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One of the coolest and strangest things in medicine, some say, is the placebo effect: drugs that clearly contain no active ingredient or "fake" interventions that improve health just by "believing it works."
A classic example is the placebo effect of analgesics, and there are many clinical trials showing that "fake" painkillers or painkiller surgeries can actually relieve pain in patients, even in the same way as real surgeries.
Pain is an experience that the brain produces through complex neural activity. So, what happens in the brain when we use a placebo that makes us "fool ourselves"? A recent meta-analysis study published in Nature Communications, a sub-issue of Nature, answered this dilemma.
The scientists note that in order to find the neural mechanisms behind the placebo effect, there have been some small-scale studies in the past. Through the first large-scale meta-analysis, which focuses on analyzing the whole brain images of individual participants, it is possible to analyze in detail the various brain regions involved in the establishment of pain sensations, so as to gain a deeper understanding of the placebo effect.
To this end, the researchers synthesized 20 neuroimaging studies and examined in detail the brain activity of more than 600 healthy participants. All participants said they were "treated" to reduce pain, but the researchers wanted to find out if the brain responded to the placebo in a meaningful way. For example, did placebo change the way the brain feels pain, or did it change people's thinking about pain afterwards?
After analyzing large-scale samples, the researchers targeted the placebo effect to specific brain regions, such as the thalamus. The thalamus can be seen as a portal for various sensory inputs, such as vision and sound, and is made up of many nuclei, like different workstations, used to process different types of sensory input. The results showed that the nuclei most important for the treatment of pain were most strongly affected by placebo.
Another area of the brain that is essential for the early processing of pain information, the somatosensory cortex, is also affected by the placebo effect. In addition, the placebo effect affects the basal ganglia, a very important brain region that links pain to other experiences and behaviors. "Placebo reduces the amount of pain you experience, including feelings of pain and motivating you to take actions to avoid pain." Professor Tor Wager, who led the study, explains.
The study also found that placebo treatment reduced activity in the back of the brain lobe (insula), meaning that the pathways of pain formation were affected.
MRI shows that during pain, the activity of brain regions associated with constructing pain experiences (blue) is weakened, and the activity of brain regions (red and yellow) associated with cognition and memory is enhanced
Another area of interest is the prefrontal cortex, an important brain region associated with higher cognitive function. This area is activated when we anticipate pain, helping us to continuously track the context in which the pain occurred and to confirm the presence of the pain. But the researchers found that the activity of the prefrontal cortex was inconsistent across studies, and none of the specific areas were continuously activated. This suggests that factors such as the way placebo is administered, the way people think and think may affect the placebo effect.
"Overall, this suggests that the placebo effect is not limited to sensory (nociceptive) or cognitive (emotional) processes, but is more like a synthesis of multiple mechanisms, and therefore produces results that vary from person to person." Professor Wager said, "We hope these results can contribute to the development of brain biomarkers to predict how different people will respond to placebo, which helps distinguish the placebo effect from the analgesic response of the drug." ”
Scientists believe that understanding the neural mechanisms of the placebo effect is important for both clinical and drug development, and that when we combine specific contexts, target specific diseases, and use the placebo effect in a more effective way, we can ultimately lead to better treatment outcomes for patients.
Resources:
[1] Matthias Zunhammer et al., (2021) Meta-analysis of neural systems underlying placebo analgesia from individual participant fMRI data. Nature Communications. Doi: https://doi.org/10.1038/s41467-021-21179-3
[2] Study Provides Deep Dive on the Neuroscience of Placebo Effects. Retrieved March 3, 2021 from https://news.dartmouth.edu/news/2021/03/study-provides-deep-dive-neuroscience-placebo-effects
Note: This article is intended to introduce the progress of medical and health research, not to recommend treatment options. For guidance on treatment options, please visit a regular hospital.
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