Why the sound of noisy eating fills some people with rage

Imagine feeling angry or upset whenever you hear a certain everyday sound. It’s a condition called misophonia, and we know little about its causes. Now there’s evidence that misophonics show distinctive brain activity whenever they hear their trigger sounds, a finding that could help devise coping strategies and treatments.

“People who suffer from misophonia often have to make adjustments to their lives, just to function,” says Miren Edelstein at the University of California, San Diego. “Misophonia seems so odd that it’s difficult to appreciate how disabling it can be,” says her colleague, V. S. Ramachandran.

The condition was first given the name misophonia in 2000, but until 2013, there had only been two case studies published. More recently, clear evidence has emerged that misophonia isn’t a symptom of other conditions, such as obsessive compulsive disorder, nor is it a matter of being oversensitive to other people’s bad manners.

Some studies, including work by Ramachandran and Edelstein, have found that trigger sounds spur a full fight-or-flight response in people with misophonia.

Now it seems there may be a neurological explanation for this. Sukhbinder Kumar and his team at Newcastle University, UK, carried out a series of tests on 20 volunteers with a severe form of misophonia, as well as 22 people who don’t have it. Both groups listened to neutral noises, like the sound of rain; unpleasant sounds, such as a baby crying; and sounds that were triggers for the misophonics, such as chewing or breathing noises. While both groups reacted to the neutral and unpleasant sounds in a similar way, the misophonic group experienced increased heart rates and skin conductance – both signs of the body’s fight-or-flight response – when they heard trigger sounds.

Brain scans revealed that the misophonics had heightened activity in the anterior insular cortex (AIC), an area known to play a central role in the system that determines which things we should pay attention to. When the trigger sounds were played, there was not only more activity in this region but also abnormally high levels of connectivity to other regions. “The AIC is hyperconnected to structures that are involved in emotion regulating and memory,” says Kumar.

There was also increased connectivity to regions involved in the default mode network, which helps summon memories and processes internally generated thoughts. In misophonics, one of these regions, called the ventromedial prefrontal cortex (vmPFC), had a higher level of myelination – fatty sheaths that surround nerve cells and help conduct their signals – which may explain the greater connectivity.

Together, these findings suggest that the systems that normally influence what we pay attention to, and respond to emotionally, are disrupted in people with misophonia.

“I am hopeful that, in addition to providing powerful validation to sufferers of misophonia, this study will inspire a new wave of research on this topic,” says Edelstein.