When a stranger put a knife to S.M.’s throat and threatened to kill her, she didn’t even flinch.

Rather, S.M. — as she is known at the UI Hospitals and Clinics — looked at the man and simply told him he would have to go through her angels before he could harm her.

S.M. is missing her amygdala, an almond-shaped structure considered the main hub of the brain’s fear network. And UIHC researchers are eager to learn more about the rare condition.

Justin Feinstein, a graduate student seeking his Ph.D. in clinical neuropsychology, is the lead researcher working with S.M. He discovered her when she was a patient at the UIHC. After learning about her condition, he asked S.M. if she would volunteer as a research subject, and she agreed.

In S.M.’s case, Feinsten was interested in the implications of living in a virtually fear-free world.

While studying her, the middle-age woman told Feinstein about some of the dangerous situations she has unwittingly gotten herself into.

“She gets in a lot of trouble because she can’t sense when a dangerous situation is arising,” he said.

Through numerous probing discussions with S.M., Feinstein said he hopes his team will be able to help doctors better understand patients with similar conditions.

Feinstein usually finds subjects through the world-renowned Iowa Patient Registry, a database of more than 3,000 patients with a variety of rare brain disorders.

David Rudrauf, director of the laboratory of brain imaging and cognitive neuroscience, said department officials strive to keep the registry large and diverse to accommodate the school, as well as patients such as S.M.

“We want to have patients who cover every part of the brain,” he said. “We try to get as many as we can to cover all the areas.”

Patients from across the nation clamor to be added to the list, Feinstein said.

Feinstein targets patients in the registry who are missing areas of the brain important for emotion, like S.M. Another such patient is “Roger” — a man whose limbic system, a collection of brain regions thought to be critical for feeling emotion, was destroyed by a virus nearly 30 years ago.

Rudrauf joined Feinstein in conducting research on Roger, and said the patient’s disorder was the first one like it they had seen.

“It’s rare that a disease affects the brain that much,” he said.

The research team worked to discover if the missing parts of Roger’s brain were truly critical for a person to feel emotion.

Feinstein showed Roger emotion-provoking movies. Surprisingly, Roger appeared to display all of the appropriate emotions — ranging from intense laughter while he watched comedy sketches to sighs of compassion while watching children suffering from starvation.

The testing on Roger has led to a series of projects aimed at understanding how he is still capable of feeling emotion even though his limbic system was destroyed.

Despite the ground-breaking research like Feinstein’s conducted within the department, the 28-year-old said he is worried about the UI’s ability to keep their top clinicians and recruit more, saying the UI has lost several senior researchers since he arrived in 2005.

He added the type of research conducted within the neurology department is crucial for developing an understanding of brain-behavior relationships.

“It’s important for the UI to continue to fund this sort of work,” he said. “This allows neuroscientists to say something definitively about what these areas of the brain are doing.”