It seems that the brain may have an ‘off switch’ for pain. Researchers at Duke University have found a small area of the brain in mice that can control the animals’ sense of pain.
The ‘switch’ is located in the amygdala, an area of the brain more often considered the home of negative emotions and responses, like the fight or flight response, or general feelings of anxiety. Mice have a relatively larger central amygdala than humans, but the team says the system for controlling pain is likely to be similar.
“People do believe there is a central place to relieve pain, that's why placebos work,” said senior author Prof Fan Wang. “The question is where in the brain is the centre that can turn off pain.
"Most of the previous studies have focused on which regions are turned on by pain. But there are so many regions processing pain, you'd have to turn them all off to stop pain. Whereas this one centre can turn off the pain by itself.”
The researchers found they could ‘switch off’ the behaviours a mouse exhibits when it feels uncomfortable by activating its CeAga neurons, a region of neurons found in the amygdala. They did this using a technology called optogenetics, which uses light to activate a small population of cells in the brain.
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The mice under test completely stopped licking their paws and wiping their faces, behaviours they commonly display when agitated, as soon as the light was switched on to activate the anti-pain centre.
“It's so drastic,” Prof Wang said. “They just instantaneously stop licking and rubbing.”
The researchers are hoping to use the findings to create a new kind of painkilling drug.
Reader Q&A: Could painkillers also kill pleasure?Asked by: Henry Parr, Frome
A couple of recent studies at the Ohio State University suggested that painkillers can blunt feelings of pleasure as well as pain. The researchers found that one 1,000mg dose of paracetamol could reduce the pleasure experienced from looking at heart-warming pictures, or reading short stories about someone having good luck.
It may be that paracetamol affects signalling processes in the brain linked to mood. However, the studies had a limited scope – focusing on students in a lab – making it difficult to equate with real-life settings.
Jason is the commissioning editor for BBC Science Focus. He holds an MSc in physics and was named Section Editor of the Year by the British Society of Magazine Editors in 2019. He has been reporting on science and technology for more than a decade. During this time, he's walked the tunnels of the Large Hadron Collider, watched Stephen Hawking deliver his Reith Lecture on Black Holes and reported on everything from simulation universes to dancing cockatoos. He looks after the magazine’s and website’s news sections and makes regular appearances on the Instant Genius Podcast.