November 16, 1998
Volume 51, No. 12
Davis looks at fear, which underlies many mental illnesses
Fear has halted live performances by people like Barbra Streisand. It has even forced football commentator John Madden to avoid planes and instead take long, cross-country bus rides as he goes from game to game.
Woodruff Professor of Psychiatry Michael Davis studies the parts of the brain involved in fear and anxiety. Anxiety is the root of many types of psychiatric diseases, and Davis and other scientists hope that understanding the disorder's underlying biology will eventually lead to treatments.
Newly arrived at Emory after a 33-year career at Yale, Davis said his decision to become part of Emory was determined by "the people and the excitement about Emory wanting to become a more established medical school." And the Davis lab, which consists of two graduate students and two postdoctorates, also has a great deal to offer the Emory community.
Describing the difference between normal anxiety and unhealthy anxiety as a matter of degree and not kind, Davis said he sometimes suffers a mild form of the most common fear: public speaking. "We're all anxious when we take a test," he said, "but we can all get through it." But in the case of generalized anxiety, panic disorder and post-traumatic stress, people see their lives held hostage by apprehension.
However, anxiety is more easily studied than disorders such as schizophrenia because it can be examined through animal models. "When you're walking down an alley and you hear a loud noise, you feel yourself jump," Davis said, describing the startle reflex, which can be measured in both humans and rats.
To do so researchers tape tiny electrodes under the eyes of human subjects and measure the strength of a fear-induced blink. Participants are told they will receive a small shock to the hand when a blue light illuminates but no shock when a yellow light illuminates. Numerous encounters with both lights ensue, causing reinforcement. Then researchers measure the startle reflex by following the blue light with a loud noise. Expecting a shock, the tensed subjects blink in fear, and the startle reflex is measured. The process is similar for rats, although researchers measure the rats' jumps instead of eye blinks.
These studies have shown that an area of the brain called the amygdyla becomes very active during the fear response, and rats without amygdylas show no fear reaction. They've also proven that behavioral strategies can dampen this reflex, and drugs that target the amygdyla can lessen or heighten the fear response. By understanding how fear occurs in the brain, scientists will one day know how to better control its ill effects.
One approach is to find how the brain naturally represses the amygdyla. "Just as there are parts for fear, there are parts to suppress," Davis said. He is currently searching for these areas to learn their biology, hoping one day to help inhibit unnatural anxiety.
Moreover, in the way scientific query often leads to more questions, Davis' focus on anxiety has lead him to examine the neurobiology of learning and memory. "There's lots of data and evidence suggesting that the site of plasticity, the site of learning, may be in the amygdyla," said Davis. "If you burn yourself on a radiator when you're 3 years old, you'll never touch that radiator again. So that one episode lays down a memory that lasts a lifetime. There must be some very profound chemical and morphological changes in the brain."