For people living with chronic back pain, even a simple movement can trigger a sudden surge of pain. Now, scientists have discovered that these painful episodes activate a surprising part of the brain, one closely connected to our sense of identity and how we think about ourselves.
Researchers at UC San Diego School of Medicine found that movement-triggered pain in people with chronic low back pain (cLBP) activates a brain network that normally becomes less active during ordinary pain. The discovery suggests that persistent back pain may become deeply intertwined with a person's sense of self, potentially helping explain why conventional pain treatments often provide limited relief.
According to the World Health Organization, low back pain is the leading cause of disability worldwide. When pain persists for more than 12 weeks, it is considered chronic. For many patients, everyday movements can provoke sudden flare-ups that make an already difficult condition even harder to manage.
Although the brain plays a central role in how pain is experienced, researchers have struggled to identify the precise brain circuits responsible for pain triggered by movement.
Chronic Back Pain Activates the Brain's Sense of Self
The new study, published on October 5, 2026, in the British Journal of Anaesthesia, identified an unexpected response involving the brain's Default Mode Network (DMN).
Sometimes called the "self network," the DMN consists of interconnected regions in the frontal, parietal, and temporal lobes. These areas are especially active when our attention turns inward, such as when we reflect on personal experiences, think about our identity, or consider our thoughts and emotions. In contrast, the network generally becomes less active when we direct our attention toward something happening around us.
The researchers discovered that sudden back pain caused by movement switched this network on rather than off. This unusual response suggests that chronic pain involves more than the processing of physical sensations. It may also engage the brain systems that shape how people experience themselves.
The findings could help researchers understand why treatments that focus primarily on suppressing pain symptoms do not always work well for chronic low back pain. They also raise the possibility that targeting the DMN could offer a different approach to treatment.
Brain Scans Reveal a Surprising Difference Between Chronic and Acute Pain
To investigate what happens in the brain during a pain flare, the researchers recruited 114 patients with chronic low back pain.
Each participant completed a "leg raise test," a standard clinical procedure used to provoke back pain. During the test, researchers monitored changes in brain blood flow using a specialized functional MRI method called arterial spin labeling. This technique allows scientists to track patterns of brain activity by measuring blood flow without relying on an injected contrast agent.
The team also examined how participants responded to a separate painful stimulus. They applied a harmless but uncomfortable heat sensation to the calf, similar to the brief pain someone might experience when accidentally touching a hot stove.
Comparing these two situations revealed a striking difference.
When movement triggered a flare of chronic back pain, the DMN became more active. However, when participants experienced the painful heat stimulus, the same network became less active, following the brain's typical response to acute pain.
The researchers also identified several other important patterns:
- Patients with more severe chronic back pain showed stronger connections between the DMN and the primary somatosensory cortex, a brain region responsible for processing physical sensations, including signals from the back.
- Greater pain intensity during the leg raise test was associated with increased activity in brain regions involved in sensation and movement.
- Increases in heart rate during the test reliably reflected the intensity of the pain flare.
Together, these findings provide new evidence that chronic pain flares involve brain processes associated with personal identity, not just the physical experience of pain.
Why the Brain Reacts Differently to Chronic Pain
During ordinary acute pain, the brain generally reduces activity in the DMN so it can concentrate on the immediate source of danger. This response helps shift attention away from internal thoughts and toward an external threat.
But the UC San Diego researchers found that movement triggered chronic back pain produced the opposite effect.
"In every pain study, when you're experiencing pain, the DMN deactivates," said corresponding author Fadel Zeidan, PhD, professor in the Department of Anesthesiology, endowed professor at the Sanford Institute for Empathy and Compassion, and director of the Pain Health and Mindfulness Laboratory at UC San Diego School of Medicine. "What we show for the first time ever is that when you have a pain flare, it turns on instead. You start to identify the experience with who you are."
Source: ScienceDaily
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