Stable Mechanoreceptive Somatotopy in Chronic Low Back Pain: Is Cortical Map Reorganization a Myth?

Clinical Snapshot

Key Findings

• P Value: Not reported in abstract

• Effect Size: Not reported in abstract

• Primary Outcome: No significant differences in cortical somatotopic representation patterns between CLBP patients and healthy controls

• Nnt Or Sensitivity: Machine learning classifier accurately predicted upper vs lower back input in CLBP patients when trained on healthy controls

• Confidence Interval: Not reported in abstract

Clinical Application

Research-grade fMRI not routinely available; findings inform theoretical understanding rather than direct clinical application Relevant to Australian CLBP management guidelines; challenges assumptions underlying some rehabilitation approaches targeting cortical reorganization Adults with chronic low back pain presenting to primary care, pain clinics, or specialist services

Abstract

Chronic low back pain (CLBP) has been linked to maladaptive cortical plasticity in sensorimotor regions, which may contribute to pain persistence through less distinct ("smudged") somatotopic maps of afferent input from the back. However, empirical support for such functional reorganization, especially in the primary somatosensory cortex (S1), is limited. To delineate precise sensory representations of the back in humans and test for altered somatotopic processing in CLBP, we utilized an MR-compatible pneumatic vibration device and applied frequency-specific vibrotactile stimuli at nine thoracolumbar paraspinal sites in 45 patients with CLBP and 41 healthy controls (53 females in total). Representational similarity analysis was employed via a whole-brain searchlight method, and the neural representational patterns were contrasted against theoretical models including a segmental (based on anatomical proximity), simple (upper vs lower back division), and a random model. In addition, a machine learning classifier was trained to predict afferent input from the upper versus lower back in healthy controls and tested in CLBP patients. Both groups displayed well-organized segmental representations spanning somatosensory, motor, and posterior parietal cortices. Posterior parietal regions exhibited the best model fits, followed by S1. No evidence for differences in representational patterns between groups was found. In CLBP patients, these patterns did not show associations with pain duration, severity, and self-reported back perception. The classifier, trained on healthy controls, accurately predicted upper versus lower back afferent input in CLBP patients. These findings indicate preserved cortical maps of the back in CLBP, challenging the hypothesis of sensory cortical reorganization in this condition.

References

1. 1.Dörig, M., Cole, D. M., Guekos, A., Stämpfli, P., Schütz, P., Schibli, L., Schweinhardt, P., & Meier, M. L. (2026). Stable mechanoreceptive somatotopy in chronic low back pain: Is cortical map reorganization a myth? The Journal of Neuroscience. https://doi.org/10.1038/nrn2776