Neural correlates underlying high-frequency stimulation-induced secondary hyperalgesia in humans

Area of Science:

• Neuroscience
• Pain Research
• Medical Imaging

Background:

• Central sensitisation (CS) is a key mechanism in chronic pain, involving heightened responses to stimuli.
• High-frequency electrical stimulation (HFS) is used to experimentally induce CS.
• The precise neural mechanisms underlying HFS-induced CS require further elucidation.

Purpose of the Study:

• To investigate the neural correlates of HFS-induced CS in healthy humans.
• To utilize functional magnetic resonance imaging (fMRI) to map brain activity changes.
• To identify brain regions and connectivity patterns associated with HFS-induced hyperalgesia.

Main Methods:

• Eighteen healthy participants underwent fMRI scans before and after HFS.
• Neural activity was measured during noxious punctate stimulation in the secondary hyperalgesia area and during rest.
• Whole-brain analysis and seed-based functional connectivity analysis (using periaqueductal grey and nucleus cuneiformis seeds) were performed.

Main Results:

• HFS induced significant hyperalgesia and increased neural activity in pain-processing regions (insula, cingulate cortex, thalamus, nucleus cuneiformis).
• Functional connectivity between the periaqueductal grey and pain-related cortical areas (insula, S2) was reduced post-HFS.
• These findings reveal specific brain activity and connectivity changes associated with experimental CS.

Conclusions:

• Neural correlates of HFS-induced CS align with other experimental models like capsaicin.
• Increased nucleus cuneiformis activity is a consistent finding in CS models.
• Altered functional connectivity suggests a shift in descending pain modulation, favoring facilitation over inhibition.