Acupuncture needling sensation: The neural correlates of deqi using fMRI

This pioneering study investigated the neural bases of the deqi sensation, considered fundamental in the traditional practice of acupuncture, using functional magnetic resonance imaging to map brain activity during different types of needle stimulation. The research was motivated by the importance acupuncturists attribute to obtaining deqi during treatment, although the underlying neurologic mechanisms remained poorly understood. The researchers recruited 17 healthy adults with no prior experience with acupuncture and performed needling at LI-4 (Hegu) on the right side, varying the depth between superficial (1-2 mm) and deep (8-12 mm). During the 16-minute sessions, participants underwent two 2-minute stimulation periods, with needle rotation at 2 Hz, while their brain activity was monitored by fMRI.

After each session, participants rated their sensations using a standardized questionnaire that differentiated between deqi sensations (such as numbness, heaviness, irradiation) and acute pain (such as burning, prickling, electric shock). The results revealed distinct neural patterns between the two types of sensation. When deqi sensations predominated, the brain showed only deactivations (decrease in BOLD signal) without significant activations, particularly in limbic and subcortical structures such as the hippocampus, amygdala, thalamus, and insula, as well as the cerebellum. In contrast, when acute pain sensations predominated, a combination of brain activations and deactivations was observed.

Direct comparative analysis between deqi and pain revealed that brain areas involved in pain and emotion processing showed lower activity during deqi compared with acute pain. These findings have important implications for understanding the therapeutic mechanisms of acupuncture. Deactivations in limbic and subcortical structures during deqi may represent a neurologic mechanism by which acupuncture produces its analgesic and therapeutic effects. The involvement of these areas, known to process pain, emotion, and stress, suggests that deqi may modulate neural circuits in a beneficial way.

The study demonstrates the importance of considering specific needle sensations in neuroimaging research on acupuncture, as different sensations produce distinct neural patterns that may confound results if not adequately controlled. Limitations include the relatively small sample size, the use of healthy participants without clinical conditions, and an experimental protocol that may not fully reflect real clinical practice. In addition, the prolonged stimulation periods (2 minutes) may have contributed to the pain sensations reported by participants. Despite these limitations, the study provides objective neurologic evidence for the traditional distinction between deqi and pain in acupuncture, offering a scientific basis for established clinical practices and direction for future research on acupuncture mechanisms.