Sad Brain, Happy Brain

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 Itself
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.