PASADENA, Calif.The eerie music in the movie theater swells; the roller coaster crests and begins its descent; something goes bump in the night. Suddenly, you're scared: your heart thumps, your stomach clenches, your throat tightens, your muscles freeze you in place. But fear doesn't come from your heart, your stomach, your throat, or your muscles. Fear begins in your brain, and it is therespecifically in an almond-shaped structure called the amygdalathat it is controlled, processed, and let out of the gate to kick off the rest of the fear response.
In this week's issue of the journal Nature, a research team led by scientists at the California Institute of Technology (Caltech) has taken an important step toward understanding just how this kickoff occurs by beginning to dissect the neural circuitry of fear. In their paper, these scientistsled by David J. Anderson, the Benzer Professor of Biology at Caltech and a Howard Hughes Medical Institute investigatordescribe a microcircuit in the amygdala that controls, or "gates," the outflow of fear from that region of the brain.
The microcircuit in question, Anderson explains, contains two subtypes of neurons that are antagonistichave opposing functionsand that control the level of fear output from the amygdala by acting like a seesaw.
"Imagine that one end of a seesaw is weighted and normally sits on a garden hose, preventing waterin this analogy, the fear impulsefrom flowing through it," says Anderson. "When a signal that triggers a fear response arrives, it presses down on the opposite end of the seesaw, lifting the first end off the hose and allowing fear, like water, to flow." Once the flow of fear has begun, that impulse can be transmitted to other regions of the brain that control fearful behavior, such as freezing in place.
"Now that we know about this 'seesaw' mechanism," he adds, "it may someday provide a new target for developing more specific drugs for treating fea
|Contact: Jon Weiner|
California Institute of Technology