Investigators have found that fear may have its roots in several
brain regions — and not necessarily in the amygdala, a brain
structure known to register fear from external dangers.
Researchers at the University of Iowa conducted tests on three
women with significant damage to the amygdala. When doctors at
the University of Iowa prepared a patient to inhale a panic-
inducing dose of carbon dioxide, she was fearless. But within
seconds of breathing in the mixture, she cried for help,
overwhelmed by the sensation that she was suffocating. The
patient, a woman in her 40s known as SM, has an extremely rare
condition called Urbach-Wiethe disease that has caused extensive
damage to the amygdala, an almond-shaped area in the brain. She
has not felt terror since getting the disease when she was an
adolescent. From this research, scientists hypothesize that the
amygdala is not the only gatekeeper of fear in the human mind.
Other regions — such as the brainstem, diencephalon, or insular
cortex — could sense the body’s m