Effects of Electroacupuncture versus Manual Acupuncture on the Human Brain as Measured by fMRI

Acupuncture is an ancient practice that has been drawing growing scientific interest, especially regarding the mechanisms by which it produces its therapeutic effects on the central nervous system. Traditionally, there are two main modalities of this technique: manual acupuncture, which uses needles inserted into specific points on the body with manipulation through rotation and lifting movements, and electroacupuncture, a more modern technique in which electrical current is applied through the needles. Although manual acupuncture has more than 2,000 years of history, electroacupuncture offers the advantage of allowing precise control of stimulus intensity and frequency, which are essential for scientific research and controlled clinical application.

This pioneering study aimed to compare the effects of different acupuncture modalities on the human brain using functional magnetic resonance imaging, an advanced imaging technique that allows brain activity to be observed in real time. The researchers recruited 13 healthy volunteers who had never experienced acupuncture, thereby eliminating possible influences from prior experience on the results. Each participant underwent four different types of stimulus at point ST-36, located on the leg: traditional manual acupuncture, low-frequency electroacupuncture (2 Hz), high-frequency electroacupuncture (100 Hz), and a tactile control consisting of gentle skin touches without needle penetration. The experimental protocol was carefully designed, with rest periods interspersed between stimulation sessions, allowing the brain to return to a baseline state before each new intervention.

The results revealed significant differences between the acupuncture modalities and important similarities that distinguish them all from the tactile control. Electroacupuncture, particularly at low frequency, produced broader and more intense brain activation compared with manual acupuncture, with positive responses observed in 15 distinct brain regions for 2 Hz electroacupuncture, nine regions for 100 Hz, and only seven regions for manual acupuncture. All forms of acupuncture produced a characteristic pattern of brain activation involving the limbic system, a region fundamental to the processing of emotions, pain, and regulatory functions of the body. Specifically, decreased activity was observed in structures such as the amygdala, anterior hippocampus, and subgenual cingulate cortex, areas traditionally associated with the processing of pain and stress.

At the same time, there was increased activity in the anterior insula, an important region for sensory perception, and in the secondary somatosensory cortex, an area that processes tactile information. Low-frequency electroacupuncture also showed specific activation in the pons, a brainstem region rich in serotonergic neurons, suggesting the involvement of specific neurochemical systems.

These findings have important implications for patients and healthcare professionals. First, they confirm that acupuncture produces real and measurable effects in the brain, clearly differentiating it from a simple placebo tactile stimulus. The activation pattern observed suggests that acupuncture can effectively modulate neural circuits involved in pain processing and emotional regulation, providing a scientific basis for its use in the treatment of conditions such as chronic pain, anxiety, and mood disorders. The discovery that different electroacupuncture frequencies activate slightly distinct circuits suggests that modality choice can be personalized according to the condition being treated.

For example, low-frequency electroacupuncture, by activating serotonergic systems, may be more effective for mood-related conditions, while higher frequencies may be preferable for other types of pain. For clinicians, these results provide scientific guidance for selecting the most appropriate technique, allowing therapeutic decisions to be made on the basis of objective evidence rather than mere empirical tradition.

It is important to recognize some limitations of this study that should be considered when interpreting the results. The sample size was relatively small, and some participants had to be excluded because of excessive movement during the scans, a common challenge in neuroimaging studies. In addition, all volunteers were acupuncture-naive, which, although it eliminates prior-experience bias, may not fully reflect the responses of patients in actual treatment. The study was also limited to a single acupuncture point and a single treatment session, while clinical practice generally uses multiple points in prolonged treatments.

Future studies should include larger samples, longer treatment protocols, and investigate different acupuncture points to confirm and expand these findings. Despite these limitations, this research represents an important advance in the scientific understanding of acupuncture, demonstrating for the first time that different modalities produce distinct patterns of brain activation and providing robust neurobiological evidence for the therapeutic effects of this ancient medical practice.