Low-intensity focused ultrasound to the insula and dorsal anterior cingulate has site-specific and pressure dependent effects on pain during measures of central sensitization
Background: The insula and dorsal anterior cingulate cortex (dACC) are core brain regions involved in pain processing and central sensitization, a shared mechanism across various chronic pain conditions. Methods to modulate these regions may serve to reduce central sensitization, though it is unclear which target may be most efficacious for different measures of central sensitization. Objective/Hypothesis: Investigate the effect of low-intensity focused ultrasound (LIFU) pressure to the anterior insula (AI), posterior insula (PI) or dACC on conditioned pain modulation (CPM) and temporal summation of pain (TSP). Methods: N = 16 volunteers underwent TSP and CPM pain tasks pre/post a 10 minute LIFU intervention to either the AI, PI, dACC or Sham stimulation. Pain ratings were collected pre/post LIFU. Results: LIFU to the PI significantly attenuated pain ratings in both TSP and the CPM protocols. LIFU to the dACC only affected TSP pain ratings. LIFU to AI had no effect on either TSP or CPM pain ratings. LIFU pressure modulated group means but did not affect overall group differences. Conclusions: LIFU to the PI and dACC differentially affected central sensitization. This may, in part, be due to dosing (pressure) of LIFU. Inhibition of the PI with LIFU may be a future potential therapy in chronic pain populations demonstrating central sensitization. The minimal effective dose of LIFU for efficacious neuromodulation will help to translate LIFU for therapeutic options.