What MRI and 100 years of horror movies can teach us about our brains

They’re scary, sometimes cheesy, but everyone has strong reactions to horror movies. And researchers from Finland recently turned to imaging in an effort to better understand why.

A team from the University of Turku’s PET Center measured the brain activity of volunteers who watched some of the past century’s most frightening horror movies while inside an MRI scanner. They were able to map neural activity in response to these films, noting psychological horror films based on real events were scariest, especially when things were unknown.

“This latter distinction reflects two types of fear that people experience,” Lauri Nummenmaa, professor at Turku’s imaging center, said in a statement. “The creeping foreboding dread that occurs when one feels that something isn’t quite right, and the instinctive response we have to the sudden appearance of a monster that make us jump out of our skin.”

To begin their experiment, the Finnish researchers established the 100 best and scariest horror movies based on their IMDb ratings, and evaluations from 216 “filmaholics.”  Thirty-seven participants then watched two horror movies (“The Conjuring 2” and “Insidious”) in an MRI scanner while Nummenmaa et al. analyzed their hemodynamic brain activity.

During the movie, as anxiety began to slowly increase, areas of the brain involved in visual and auditory perception started to activate, a response to rising environmental threats, the researchers noted. And after a sudden shock, such as a “jump scare,” activity was more apparent in regions involved in processing emotion, evaluating threats and decision-making. This was the brain equipping itself for a quick response.

“These data suggest that acute and sustained fear are supported by distinct neural pathways, with sustained fear amplifying mainly sensory responses, and acute fear increasing activity in brainstem, thalamus, amygdala and cingulate cortices,” the investigators wrote this month in NeuroImage.

Despite these activation differences, brain regions were in constant communication with sensory areas of the organ, indicating regions don’t work in isolation, but shift depending on the impending threat level and proximity, the authors found.

“Our brains are continuously anticipating and preparing us for action in response to threat, and horror movies exploit this expertly to enhance our excitement,” first author Matthew Hudson, with Turku’s PET Center, concluded.