of Emotions. New York. Guilford, 2000: 2nd ed., 137–156. 

11. Lykken, D. Happiness: The Nature and Nurture of Joy and Contentment. New York. St. Martin’s Griffin, 2000.



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
Robert Malenka, M.D., Ph.D., Stanford University School of Medicine
Bruce S. McEwen, Ph.D., The Rockefeller University
Donald Price, M.D., The Johns Hopkins University School of Medicine

Do you have a comment or question about something you've read in CerebrumContact Cerebrum Now.