The brain is the mind is the brain. One hundred billion nerve cells, give or take, none of which individually has the capacity to feel or to reason, yet together generating consciousness. For about 400 years, following the ideas of French philosopher René Descartes, those who thought about its nature considered the mind related to the body, but separate from it. In this model—often called "dualism" or the mind-body problem—the mind was "immaterial," not anchored in anything physical. Today neuroscientists are finding abundant evidence of an idea that even Freud played with more than 100 years ago, that separating mind from brain makes no sense. Nobel Prize-winning psychiatrist-neuroscientist Eric Kandel stated it directly in a watershed paper published in 1998: "All mental processes, even the most complex psychological processes, derive from operations of the brain."
Neuroscientists consider it settled that the mind arises from the cooperation of billions of interconnected cells that, individually, are no smarter than amoebae. But it's a shocking idea to some that the human mind could arise out of such an array of mindlessness. Many express amazement that emotions, pain, sexual feelings or religious belief could be a product of brain function. They are put off by the notion that such rich experiences could be reduced to mechanical or chemical bits. Or they worry that scientific explanations may seduce people into a kind of moral laziness that provides a ready excuse for any human failing: "My brain made me do it." Our brains indeed do make us do it, but that is nonetheless consistent with meaningful lives and moral choices. Writing for the President's Council on Bioethics earlier this year, philosopher Daniel Dennett made the point that building knowledge about the biology of mental life may improve our decision making, even our moral decision making. And it could enhance our chances of survival as a species, too.
Your heart, lungs, kidneys and digestive tract keep you alive. But your brain is where you live. The brain is responsible for most of what you care about—language, creativity, imagination, empathy and morality. And it is the repository of all that you feel. The endeavor to discover the biological basis for these complex human experiences has given rise to a relatively new discipline: cognitive neuroscience. It has recently exploded as a field, thanks, in part, to decades of advances in neuroimaging technology that enable us to see the brain at work. As Dr. Joel Yager, professor of psychiatry at the University of Colorado, has said, "We can now watch the mind boggle!"
Certainly, you won't find an entry for "mind-boggling" in the index of a modern neuroscience textbook. You will also have a hard time finding the words "happiness" or "sadness," "anger" or "love." Neuroscientists do, however, have a rapidly growing appreciation of the emotional brain and are beginning to look closely at these subjective states, which were formerly the province of philosophers and poets. It is complex science that holds great promise for improving the quality of life. Fortunately, understanding basic principles does not require an advanced degree.
Fear is a good place to start, because it is one of the emotions that cognitive neuroscientists understand well. It is an unpleasant feeling, but necessary to our survival; humans would not have lasted very long in the wilderness without it. Two deep brain structures called the amygdalae manage the important task of learning and remembering what you should be afraid of.
Each amygdala, a cluster of nerve cells named after its almond shape (from the Greek amugdale), sits under its corresponding temporal lobe on either side of the brain. Like a network hub, it coordinates information from several sources. It collects input from the environment, registers emotional significance and—when necessary—mobilizes a proper response. It gets information about the body's response to the environment (for example, heart rate and blood pressure) from the hypothalamus. It communicates with the reasoning areas in the front of the brain. And it connects with the hippocampus, an important memory center.
The fear system is extraordinarily efficient. It is so efficient that you don't need to consciously register what is happening for the brain to kick off a response. If a car swerves into your lane of traffic, you will feel the fear before you understand it. Signals travel between the amygdala and your crisis system before the visual part of your brain has a chance to "see." Organisms with slower responses probably did not get the opportunity to pass their genetic material along.
Fear is contagious because the amygdala helps people not only recognize fear in the faces of others, but also to automatically scan for it. People or animals with damage to the amygdala lose these skills. Not only is the world more dangerous for them, the texture of life is ironed out; the world seems less compelling to them because their "excitement" anatomy is impaired.
Until recently, there was relatively little research showing how the brain processes anger. But that has begun to change. Recent studies indicate that anger may trigger activity in a part of the brain not named as poetically as the amygdala—the dorsal anterior cingulate cortex (abbreviated dACC). Like the amygdala, the dACC's function makes sense, given its connections to areas of the brain involved in recognizing an offense (he just stole my iPod), registering a feeling (I'm angry) and acting on it (I'm going to …). It also links to the reasoning centers in the front part of the brain, as well as memory centers, which play a role in angry rumination or stewing after the fact.
Researchers, however, have been more focused on one of the consequences of anger—aggression—probably because it can be observed through behavior. It's known, for example, that men are overtly more aggressive than women because of differences in male and female hormones. But the brains of men and women are also different, and some of those differences may affect aggression. In the front of the brain, the orbitofrontal cortex is recruited to help make decisions and temper emotional responses. It lights up when people are making judgments. Adrian Raine and colleagues at the University of Southern California note that, on average, men have a lower volume of gray matter (the bodies of nerve cells) in the orbitofrontal cortex than women. According to their analysis, this brain difference accounts for a healthy portion of the gender gap seen in the frequency of antisocial behavior.
Even a neuroscientist can see that murder and mayhem are undesirable. But a neuroscientist can also see why that trait might still be in the gene pool. The gene for sickle cell anemia survived because it provided protection against another disease, malaria. Similarly, aggression is often an advantage. Until recently in historical terms, a readiness to fight and the ability to kill was a way to consolidate control over resources for survival.
Fortunately, diplomats have also evolved. Some of our ancestors who understood that aggression carried risks as well as advantages used their creative human brains to devise better solutions for resolving conflicts. Our predecessors also originated symbolic diversions for aggression, like sports and chess.
So Happy (and Sad) Together
The common emotions of sadness and happiness are a problem for researchers. Depression and mania are core areas of study for a neuroscientist. But everyday ups and downs are so broadly defined that researchers have a hard time figuring out what exactly to study. They note activity in virtually every part of the brain. Last year Drs. Peter J. Freed and J. John Mann, publishing in The American Journal of Psychiatry, reported on the literature of sadness and the brain. In 22 studies, brain scans were performed on nondepressed but sad volunteers. Sadness was mostly induced (subjects were shown sad pictures or films, asked to remember a sad event), although, in a couple of studies, subjects had recently experienced a loss. In the aggregate, sadness appeared to cause altered activity in more than 70 different brain regions. The amygdala and hippocampus both show up on this list, as do the front part of the brain (prefrontal cortex) and the anterior cingulate cortex. A structure called the insula (which means "island") also appears here—it is a small region of cortex beneath the temporal lobes that registers body perceptions and taste.
The authors believe this complicated picture makes sense. The brain regions on their list process conflict, pain, social isolation, memory, reward, attention, body sensations, decision making and emotional displays, all of which can contribute to feeling sad. Sadness triggers also vary—for example, the memory of a personal loss; a friend stressing over a work conflict; seeing a desolate film.
In the brain, happiness is as widely distributed as sadness. In his book "This Is Your Brain on Music," Dr. Daniel Levitin (page 58) notes that music simultaneously enlists many parts of the brain. We listen and respond to sounds and rhythms (auditory, sensory and motor cortex, cerebellum). We interpret (sensory cortex) and reason (prefrontal cortex). Music pulls on memories for experience and emotion (amygdala and hippocampus). If the music is working for you, it is probably triggering the reward system (nucleus accumbens). And if you're playing it, as Dr. Levitin does, you also get to throw satisfaction into the mix. This may or may not be a description of happiness, but it certainly coincides with the notion of flow, described by the author Dr. Mihály Csíkszentmihályi: concentrated attention and the absence of self-consciousness. A neuroscientist might say that a life that fully engages your brain in these ways is a life worth living.
Faith, Love and Understanding
The challenge to cognitive neuroscientists becomes greater as we go up the ladder to more-complicated emotional states. And the stakes become higher, too, because research into such highly valued and personal mental processes can be easily misunderstood.
Empathy is more than being nice. It is the ability to feel what another person feels, and in its most refined form it is the capacity to deeply understand another person's point of view. The brain's empathic powers actually begin with fear detection. Most of us are extraordinarily skilled face readers. We readily act on the emotions communicated to us through facial expression. And the grammar of facial expression, in some instances, is plain. We are masters at telling when a smile is insincere by the absence of wrinkles (called Duchenne lines) around the smiler's eyes. In a spontaneous smile, the corners of the mouth curl up and muscles around the eyes contract. Duchenne lines are almost impossible to fake.
In the Marx Brothers movie "Duck Soup," Groucho encounters his brother Chico in a doorway, dressed like him in a nightshirt and cap and a fake mustache. They perform a famous version of the mirror routine, Chico copying Groucho's actions. The humor may derive, at least in part, from humans' highly developed skill as copycats. When you observe someone eating ice cream or stubbing a toe, the brain regions that are activated in the eater and the stubber are also activated in you.
But empathy depends on more than an ability to mirror actions or sensations. It also requires what some cognitive neuroscientists call mentalizing, or a "theory of mind." Simon Baron-Cohen, a leading researcher in the study of autism, has identified the inability to generate a theory of mind as a central deficit in that illness. He has coined the term "mindblindness" to designate that problem. The corollary, "mindsightedness," requires healthy function in several areas of the brain. The processing and remembering of subtle language cues take place toward the ends of the temporal lobes. At the junction of the temporal and parietal lobes, the brain handles memory for events, moral judgment and biological motion (what we might call body language). And the prefrontal cortex handles many complex reasoning functions involved in feelings of empathy.
Not surprisingly, love also engages a whole lot of brain. Areas that are deeply involved include the insula, anterior cingulate, hippocampus and nucleus accumbens— in other words, parts of the brain that involve body and emotional perception, memory and reward. There is also an increase in neurotransmitter activity along circuits governing attachment and bonding, as well as reward (there's that word again). And there's scientific evidence that love really is blind; romantic love turns down or shuts off activity in the reasoning part of the brain and the amygdala. In the context of passion, the brain's judgment and fear centers are on leave. Love also shuts down the centers necessary to mentalize or sustain a theory of mind. Lovers stop differentiating you from me.
Faith is also being studied. Earlier this year the Annals of Neurology published an article by Sam Harris and colleagues exploring what happens in the brain when people are in the act of either believing or disbelieving. In an accompanying editorial, Oliver Sachs and Joy Hirsch underscored the significance of what the researchers found. Belief and disbelief activated different regions of the brain. But in the brain, all belief reactions looked the same, whether the stimulus was relatively neutral: an equation like (2+6)+8=16, or emotionally charged: "A Personal God exists, just as the Bible describes."
By putting a big religious idea next to a small math equation, some readers might think the researchers intend to glibly dismiss it. But a discovery about brain function does not imply a value judgment. And understanding the reality of the natural world—how the brain works—shouldn't muddle the big questions about human experience. It should help us answer them.