By targeting the various physiological pathways of our body, acupuncture stimulates the central nervous system. This relationship produces biochemical changes that may affect neurotransmitters in muscles, the spinal cord, and the brain.
To visualize the effects directly in the brain, researchers have performed fMRIs (functional magnetic resonance imaging) on those undergoing acupuncture treatment.
Patient preparing for an fMRI
These colorful images highlight the areas in the brain undergoing the highest levels of metabolic activity and thus reflect the areas of the brain that are in use. For example, when you are talking, your Broca’s area, the area of the brain responsible for speech production, lights up.
Researchers have found that acupuncture is responsible for affecting a variety of areas in the brain. For example, two-thirds of studies assessed by a systematic review and meta-analysis in 2012 found acupuncture to increase activity in the motor areas, basal ganglia, cerebellum, the prefrontal cortex, and the limbic system.
Three of the 25 studies showed decreased activity in the limbic system, which is responsible for a collection of primal behavioral and emotional responses.
Another interesting finding was that patients respond differently to the same acupuncture points.
For example, a clinical study in 2005 found that patients with Alzheimer’s disease had more activation in the cingulate gyrus and the cerebellum while a clinical trial in 2007 found individuals who were heroin addicts to have increased activation in the hypothalamus. These results differed from the areas lit up in the studies’ healthy controls.
Acupoints Specific to Points in the Brain
Parts of the brain specific to varying functions
While it has been understood that acupuncture can elicit responses in the brain, a more focused question is whether specific acupoints can produce responses in specific regions of the brain that connect to their intended therapeutic effect.
Many acupuncture points have associated therapeutic effects on target organ systems. Can these effects be seen in the brain?
To evaluate whether the stimulation of specific acupuncture points correlated to specific areas of the brain, a randomized controlled study in 2008 performed varying acupoints on healthy subjects. The scientists placed half of the subjects in a sham group to measure whether the fMRI responses were due to the acupuncture.
Four of the acupoints activated two specific areas of the brain: the bilateral primary somatosensory area and the ipsilateral cerebellum. These points are on the same meridian, suggesting that points on the same meridian (acupuncture channel) may activate similar areas of the brain. These common responses were not seen in the sham group patients.
Altering Pain in the Brain Revealed through fMRI
A clinical study in 2019 compared fMRI imaging in Parkinson’s Disease patients after acupuncture treatment or no acupuncture (control). A collaboration of seven universities in Taiwan and King’s College in London notably completed this study. Outside of the acupuncture, all participants received the same medication.
The goal of the acupuncture treatments was to reduce the pain experienced by Parkinson’s Disease. The researchers hypothesized that fMRI results between the two groups would show different brain activity in areas of the brain that processed pain.
The study completed fMRIs on the patients after either the treatment or the control in addition to after a three-month wash-out period for the acupuncture-treated group. In comparison to the control group, the fMRIs in the treatment group had altered brain connectivity within the pain-related neural networks.
Additionally, to measure whether the acupuncture was effective in reducing pain, the researchers assessed pain using the King’s Parkinson’s Disease Pain score. The acupuncture group had a reduction of 46.2% in their pain score after acupuncture compared with the control group.
To further understand how acupuncture could produce pain relief, a clinical study in 2014 explored how repeated acupuncture stimulation affected pain-related areas of the brain. Many studies analyze the immediate effects of acupuncture in the brain, but not the cumulative effect from long-term exposure.
Forty health volunteers received repeated acupuncture for 40 minutes at the acupoint Zusanli (ST36) alongside three fMRIs.
The areas of the brain involved in pain processing included the motor cortex and the somatosensory cortex. After the initial acupuncture session, areas within these cortexes showed stimulation on the fMRIs.
These findings were expected because acupuncture stimulation can produce variations of pain sensations. How do these areas actually process pain? The middle cingulate cortex plays a role in distracting an individual from expecting pain, the thalamus helps communicate pain (nociceptive) information to the cerebral cortex, and the motor cortical areas may be involved in pain-producing movements.
Overall, the study found the strength of the brain responses to be time-dependent. What that means is that the response on the fMRIs produced by the first response was the strongest and the last treatment produced the weakest response.
The areas in the brain activated included those consistent with previous acupuncture fMRI studies. The habituation results shown suggested a decreased pain perception. These results explain how over time, one might feel an analgesic response to acupuncture, not the idea of the pain that needles typically elicit.
Strengthening the Brain
Through stimulation, acupuncture may improve motor function in patients with damaged motor cortexes. A randomized controlled study in 2007 evaluated acupuncture in patients with chronic hemiparetic stroke.
The sham-controlled study included a 10-week acupuncture protocol in patients with chronic hemiparetic stroke. The patients who received acupuncture had greater activation and modulation in their motor cortical areas of the brain in comparison to those with sham acupuncture.
The goal of this stimulation was to improve the function of affected upper limbs that had been compromised by a stroke. While the sample size of the study was small, the scientists concluded that acupuncture could improve the function of the affected upper limb due to increased activity in the ipsilesional motor cortex.
To look at another condition, a randomized controlled study in 2020 explored whether acupuncture could strengthen the brain to support patients with primary insomnia. Patients were randomly assigned to 5-weeks of either single-point or multiple-point acupuncture or a participate in the sham group.
The goal of acupuncture was to impact regions of the brain involved in the quality of sleep. The fMRI results revealed a positive change in brain activity during rest in the acupuncture group.
Furthermore, the combination of multiple acupoints impacted a greater number of regions. The scientists are hoping to expand on this study to explore how the combination of multiple acupoints could improve the therapeutic effect of acupuncture in insomniacs.
These two studies are only one bit of the data revealing the ability of acupuncture to be involved in the neuroplasticity of the brain. Neuroplasticity explains the ability of a brain to grow and strengthen over time.
To quickly note on two more studies, a randomized controlled study in 2020 found acupuncture to help strengthen connections within the primary somatosensory cortex. This modulation helped improve tactile acuity, which had been compromised in patients with chronic low back pain.
And an earlier randomized controlled study in 2017, found similar activity in the primary somatosensory cortex, which helped improve long-term outcomes of those with carpal tunnel syndrome.
What exactly do these fMRIs show us?
Based on the above research, fMRIs are visual representations of acupuncture’s effects on our bodies. Our brains can have therapeutic responses to specific acupoints, these responses vary based on the conditions of our brains, and these responses also depend on whether an acupuncture treatment is our first or not.
These “maps” of the effects of acupuncture are both pieces of art as well as exciting data portraying the therapeutic potential.