Non-invasive modulation of the human dorsal anterior cingulate attenuates acute pain perception and homeostatic cardiovascular responses

Abstract

Homeostasis is the process of maintaining physiologic balance in the body that is critical for maintaining health and is dysfunctional in several disorders like chronic pain. The dorsal anterior cingulate cortex (dACC) is a critical brain area for homeostatic cardiovascular responses and pain processing, making it a promising non-invasive therapeutic target. We leverage the high spatial resolution and deep focal lengths of low-intensity focused ultrasound (LIFU) to non-invasively modulate the dACC for an effect on behavioral and cardiac autonomic responses using a transient heat pain stimulus. N = 16 healthy human volunteers (6M/10F) received transient contact heat pain during either LIFU to the dACC or Sham stimulation. Continuous electroencephalogram (EEG), electrocardiogram (ECG), and electrodermal response (EDR) were recorded. Outcome measures included perceived pain ratings, homeostatic measures including heart-rate variability, blood pressure, EDR response as well as the amplitude of the contact heat-evoked potential (CHEP). LIFU reduced pain ratings by 1.08 {+/-} 0.21 points relative to Sham. LIFU increased heart rate variability indexed by the standard deviation of normal sinus beats (SDNN), low frequency (LF) power, and the low-frequency/high-frequency (LF/HF) ratio. There were no effects on blood pressure or EDR. LIFU resulted in a 25.1% reduction in the N1-P1 CHEP amplitude driven primarily by effects on the P1 amplitude. Our results demonstrate LIFU to the dACC reduces perceived pain and alters homeostatic cardiovascular responses to a transient heat pain stimulus. These results have implications for the causal understanding of human pain and autonomic processing in the dACC and the potential for future therapeutics for pain relief and homeostatic modulation. SIGNIFICANCE STATEMENTNew lines of inquiry now demonstrate cardiac homeostatic signals like heart rate variability (HRV) are aberrant in mental health disorders, addiction, and chronic pain and may contribute to their underlying etiology. The dorsal anterior cingulate cortex (dACC) is a key homeostatic center with direct influences on cardiovascular autonomic function, but its depth precludes direct access without invasive surgery. For the first time in humans, we demonstrate low-intensity focused ultrasound (LIFU) can non-invasively and selectively modulate the dACC to reduce acute pain perception and homeostatic cardiovascular responses as well as pain processing signals. This work helps establish a causal role of the dACC in pain perception and homeostatic signaling with potential future clinical applications in chronic pain and neuropsychological populations.