Brains Control Pain Differently, Depending Where It’s Felt
/By Crystal Lindell
Different parts of the brain are more active when relieving pain — depending on where the pain originates — according to a new Australian study. The finding could lead to more targeted and effective treatments that utilize the body’s own pain relief system.
Researchers at the University of Sydney made the discovery while studying the placebo effect. They used MRI brain scans to monitor 93 healthy participants, while exposing them to painful heat on various parts of the face, forearm and leg.
Before the test, participants were given a placebo analgesic cream and told it would help relieve their pain. In reality, the “lidocaine” cream was a placebo and researchers secretly lowered the temperature of the heat, tricking the participants to believe the cream was easing their pain.
The heat stimulus was applied to the placebo-treated area, as well as a separate untreated area for comparison. Up to 61% of participants reported less pain in the area where the cream was applied, typical of a placebo response.
The MRI scans showed how the brain responded to the placebo effect. Researchers found that upper parts of the brainstem were more active when relieving facial pain, while lower regions of the brainstem were engaged for arm or leg pain.
“This is the first time we’ve seen such a precise and detailed pain map in the human brainstem, showing us that it tailors pain relief to the specific part of the body that’s experiencing it,” lead author Lewis Crawford, PhD, a Research Fellow at the University of Sydney, said in a press release.
Understanding which brainstem areas are linked to different parts of the body may open new avenues for developing non-invasive therapies that reduce pain.
“The brain’s natural pain relief system is more nuanced than we thought,” said Crawford. “Essentially, it has a built-in system to control pain in specific areas. It’s not just turning pain off everywhere; but working in a highly coordinated, anatomically precise system.”
“We now have a blueprint for how the brain controls pain in a spatially organised way,” said senior author Luke Henderson, PhD, a Professor in the School of Medical Sciences and the Brain and Mind Centre. “This could help us design more effective and personalised treatments, especially for people with chronic pain in a specific area of their body.”
It is important to note that none of the “healthy” participants had chronic pain, and thus these results may only apply to short-term, acute pain that is treated with a placebo.
Nevertheless, the study challenges long-held assumptions about how pain relief works. Instead of relying on medications that target opioid pain receptors in the brain, researchers say receptors in the brainstem could be targeted with cannabinoids.
“Opioid-based pain relief typically activates central areas of the brain and can affect the whole body, whereas the cannabinoid circuit that we identified appears to operate in more targeted regions of the brainstem,” said Crawford. “This supports the idea that cannabinoids may play a role in localised, non-opioid pain control.”
Most oral pain medications today – including acetaminophen, ibuprofen and opioids – work by telling the brain to relieve pain throughout the entire body. This research opens the door to more targeted therapies that relieve pain in specific parts of the body.
