What if the real source of pain isn’t your body, but your brain’s reaction to it?

That’s the question researchers at the Salk Institute are exploring through a groundbreaking discovery: a previously hidden neural pathway that gives pain its emotional weight.

Published in the Proceedings of the National Academy of Sciences (read the study), the study reveals a distinct group of CGRP-expressing neurons in the thalamus that connect physical pain to emotional suffering. This may help explain why some people experience pain more intensely, and suffer from it more deeply, than others.

A hidden amplifier in the brain

For decades, scientists believed that the brain processes pain through two separate routes: one for the raw sensation and another for its emotional toll. The sensory side followed the spinothalamic tract, a nerve highway that carries pain signals from the spinal cord to the thalamus and then to the brain’s sensory regions. The emotional dimension was thought to travel along a separate path through the brainstem and into the limbic system.

But the Salk team, led by neuroscientist Sung Han, found evidence that reshapes that view. Using advanced imaging and genetic tools in mice, they discovered that some spinothalamic neurons project into a lesser-known part of the thalamus called the SPFp. These neurons express CGRP, a neuropeptide already linked to migraine pain and heightened threat sensitivity.

From the SPFp, these CGRP-tagged neurons send signals directly to the amygdala, the brain’s emotional processing hub. When researchers silenced these neurons, mice still reacted to painful stimuli but didn’t appear to mind. They showed no signs of lasting fear or avoidance. When the same neurons were artificially activated, the mice avoided the associated location—even when no pain had been delivered.

As first author Sukjae Kang explained, “Pain processing is not just about nerves detecting pain; it’s about the brain deciding how much that pain matters.”

Why suffering lingers

This newly uncovered pathway may help explain why conditions like fibromyalgia and migraine can feel unbearable even in the absence of visible injury. People living with these disorders often describe long-lasting pain, hypersensitivity to stimuli, and emotional exhaustion.

The Salk researchers found that CGRP neurons in the SPFp express many genes associated with pain disorders, suggesting that this pathway may be hyperactive in people with chronic pain.

The discovery could also help clarify the neurological roots of PTSD. Symptoms like hypervigilance, fear conditioning, and persistent avoidance may stem in part from this same CGRP circuit, which appears to act as an internal alarm system for threats and discomfort.

Drugs that block CGRP already exist for treating migraines. Medications such as Aimovig and Nurtec were developed to stop CGRP from triggering inflammation and vascular pain responses. But their ability to reduce the emotional burden of pain might be a key reason they work so well. Some patients even report feeling more emotionally balanced alongside their physical relief.

Turning down the volume

Pain is deeply personal. Most people begin to feel it at about the same threshold, but how much it distresses them can vary widely. This study offers a biological explanation for that difference.

The Salk team believes future treatments could target the brain’s emotional amplifier without silencing the sensory alarm system. That shift could mark a new era in pain relief, focused not just on numbing sensation, but on easing the mind’s suffering.

“Our discovery of the CGRP affective pain pathway gives us a molecular and circuit-level explanation for the difference between detecting physical pain and suffering from it,” said Han.

If the findings extend to humans, this CGRP pathway could become one of neuroscience’s most valuable therapeutic targets. The goal isn’t to erase pain completely, but to prevent it from becoming overwhelming.