Researchers this week announced they had discovered an “on-off” switch in the brain that controls the emotional response to fear, and said it could someday lead to new treatments for anxiety disorders.

The research team, from Columbia University Medical Center, used a simple attention test and a type of real-time brain scan called functional magnetic resonance imaging, which can catch the brain in action.

The test showed that an area in the rostral cingulated, or rACC, region of the brain was involved in turning on or off the fear response in the amygdala – the almond-shaped center in the brain where emotional responses to fear are processed.

Dr. Joy Hirsch, the head researcher in the study, said, “People are exposed to an ever-increasing amount of stimuli in our everyday lives, and so we realized that the brain must employ a processing mechanism to prioritize and refine responses – we don’t run away from every loud sound or unexpected sight.”

They used a test called the Stroop test to try to activate whatever region must be involved.

The Stroop test measures mental flexibility by forcing people to choose between a word’s meaning and its color. For example, someone may be asked to read a list of words like “yellow,” “red,” or “green” in which the word “red” might be written in blue ink, “yellow” in pink ink and so on. People normally respond more quickly if the color and word match.

The team adapted the test, using photos of fearful and happy faces, with “FEAR” or “HAPPY” written on the images. They administered the test to 19 healthy volunteers and ran the brain scan at the same time. The rostral cingulated seemed to light up just before the amygdale was activated, the researchers found.

For example, the amygdala activated at first if FEAR was written on the happy image, and then the rostral cingulated would activate, apparently as the image of the smiling face registered, after which the amygdala would calm down, they said.

But the amygdala stayed activated for longer, and the rostral cingulated remained unlit for a longer period of time, if a fearful face also carried the “FEAR” label. Hirsch said it is critical to have a circuit to control the fear response.

Some patients with anxiety disorders and depression may eventually find benefits from the study’s findings, according to Dr. Eric Kandel, a Howard Hughes Medical Institute senior investigator and professor who also worked on the paper.

He continued, “For example, if someone with anxiety has a disturbed functioning of part of the amygdala or a disturbed functioning of rostral cingulate control mechanism, and treatment could be based on the individual’s specific problem.

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