Watching the Brain Bring Emotions to Life
NEW ORLEANS — In pursuit of happiness, fear and the other feelings played on the mood organ of the mind, scientists for the first time are systematically exploring the anatomy of emotion.
Mapping the brain’s emotional landscape, researchers are learning how love alters the brain’s neural activity. They have detected the inner turmoil that strong words can stir.
They can see how the biochemistry of feelings clouds the brain’s ability to think clearly or create accurate memories. They are discovering how the brain must change its emotional ways to master the dark disturbances of depression.
By examining the complex neural circuits that underpin emotional states, researchers are tackling a subject long considered too subjective and ill-defined for fundamental scientific study.
Once relegated to the fringe, the study of emotion in recent years has taken on new respectability with technical advances that make it possible to reliably monitor such subtle mental states. Positron emission tomography (PET) and functional magnetic resonance imaging have become tools of choice for the painless dissection of human emotion.
“Emotion research has been a stepchild,†said Steven Hyman, director of the National Institute of Mental Health. “Until recently, the study of emotion was seen as suspect compared to the study of cognition.
“Now we are seeing that, like thinking, emotions rely on specific neural circuits,†Hyman said. “We are just at the beginnings of understanding how these circuits interact, of understanding how thinking and emotions interact.â€
Researchers are learning in detail how the brain treats human emotion as a type of information. This information is processed through neural circuits shaped by evolution to bolster individual survival or to regulate the body’s biochemical well-being.
Emotion, scientists are discovering, is not centered in any one part of the brain, but reaches into almost every furrow of the dynamic and fickle organ of thought.
“Emotion is not regulated in one place; it is a network of areas,†said neuropsychiatrist Dr. Helen Mayberg at the University of Toronto, who uses a variety of imaging techniques to study the neurobiology of depression and other mood disorders. Emotion is the body’s way of tying together a range of physical, mental and biochemical responses, she said.
“You need to have a system that will link up your thinking, feeling, your gut reaction, your subconscious reactions, to coordinate your thinking with the automatic parts of your brain.â€
New findings about the nature of emotion presented at a recent meeting of the Society for Neuroscience in New Orleans, combined with studies published this fall in several peer-reviewed journals, have illuminated the scope of neural circuits responsible for the private life of the brain:
* Each emotion generates a unique pattern in the brain. Antonio Damasio at the University of Iowa has identified distinctive, measurable patterns in PET scans of nerve cell activity that appear during each emotional state, including areas not normally associated with feelings.â€The pattern can be triggered automatically,†Damasio said. “It occurs by the design of our biology.â€
* Moods can powerfully bias what people think, remember and perceive. Extreme emotions trigger heightened neural activity that appears to interfere with the brain’s ability to process information, Dr. Marcus Raichle determined. A pioneer in brain imaging at Washington University in St. Louis, Raichle said, “The finding helps explain, on a scientific level, why emotion sometimes clouds thinking.â€
* Love changes everything, including some neural responses in the brain. Andreas Bartels and Semir Zeki at University College London have detected a distinctive pattern of brain activity among those deeply in love, suggesting that a specialized brain system is behind the euphoric high of romance. They scanned the brains of 17 volunteers who said they were deeply in love, as they looked at a picture of their heart’s desire, then compared their neural activity to that of people who were merely friendly.
* Subtle damage to the mental machinery of fear may be responsible for many common psychiatric disorders, even a reckless disregard for the well-being of others. Animal experiments by Joseph LeDoux at New York University’s Center for Neural Science and others are revealing, molecule by molecule, the pathways that fear travels into memory and thought.
* The dark curtain of depression lifts only when the brain can recalibrate itself. Mayberg and her colleagues sought to understand why antidepressant drugs such as Prozac take weeks to work for some people but never have any effect on others.
The researchers found widespread patterns of change in the brains of those who were helped by Prozac, compared with those who were not, in a transformation that took weeks to complete. “There is a whole set of changes that need to happen for the brain to set a path for recovery,†Mayberg said.
In many ways, human feelings are all on the surface for any eye to behold.
They are displayed through an eloquent vocabulary of facial expressions that British naturalist Charles Darwin considered a universal human language for the communication of emotion, crafted by evolution long before the spoken word developed.
But not until scientists could watch the living brain with noninvasive imaging technologies did they get their first real inkling of what transpires when an emotion wells up from within.
“In the study of emotion,†said Mayberg, “it is really exciting that we have these tools. Otherwise all you can do is build theories. The tools now make us honest. Talk is cheap, and we have had just talk about emotion for thousands of years.â€
So new is the use of brain scanning in the study of emotion, however, that some scientists worry that researchers may be reading too much into the complicated patterns of neural activity they now can detect in the brain and making sweeping claims about emotion that their experimental data cannot support.
To be sure, it is a struggle to decipher the split-second responses of brain metabolism and neural blood flow and find the appropriate emotional state, because it is all but impossible to define human feelings with scientific precision, several experts said.
Indeed, poets and lyricists have struggled for centuries to find the proper words to describe gradations of love, grief and the other shadings on the emotional palette. By themselves, brain waves can be no less ambiguous.
“I see a lot of loose, fuzzy thinking,†said LeDoux, author of “The Emotional Brain.†“People want to study emotion but they don’t know what they mean by it.
“They don’t have a theory, just a popular topic.â€
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Hotz can be reached at [email protected].
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The Palette of Emotion
The human brain generates distinct neural blueprints of sadness, happiness, anger and fear, researchers have shown. Scientists at the University of Iowa captured these images of the neural activity that arises during emotional states using positron emission tomography (PET) to monitor 41 volunteers while they recalled emotionally powerful moments. Brain activity is measured on a spectrum scale, with the highest levels in deep red and the lowest in purple. These images of cross sections taken at different depths of the brain show that emotions involve neural circuits throughout the brain, not any one area.
Source: Nature Neuroscience, University of Iowa
