Research reveals why some find the sound of others eating so irritating
Scans show some brains have a stronger link between the part that processes sound and that which controls the mouth and throat
Scientists have shed light on why everyday sounds such as chewing, drinking and breathing can be so maddening to some people that it drives them to despair.
While the familiar munching and slurping of the dinner table are innocuous enough to most, those with misophonia – literally a hatred of sound – can find them profoundly irritating, to the point that they become disgusted, anxious, angry and even violent.
Now, brain scans performed by researchers at Newcastle University have revealed that people with misophonia have stronger connectivity between the part of the brain that processes sounds and the part of the so-called premotor cortex which handles mouth and throat muscle movements.
When people with misophonia were played a “trigger sound”, the scans showed that the brain region involved in mouth and throat movement was overactivated compared with a control group of volunteers who did not have the condition.
“What we are suggesting is that in misophonia the trigger sound activates the motor area even though the person is only listening to the sound,” said Dr Sukhbinder Kumar, a neuroscientist at Newcastle University. “It makes them feel like the sounds are intruding into them.”
Kumar and his colleagues believe that trigger sounds activate what is called the brain’s mirror neuron system. Mirror neurons are thought to fire when a person performs an action, but also when they see others make particular movements.
Activating the mirror neuron system with trigger sounds did not make people with misophonia involuntarily start chewing or swallowing. But the researchers believe it can produce an urge to through what they call “hyper-mirroring.” Dr Kumar said some people with the condition mimic the sound that sets them off because it brings them some comfort, perhaps by reasserting control over the sensations they feel.
If the finding reported in the Journal of Neuroscience stands up in future research, it could pave the way to more effective therapies for misophonia, which some patients find deeply unpleasant. Dr Kumar said the mirror neuron system can be trained, so it may be possible for people to break the link between a particular sound that drives them crazy and the distressing effects they experience. Research on undergraduate medics in the UK this year found that about 12% experienced moderate symptoms of misophonia, with 0.3% having a severe condition.
Tim Griffiths, professor of cognitive neurology at Newcastle, and a senior author on the study, said the work highlighted the importance of treating misophonia as more than a problem linked to the sound-processing regions of the brain, adding that effective therapies must consider the motor, or movement, regions too.