How the brain’s ‘central alarm system’ gathers threats and turns them into fear



Fear is a natural emotion triggered by a perceived threat. However, it can also be a factor in fear-related mental health conditions. Scientists believe the biological processing of fear occurs in a part of the brain called the amygdala — though other brain regions like the thalamus and brainstem may also play a role.

How this process occurs is not fully understood, but new research shows how specific molecules in separate parts of the brain gather and transmit threat cues to the amygdala, which transforms them into fear. Researchers suggest their findings may lead to new therapies for fear-related mental health conditions, migraine, and hypersensitivity disorders often experienced by autistic people. Fear is a natural emotion in humans and animals that can help detect and respond to real or perceived danger.

When a person perceives a possible threat, biochemical reactions occur to prepare the body and mind to respond — known as the fight, flight, or freeze response.

A 2016 research review discusses that this fear response is processed in a brain region called the amygdala. When faced with a possible threat, the brain receives information from the sensory systemTrusted Source through sight, sound, smell, and touch. Then, this information activates parts of the amygdala to initiate the behavioral reactions required to deal with the threat.

Yet the brain pathways responsible for gathering threatening information from the body’s sensory system and initiating the fear response are not fully understood, but new research offers some clues. A recent studyTrusted Source from the Salk Institute for Biological Studies in La Jolla, California, may have uncovered one of those pathways. In the study, scientists discovered populations of a molecule called calcitonin gene-related peptide (CGRP) that allows neurons to transmit threatening cues between separate areas of the brain, then relay that information to the amygdala.

To conduct the research, scientists used single-cell calcium imaging to record the CGRP neuron activity of mice exposed to threat cues that stimulated multiple senses. Using differently colored fluorescent proteins, they were then able to track the pathways of signals leaving the thalamusTrusted Source — a brain region responsible for relaying sensory information — and brainstem.

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