Placebos work on key brain circuits

A placebo may have a powerful effect, but in your brain, what does it look like? A new study has found that placebos can have a real effect on a person's brainstem, which is the center of pain management. This work could help scientists develop more effective treatments for chronic pain.

Ted Kaptchuk, a biomedical scientist at Harvard Medical School in the United States who was not involved in the study, said it was a "significant contribution to the field." Still, he cautions that more work is needed to explore whether the lab-based research can be practically applied.

Scientists knew about the placebo effect more than 400 years ago. In 1572, a French philosopher wrote: "For some people, medicine can work just by looking at it. However, researchers have struggled to understand why patients have eased after receiving non-aggressive treatments such as sugar pills. On the other hand, when patients are told that placebo has side effects, they tend to feel bad, the so-called "placebo" effect.

To identify the characteristics of these two effects in the brain, researchers at institutions such as the University of Melbourne in Australia recruited 27 participants — 13 men and 14 women, with an average age of 23. Scientists have tied a thermostat to their arms that is heated to a temperature that makes people feel moderately painful.

Afterward, the researchers told the participants that they were smeared with one of 3 plasters: painkillers, pain-inducing medications, and control plasters that didn't work. In fact, all 3 substances are Vaseline.

Meanwhile, the team scanned the volunteers with high-resolution functional magnetic resonance imaging to detect which part of their brain was most active. Most participants experienced either a placebo or abobo effect. About 1/3 of people reported lower levels of pain when using "painkillers," while slightly more than half reported worsening pain when using pain-inducing drugs.

Magnetic resonance imaging also showed these results. Researchers recently reported in the Journal of Neuroscience that both the placebo effect and the placebo effect affect the activity of the brainstem. The placebo effect increases the activity of the ventral medial area on the snouting side of the medulla that transmits pain messages, reducing the activity of the gray matter area around the catheter that helps the body suppress pain. The placebo effect caused the opposite change. The findings may seem counterintuitive, but the researchers say multiple areas of the brainstem play a role in complex ways when it comes to producing pain sensations.

Tor Wager, a neuroscientist at Dartmouth Who studies the placebo effect, says the approach is fantastic. "It was done at ultra-high resolution, which allows it to better identify the brainstem that plays a key role in pain control." While other studies have shown that brain activity responds to both placebo and placebo effects, he and other experts say the new study provides the most detailed understanding to date about how the brain responds to these phenomena.

Lewis Crawford, a neuroscientist at the University of Sydney and lead author of the study, said the findings could provide a pathway for treating chronic pain in the future.

Currently, doctors apply electrical impulses to the brainstem, a method known as deep brain stimulation that is used to treat burning "neuropathic" pain caused by nerve damage and carpal tunnel syndrome. But it has had only mixed effects for decades on cancer-related pain, such as invasion of nervous system tumors or nerve damage caused by radiation.

Part of the problem, Crawford says, is the inability to accurately identify which part of the brainstem is responsible for controlling the regulation of pain. By localizing the feelings caused by placebo and placebo to more precise brain regions, he said, the new study could help narrow the target of the stimulus. Whether it's a placebo or not, it's valuable good news. (Tang Yichen)

Source: China Science Daily