Brain's Design Emerges As a Key to Emotions

By DANIEL GOLEMAN

New York Times

Published: August 15, 1989

LEAD: THE power of emotions to override even the most rational decisions may be explained by a new discovery about the brain, researchers say. The data suggest that the brain is arranged so key aspects of emotional life, like primitive fears, can operate largely independent of thought.

THE power of emotions to override even the most rational decisions may be explained by a new discovery about the brain, researchers say. The data suggest that the brain is arranged so key aspects of emotional life, like primitive fears, can operate largely independent of thought.

This arrangement may explain why certain emotional reactions, like phobias, are so tenacious despite their obvious irrationality. It may also explain other baffling facts of emotional life, such as why troubling experiences from life's earliest years can have such powerful effects decades later.

''This may explain why we have so little reflective insight into our emotional life,'' said Dr. Joseph LeDoux, a psychologist at the Center for Neural Science at New York University. Dr. LeDoux did many of the key studies that underlie the new view of emotion and the brain while at the Laboratory of Neurobiology at Cornell Medical Center in Manhattan.

''Dr. LeDoux has made a major discovery about the emotional side of learning, one with major implications for learned pathologies like neuroses and phobias,'' said Dr. Norman Weinberger, a neuroscientist at the Center for the Neurobiology of Learning and Memory at the University of California at Irvine.

Tne new work is, so far, known largely among specialists in cognitive neurobiology, a field that specializes in tracing connections between the brain and psychological life. While further studies will be needed to verify the findings of Dr. LeDoux and their significance, other researchers have already begun to use his results in their own work. Dr. Weinberger, for instance, is applying the findings in his studies of memory problems in Alzheimer's disease.

Dr. LeDoux's research, which was done entirely in rats, included such standard techniques as cutting specific nerve pathways in the brain to see how it changed the rats' behavior.

''The architecture of the mammalian brain is basically the same in all species, but you can't do these kinds of studies in a human brain,'' Dr. LeDoux explained.

The new evidence suggests that certain emotional reactions occur before the brain has even had time to fully register what it is that is causing the reaction; the emotion occurs before thought. That view is a direct challenge to the prevailing wisdom in psychology, that emotional reactions follow from thoughts about a situation.

The data also call into question a longstanding view about just which brain structures link together to form the ''limbic system,'' which regulates emotional life. The hippocampus, which has long been considered part of the limbic system, may be more involved with registering cognitive information than emotions, according to findings of other researchers reviewed by Dr. LeDoux in an article to appear in the journal Cognition and Emotion this year.

His own data put another part of the limbic system, the amygdala, at the center of the primitive emotional reactions that seem to operate independent of, and prior to, thought.

Scientists had assumed that the amygdala, part of the brain that registers emotion, depended on signals from the neocortex, the thinking part of the brain, to form an emotional reaction. The work of Dr. LeDoux suggests that in many cases the amygdala triggers an emotional reaction before the thinking brain has fully processed nerve singals. Deep-Rooted Emotions

''To simplify greatly, the hippocampus seems to be the focal point for cognition and the amygdala for emotion,'' Dr. LeDoux said. ''The hippocampus, for instance, is involved in recognizing a face and its significance, such as that it's your cousin. The amygdala adds that you really don't like him. It offers emotional reactions from memory, independent of your thoughts at the moment about something.

Emotional reactions and emotional memories can be formed without any conscious, cognitive participation at all, because anatomically the emotional system can act independently.'' Dr. LeDoux said.

While other researchers had recorded activity in the thalamus or the amygdala during the moments when fear is learned, it was Dr. LeDoux who discovered the direct connection that links them during the process.

''Dr. LeDoux's research is the first to work out neural pathways for emotional response that don't go through the cortex,'' said Dr. Michael Gazzaniga, a psychiatry professor at Dartmouth Medical School. ''It may explain why so much of emotional life is hard to understand with the rational mind.'' 'Missing Piece of Puzzle'

Dr. Weinberger said, ''It's the missing piece of the puzzle, showing that fear can be learned without the cortex being involved. It brings to amygdala to the forefront in studying emotions.''

The prevailing view among neuroscientists is that the eyes, ears and other sensory organs transmit signals to the thalamus, and from there to sensory processing areas of the neocortex, where the signals are put together into objects as people perceive them.

The signals are sorted for meanings so that the brain recognizes what an object is and what its presence means. From the neocortex, the signals are sent to the amygdala. Thus emotional reactions usually follow from cognitive understanding.

But Dr. LeDoux has discovered nerve pathways that lead directly from the thalamus to the amygdala, in addition to those going through the cortex. That means that the amygdala can also receive direct inputs from the senses before they are fully registered by the rest of the brain.

Thus emotions can be triggered before the brain has had time to fully register just what it is that is being responded to. This is most pronounced in an emergency, when an instant response is required.

''The amygdala is just one synapse away from the thalamus, while the hippocampus is several additional synapses away,'' Dr. LeDoux said. That means a difference of as much as 40 milliseconds, about a twenty-fifth of a second, in the time it takes a sensory signal to reach the amygdala as compared with the hippocampus, Dr. LeDoux said. Aid in Responding Quickly

That time gap allows the amygdala to respond to an alarming situation before the hippocampus does. For instance, if in the corner of your eye you see what looks like a snake, it is the amygdala that sends the signal of alarm that makes you jump. You react even before the hippocampus has had time to figure out if it was actually a snake or a piece of rope.

This arrangement has had great survival value in evolution, Dr. LeDoux believes. He observes that in more primitive species, like birds, fish and reptiles, the connections between the thalamus and the amygdala play a major role in mental life.

''This primitive, minor brain system in mammals is the main system in nonmammals,'' Dr. LeDoux said. ''It offers a very rapid way to turn on emotions. Those extra milliseconds may be lifesaving, which is a powerful advantage in evolution. But it's a quick and dirty process; the cells are fast, but not very precise.''

The amygdala triggers what Dr. LeDoux calls ''pre-cognitive emotion,'' feelings independent of thought.

''Pre-cognitive emotion is based on neural bits and pieces of sensory information, which have not yet been sorted out and integrated into a recognizable object,'' he said. ''It's a very raw form of sensory information like recognizing the notes without noticing the melody.'' Patterns From Infancy

Dr. LeDoux believes these pre-cognitive emotions may be at work in many areas of human mental life. For instance, they may explain the nature of the emotional life of infants, and the lifelong persistence of emotional patterns formed in infancy.

''A tremendous amount of learning takes place during the first two years of life, yet we have little if any conscious recall from those years,'' Dr. LeDoux said. The reason it is so hard to remember experiences from those years, he believes, is because the hippocampus is not fully mature at birth, while the amygdala is more fully formed during the first years of life.

That may also explain why the emotional experiences of life's earliest years, which psychoanalysts have long pointed to as key to later emotional life, are both so potent and so difficult to understand rationally.

As psychotherapists have long known, emotional memories - like deep fears or resentments - are particularly persistent and hard to counter. Dr. LeDoux is soon to publish research showing that these robust emotional habits are formed and stored in the amygdala.

In an article to be published this month in The Journal of Cognitive Neuroscience, Dr. LeDoux reports a study with laboratory rats that were taught to fear a flashing light by having it paired with a shock. Ordinarily, once the fear is learned, it can be gradually extinguished by regular displays of the lights without the shock; this process typically takes several weeks.

When some of the rats had their visual cortexes removed, they still learned to fear the lights - evidence that it is the connection to the amygdala that is crucial in forming such fears. When those same rats were shown the lights without the shock for several weeks, they retained fearfulness, unlike rats whose brains had the cortex intact. Formation of Phobias

This may explain how phobias are formed in humans, and why they can be so tenacious, Dr. LeDoux said.

''In people who have gotten over a phobia, a single scary experience can sometimes suddenly bring it back in full force,'' he said. ''That means the phobia had not been lost to emotional memory, even though the behavior had been extinguished.''

The implications of Dr. LeDoux's work for psychotherapy are in offering a neuroanatomical explanation for phenomenon long observed.

''Once your emotional system learns something, it seems you never let it go,'' Dr. LYDoux said. ''What therapy does is teach you to control it. It teaches your cortex how to inhibit your amygdala. The propensity to act is suppressed, while your basic emotions about it may remain in a subdued form.''

The psychoanalytic view that the unconscious mind has profound influence in mental life also finds support in Dr. LeDoux's work. ''While some emotional memories may reach consciousness, there are many emotional memories that lead to actions, but which we do not consciously remember,'' Dr. LeDoux said.

He cited a study showing that people formed preferences for geometric shapes flashed so quickly that they were not aware of having seen them. His own work suggests that the amygdala may be involved in such preferences.