Chewing or breathing sounds make you seethe? Blame your brain

For many people, the sounds of slurping coffee or crunching on an apple can be mildly annoying. But it can leave others seething. And their rage is very real, a new study finds. Certain sounds — especially eating, drinking and breathing — can boost activity in parts of the brain that deal with emotions. This can turn on a strong emotional reaction, leading to anger or anxiety.

For such people, the brain gives extra importance to certain sounds, says Sukhbinder Kumar. He’s a cognitive neuroscientist in England at Newcastle University’s medical school.  What is not clear, he adds, is why only certain sounds trigger this reaction.

His team described its new findings February 2 in Current Biology.

This intense sensitivity to some sounds is called misophonia (Mees-oh-FOH-nee-uh). The term means “hatred of sound.” Researchers aren’t sure how common the condition is. One study of college students, however, found that it afflicted nearly one in every five people tested.

Many people view those with misophonia as being just too sensitive to sounds, notes Jennifer Jo Brout. A psychologist at Duke University Medical Center in Durham, N.C., she was not involved with the  study. In fact, she says, the new work “really confirms that it’s neurologically based,” says Brout. By that she means that it is caused by certain physical structures or activities in the brain.

In the new study, researchers had 42 volunteers listen to various sounds while inside a brain scanner. This device let researchers view the activity in different brain areas. Twenty volunteers had misophonia; 22 didn’t.

Somesounds the recruits heard were neutral, such as rainfall. Others, such as a wailing baby, tend to annoy most people. A third set were chosen because they were known to especially bug people with misophonia. These included the sounds of chewing and breathing.

Both groups of people reacted similarly to the neutral and annoying sounds. But only the misophonics responded dramatically to chewing and breathing sounds. Their brain scans also showed a boost of activity after such sounds in an area known as the anterior insular cortex. This structure plays a role in processing emotions. Kumar’s group also found more connections among regions that help with processing emotions.

What’s more, people with misophonia showed an increased heart rate. Their skin was more electrically conductive, too. Such skin conductivity tends to rise when emotions are high. It’s part of the same sort of fight-or-flight response that gets triggered when facing a wild animal or speaking in public. And those, of course, are also very stressful situations.