Spiders, heights, or public speaking: Each fear has a unique place in the brain

Fear strikes in many forms – standing on the edge of a towering skyscraper, glimpsing a tarantula, or feeling your heart race as you prepare to deliver a speech.

The scientific community long believed these scenarios stimulated brains similarly.

“There’s this story that we’ve had in the literature that the brain regions that predict fear are things like the amygdala, or the orbital frontal cortex area, or the brainstem,” said Ajay Satpute, an associate professor of psychology at Northeastern University.

“Those are thought to be part of a so-called ‘fear circuit’ that’s been a very dominant model in neuroscience for decades.”

Challenging the fear circuit model

In early October 2024, Satpute and his team released a study challenging this long-held belief.

The researchers used MRI scans to examine the brain’s response to three distinct fear-inducing scenarios: fear of heights, spiders, and public speaking.

Contrary to prior assumptions, the study revealed each type of fear activated different brain regions, debunking the idea of a universal “fear circuit.”

“Much of the debate on the nature of emotion concerns the uniformity or heterogeneity of representation for particular emotion categories,” noted the researchers.

The team discovered that “the overwhelming majority of brain regions that predict fear only do so for certain situations.”

Research suggests responses to fear are more specific than previously thought. These findings carry important implications for understanding anxiety across species, and how to develop neural signatures for personalized treatments.

Machine learning and fear in the brain

The research tested long-standing assumptions about how fear works, particularly as neuroscience increasingly relies on AI and machine learning to predict emotions.

“Most of those approaches assume that there is a single pattern that underlies the brain-behavior relationship: there’s a single pattern that predicts disgust. There’s a single pattern that predicts anger,” said Satpute.

“Well, if that’s true, then such a pattern should be apparent for different varieties of fear.”

However, when it comes to fear, the study showed a more complex picture.

Focus of the research

In the experiment, the researchers asked 21 participants to identify their fears and used magnetic resonance imaging (MRI) scans to monitor brain activity as they watched videos depicting anxiety-inducing scenarios.

“We tried to find really scary videos of spiders,” Satpute said. “Because I don’t want a neural predictive model that ‘says you’re looking at a spider.’ I want a neural predictive model that says ‘you’re experiencing fear.'”

Revealing fear’s hidden complexities

Following each video, participants rated their levels of fear, valence (how pleasant or unpleasant the experience was), and arousal on a questionnaire.

The study revealed two surprising insights: responses were observed in a wider array of brain regions and not all brain regions were involved across all scenarios.

“The amygdala, for instance, seemed to carry information that predicted fear during the heights context, but not some of the other contexts,” Satpute said. “We’re not seeing these so-called ‘classic threat areas’ involved in being predictive of fear across situations.”

Body’s response to emotional triggers

The research is part of a broader body of work from Satpute’s lab, which focuses on understanding how fear manifests in the body.

In a previous 2021 study, the team explored physiological responses to fear such as sweat and heart rate when facing different triggers like heights or confrontations with law enforcement.

The study also revealed that different triggers caused varied bodily reactions, supporting the idea that fear isn’t one-size-fits-all.

Implications for future treatments

Satpute hopes to replicate these findings with a larger and more diverse participant pool and factoring in demographics like age and gender.

While the current study has a small sample size, the results could reshape how health professionals approach treating fear and anxiety disorders.

“When we look at the brain and the neural correlates of fear, part of the reason we want to understand is so we can intervene on it,” noted Satpute. “Our findings suggest the interventions might also need to be tailored to the person and situation.”

Revolutionizing fear-based therapies

This shift in understanding could revolutionize behavior-based therapies for conditions like phobias and PTSD. It might even impact drug-based treatments.

“Drug-based therapies that target a particular circuit do work, but only for about fiftyish percent of people,” Satpute said. “It’s not really clear why.”

“Our research offers at least some explanation – the brain regions that are going to matter for any emotional experience are going to vary by the person and situation. If you focus only on what’s common, you ignore so much.”

This understanding of fear moves beyond the idea of a “fear circuit” and opens doors for personalized treatments.

Whether it’s the fear of falling, facing a spider, or standing in front of an audience, the research shows fear is more complex than once believed.

The study is published in The Journal of Neuroscience.

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