Researchers at UC San Diego School of Medicine have found that movement-evoked pain in chronic low back pain (cLBP) patients activates the brain’s default mode network (DMN), providing new insight into why this condition is so difficult to treat. The findings are published in the British Journal of Anaesthesia.
The DMN, often called the “self network,” becomes active when people think about themselves, their identity, or reflect on internal thoughts and feelings. This is the opposite of the brain’s typical response to acute pain, where the DMN shuts down to allow focus on the external threat.
In the study, 114 cLBP patients performed a leg raise test to trigger a pain flare while researchers measured brain blood flow using functional MRI. When participants experienced movement-evoked pain, their DMN activated rather than deactivated. In contrast, when the same participants were subjected to an acute heat stimulus, their DMN shut down as expected.
The researchers also found that patients with more severe chronic back pain had stronger connections between the DMN and the primary somatosensory cortex, which processes sensations from the back.
These findings suggest that chronic pain becomes deeply embedded in the sense of self, which may explain why standard treatments like opiates often fail for cLBP. The brain appears to couple physical pain with identity, contaminating moment-to-moment experience with anticipation, past experiences, and fear of movement.
The research team is now investigating whether approaches such as mindfulness meditation and psilocybin could help patients separate the physical experience of chronic pain from their identity, potentially offering new treatment pathways.
Source: Gianola M et al. Brain mechanisms supporting movement-evoked chronic low back pain: an observational brain imaging study. British Journal of Anaesthesia (2026). DOI: 10.1016/j.bja.2026.08.010
